Ask the Doctor


I am traveling to a time zone that is 12 hours ahead. I will be in that time zone for 12 days (traveling east to west). If I buy the sunglasses you recommend, how do I adjust the light or what time of day should I wear the sunglasses to overcome jet lag?

You’ve chosen to take on a most difficult challenge, given the huge degree of phase shift you’re trying to make your body do rapidly, and given the tiny chance of finding a non-stop flight for this route. The arduous travel of 30 hours alone makes this a challenge, even without jet lag. For such questions, I usually refer people to the book How to Beat Jet Lag: A Practical Guide for Air Travelers, published years ago by Walter Reich, Norman E. Rosenthal, Thomas A. Wehr, and me. It’s available for just pennies a copy (plus shipping) from Amazon at (Disclosure: the book is now officially out of print and the authors no longer receive any royalties.) For the specific trip you mention, you’ll want to avoid light before 10 AM on the first day of travel. From 9 PM – 3 AM (original time zone) you will want to stay awake and expose yourself to bright light. This will be a challenge because of the late hours when your body will likely be doing its best to drag you off to sleep. At 3 AM (original time) reset your watch to the destination time zone. Then after 4 pm (destination time) avoid light again. This is the start of inducing the phase delay that you will want for your westward travel. Your “time-light” efforts will continue for the next three days at your destination, and those details along with critical caveats and safety guidelines are detailed in the book I mentioned. ―Dan Oren, MD

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Hello, I have been using a light box for just over three weeks now. Initially I simply used it when I naturally woke-the first week was at the end of the summer holidays so average time to find myself sitting in front of the box was 9am. After about a week I discovered your website, took the AutoMEQ and discovered the time I needed to be using it was 530am. I weaned myself back to this time over the following 5 days. My principal drive for using light therapy is avoidance of SAD symptoms and so I based my overall time of initiation of therapy on my wish to avoid SAD creeping in at all this autumn; I actually feel that because of the dreadful summer Ireland has had this year, that my mood and energy levels did not get their customary boost during the ‘brighter’ months. So, my main question is, how long will it take to adjust my circadian rhythm to the point where waking at 5:15 happens without an alarm clock? Additionally, should I miss a morning (for example, at the weekend), does this cause disruption to the pattern I’m attempting to establish?

The difference between your spontaneous (late) wake-up at 9am and your goal, 530am, is large. The adjustment should be made more slowly. You should begin light therapy 30 minutes before your current wake-up time (in this case 830am), and stick with it until your wake-up has advanced by 30+ minutes. This may take several days, although sometimes it will happen in 1-2 days. At that point, shift light therapy another 30 min until you are stabilized at 8am. Continue this sequence until you reach 530 am, making sure you have adjusted comfortably at each step. It is possible that you will feel the full effect before reaching 530am, in which case you can maintain the later wake-up time (for example, 630am). Skipping a single day over the course of a week should not be seriously disruptive, but if you were routinely to skip whole weekends, your circadian clock will quickly shift later, and you may even have to back-track (for example, from 7am to 8am), if you have difficulty waking up on Monday morning, and proceed from the later hour.

Obviously, there is a risk of significantly slower adjustment if you skip days frequently. It would be helpful if you maintained a log (downloadable from Dropbox link, which will help you review your rate of progress and identify possible disruptive influences. Bottom line: if the AutoMEQ advises waking up for light therapy more the one hour before your current wake-up time, you should approach the goal in small steps, waiting to adjust at each step.

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I am taking St. John’s wort for depression. One of the well-known side effects is photosensitivity. Is this a concern when using a light therapy unit such as the Carex Health Brands or other models that filter out UV radiation?

Photosensitization is unusual when it comes to St. John’s Wort. While most photosensitizing meds react to UV (and sometimes also to blue light), St. John’s Wort — hypericum — photosensitizes to green light, right in the middle of the visual spectrum. Here is a case where the drug (or non-prescription “supplement”) should not be combined with bright light therapy, because the light contains a major green component. Since you are asking about adding light therapy to St. John’s Wort, we can guess that the drug is not doing an adequate job on its own. You may want to consider, then, whether light therapy does a better job — but also on its own. In other words, by all means try light therapy, but first discontinue use of St. John’s Wort at least until you make the assessment.

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Do my eyes have to be looking directly at my light box to get maximum benefit? I usually read or do computer work with my head straight, but my eyes looking down…is light still reaching the retina? Also, I wear glasses to read…will that affect the benefit of the light box?

Never look directly into a 10,000 lux light box — it will be glaringly intense, and quite unnecessary.  How you orient your head and eyes depends on what type light box you are using.  CET’s recommended model, the Day-Light Classic Plus,  was designed to direct light to your eyes from above the line of sight, thus illuminating the maximally sensitive lower portion of your retina.  You receive adequate stimulation by concentrating on the work area below the screen — reading, eating, phoning, texting, working on your laptop, and so on.  Wearing glasses is acceptable as long as they are not tinted. In other words,  clear glass or plastic lenses are fine.

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Is there an ideal number of minutes after actual sunrise for the earliest morning sun to have an optimal effect on SAD and circadian rhythm?

By “optimal effect,” we assume you mean antidepressant and circadian phase-advancing effects. 10,000 lux, the high-dose standard for white light therapy, occurs outdoors about forty minutes after sunrise.  But that’s too pat an answer.  Studies of dawn simulation show that antidepressant and circadian effects begin before sunrise.  Dawn is a continuous event that may last 90 minutes or longer.

Based on New York data, the average SAD patient experiences remission of winter depression during the first week of April, with sunrise around 6:30 AM.  There is a wide spread of dates across individuals, though.  In most cases, remission occurs as early as the spring equinox around March 20-22, with sunrise around 6:55 AM, and as late as the start of May, with sunrise around 5:45 AM.

These statistics indicate that a person’s chronotype (as determined by our AutoMEQ questionnaire) influences the time of day when sunrise — and the dawn that precedes it — will have optimal effect. Evening chronotypes may respond best to light therapy at 8 AM or later, while morning chronotypes may respond best at 5:30 AM or earlier.

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I have non-seasonal depression. How do I know the best time of day to use the light box? My mood is worst in the morning and improves as the day progresses especially if I get out of the house within an hour — or two the most — after waking up.

You’ve answered your own question, of course. Begin light therapy at a standard time, early in the morning. Ideally, do this as soon as possible after waking up, as the first activity of the day. If you are waking up too early — in the middle of the night — and can’t get back to back to sleep, keep room lights low, and use f.lux on your computer screen, blue-blocking glasses if you turn on the TV, and blue-blocking glasses or blue-free night-lights in the bathroom or kitchen. As Dr. Raymond Lam reported for his clinical trial of successful light therapy for non-seasonal depression, “Our study used a standard light therapy protocol that has been effective in SAD studies [10,000 lux early morning bright white light, for 30 minutes].” Until there are procedural elaborations based on further studies of light therapy for nonseasonal depression, Dr. Lam’s method is the way to go.

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I’m interested in trying negative air ionization therapy while I sleep, for depression which is treated with medication but not completely resolved. I also use a CPAP (continuous positive airway pressure) machine, so the air I breathe passes through a filter, over a humidifier chamber, and is heated in the tubing. Would the CPAP affect the negative air ions, and would ionization still be effective?

Most likely, the benefit of negative air ions would be lost while using CPAP.  Our current understanding is that the ionized air has to be inhaled, and routing it through the CPAP machine would likely neutralize it.  That said, there is no evidence that negative air ionization works preferentially during sleep.  Research studies have shown antidepressant efficacy both during sleep and waking hours.

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Are there contact lenses available that perform the same function as the blue-blocker glasses you recommend on your online store?

While tinted contacts have been around for years, none replicates the specifications of the Photonic Developments’ protective lenses. These protective lenses are used to assist sleep onset, to allow evening melatonin to exert its circadian rhythm shifting effect, and — in the most recent research — to calm hypomanic and manic symptoms of bipolar disorder.  Contacts are a good idea, and we will look into this possibility for future development. Thanks for asking!

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I am 34 years old and have a long history of difficulty sleeping. My doctor diagnosed me with delayed sleep phase disorder (DSPD). It appears that my “normal” sleep time is 4 or 5 a.m., and I typically wake up around noon or 1 p.m. I would like to shift my sleep earlier so that I can fall asleep around midnight or even 11 p.m. I purchased a light box per my doctor’s instructions, but he is not sure how/when to apply the light box. What time should I use the light box? Immediately upon waking at noon? If I do so any earlier, it will disrupt my sleep.

Each case of DSPD needs individual clinical consideration because multiple factors can cause the sleep pattern, and therefore approaches to treatment will vary.  Thus we can only suggest a broad strategy here.  Light therapy can start at your current wake-up time, as you say. However, waking up for light therapy half an hour earlier than usual may speed up progress.

In conjunction with morning light, it is critical to control bright white (and bluish) illumination for several hours before sleep. Ways to do this include using blue-blocking glasses, such as the protective lenses we recommend on our site. You can also install f.lux software, available for free, on your computer, and Night Shift software on your iPad and iPhone.  Room light should be kept low, but comfortable, allowing clear vision at a distance.  Refrain from eating for at least three hours before current, expected sleep onset.  

The bedroom should be dark, ideally with blackout shades for protection from the dawn twilight and early morning sunlight during hours you are sleeping. Given the darkness of the bedroom, it is helpful to set a bedside dawn simulator to provide increasing light, from darkness to maximum illumination, in the 30 minutes before you need to get up.  Set an alarm clock for back-up in case you don’t wake up spontaneously to the dawn signal.

If you are not oversleeping, after a few days, it will be time to begin shifting wake-up time progressively earlier, probably in 30-minute steps every 3-4 days.  Dawn simulation and post-awakening bright light therapy should be shifted together. Be careful not to rush the process. If you shift too rapidly, you may find yourself flipping into a delayed sleep pattern even more extreme than when you started. Therefore, the process requires close attention. Make sure you are waking up comfortably at each new wake-up time  before you try shifting your wake-up time 30 minutes earlier. Each 30-minute change may take just a few days, or require a week.

The dose of bright light therapy can make all the difference. The best length of time for a session at 10,000 lux can vary substantially between individuals. Thirty minutes will be effective for some people, but others will need 45 or even 60 minutes. Keep in mind that you may be successful at waking up earlier long before you are successful at falling asleep earlier to the same extent. Consequently, there may be an interval of days, or even weeks, when you don’t get as much sleep as usual.  At some point, however, you should be able to compensate for earlier waking with earlier bedtimes. Look for signs that you are starting to get sleepy earlier than expected, and yield to your sleepiness rather than continuing nighttime activities. However, don’t force yourself into bed before you get sleepy.  

Beyond this general strategy, you may also need to practice good sleep, or consider the influence of your medications on sleep.  

In short, you will be lucky if you can pull off this change on your own, without a clinician’s monitoring and guidance throughout. That said, many people have had such luck, and it is well worth the trial, even if it fails.  

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Would it be OK for me to simply replace all household lighting with full spectrum light bulbs, or are they too hot or something?

Replacing lighting with full spectrum light bulbs is not a good idea for two main reasons. Full spectrum light ― actually a deceptive advertising term, not a technical specification of lamp output ― becomes quite uncomfortable with prolonged exposure. That is due to the added short-wavelength radiation, which creates a bluish cast, and makes the lights cold and glaring.

While the added blue might help you become more alert after you wake up, it could also make you jittery and headachy during the day, and make it harder to fall asleep at bedtime.  Even standard “cool white” and “soft white” bulbs contain enough blue for use in morning light therapy, though their close positioning in a light box increases the intensity so you get far more light from them than you would get from standard room and ceiling fixtures.

If your goal is energizing light with an antidepressant effect, the way to go is a 10,000 lux light box that meets the safety criteria in our Therapy section.

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I am 60 years old. For 16 years I have successfully treated my Seasonal Affective Disorder (SAD) with light therapy and a low dose of Paxil.  My first signs are anxiety, sleep disruption, and social withdrawal.  This year the light therapy is not working, and I am a mess from depression and anxiety.  Does light therapy become ineffective?  I have tried changes, and new, clinically approved lights, with no help.  Any thoughts?

Sorry to hear that you’ve been having trouble maintaining good effect from your light + medication regimen. There could be numerous reasons, unfortunately impossible to sort out from the limited information in your note.  You give one possible clue, however, when you mention “low dose of Paxil.” Both meds and light lie on dosing dimensions, which can be manipulated separately or in concert.  Dosing of light involves three main factors: level of illumination at the eyes (lux), duration of the daily session, and timing of the session relative to your circadian rhythm. Take (or re-take) our Morningness-Eveningness (AutoMEQ) questionnaire to see if your treatment schedule is a good match to your rhythm. Consider increasing session duration in modest steps of about 10 minutes, with four days at each step to ascertain effect.  You should not go beyond a 60-minute session.  Make sure your sitting position at the light box is correct for receiving full 10,000 lux exposure.  If your doctor is recommending a Paxil dose increase, it is very important to do this in coordination with light dose adjustment, or you may start experiencing side effects.

Loss of effect may also be due to progressive eye problems typical at your age, so you should have a thorough ophthalmology check-up, and you should discuss your experience with light dosing with your ophthalmologist. If these steps don’t produce results, it will be time to seek a psychiatry consultation to probe other factors that may have led to this year’s turnaround after your years-long positive experience.

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Light therapy so far seems helpful for my depression, but I’ve noticed that it makes me feel anxious and wound up. Should I adjust the dosage of light by reducing the time? I’m doing 10,000 lux for around 25 minutes.

You should not have to suffer this “overdose” side effect to experience the antidepressant benefit of light therapy.  In principle (that is, principles of physics), timing and intensity adjustments should trade off in a simple way, such that half the duration equals half the intensity (of log intensity, if you want to get technical), which equals half the dose.  In practice, physiology intervenes, and the tradeoff is not so neat.  Since 25 minutes is hardly the longest duration patients use – even 60 minutes is not that rare – further cutting duration is the not most efficient way to taper down. By contrast, 10,000 lux is the maximum intensity of white light that has been investigated by clinical researchers, so it makes more intuitive sense to begin by cutting the intensity.

If you are using one of the Daylight Classic models, you can try switching on the “low” instead of the “high” level. This step will provide approximately 7,500 lux, a significant jump downward while remaining clearly in the therapeutic range.  If the anxiety does not lessen after three days at 7,500 lux, move your chair back a few inches. You will then be in the 5,000 lux range, which we know is still an effective level.  If both those changes make no difference, it’s time to cut the duration, sitting about 16 inches from the screen with the intensity remaining at “low.” Try a 20 minute session, and then, if necessary a 15 minute session.  By then, you’d be getting a fraction of the dose you are currently experiencing, and there is a good chance the anxiety will abate while the antidepressant effect remains.  It is possible that some people will remain as anxious as ever while trying these dose reductions.  If you’re one of them, you may face the difficult decision of continuing light therapy but remaining anxious, or giving up on light therapy and turning elsewhere for symptom relief.  Best of luck in this exploration!

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If I do not know how many minutes it takes me to fall asleep, should I err on the side of allowing more or less time to fall asleep? For example, I want to wake up at 5 AM. It takes me between 10 and 40 minutes to fall asleep.  Should I go to bed at 9:20 PM or 8:50 PM if I want to fall asleep at 9:30 PM? I read in bed until I nod off, then I turn off the side lamp.

Your target of achieving 7.5 hours of sleep is excellent, and in line with most studies that suggest we should obtain 7-9 hours of sleep per night. It is always better to allow additional time to fall asleep. Thus, you should go to bed at 8:50 PM. If you fall asleep faster (before 40 minutes), you will obtain a little more sleep, which will be beneficial.

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My two year old goes to sleep between 7 and 7:30 pm, and often wakes up before 5 am. He usually takes a 2 hour nap. If he naps for less than 2 hours, we try for an earlier bedtime. Staying up later or going to bed earlier does not change his wake-up time. We have blackout shades plus blackout curtains in his room. He gets no illumination from sun at dawn, and after waking up he only gets artificial light because it’s still dark outside until about 7 am now. His pattern didn’t differ in the summer. I am following the standard advice such as putting him to bed while drowsy but still awake, but he still usually wakes before 5 am. Can any of the techniques on this website be useful for helping a toddler with early wakening?

It’s relatively difficult to answer such a question without knowing the patient, for example, the temperamental characteristics of the patient. It sounds as if he might be a morning type, which occurs frequently in toddlerhood, especially in children born preterm. I would suggest avoiding later diurnal naps, and trying to consolidate the nap, for example, between 1 and 2 pm. The parents can enrich the diet with nutrients rich in tryptophan, which is useful for sleep continuity.

At this moment I would not consider pharmacological treatment because we speak about a chronotype which can vary with age, and no diurnal consequences are reported about possible sleep restriction.

Eleven hours of sleep a day could be sufficient, following recently published recommendations from American Academy of Sleep Medicine (AASM) and the National Sleep Foundation.

More information on the AASM recommendations for pediatric populations is available here; more information on tryptophan is available here and here.

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Can prolonged use of a light box cause eye sensitivity and headaches? I used a light box for about two years and developed these problems.

The answer is: not that we know of.  The symptoms you describe can certainly occur as short-term side effects, occurring during the use of a light box.   But there is no evidence of cumulative, prolonged or delayed ocular and/or headache effects from ordinary bright light therapy usage.  The combination of light sensitivity and light-aggravated headaches points in the possible direction of a migraine disorder.  We suggest consulting a neurologist.

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I’ve been using light therapy for SAD for about a month and have found it tremendously helpful for my mood. I suffered with SAD for about 6 months out of the year during winter for the past six years and just recently read Winter Blues by Rosenthal and realized that the 30 min I had stuck to for light therapy probably hadn’t been enough. I now do about an hour right when I wake up, and about an hour later sometime before 2 or 3 PM. Lately my body has been waking up between 4:30 (yikes!) and 5:45, which has not been great for me. I have shifted my bedtime earlier and I fall right asleep, but am tired of waking up so early and not being able to fall back asleep- and, I am okay with bed at 9:30 or 10, but don’t want to sleep earlier because then I miss so much of my evening, but since my body wakes me up so early, I am seriously exhausted by 8 PM. I’m 28 years old, active, and by 8 PM I feel like I’m 90 years old!!! Is there any way to alter my light therapy so that I can sleep in later? Try less or at a different time? Thanks for your help!

You are making a big mistake with self-treatment.  See Dr. Terman’s book, Reset Your Inner Clock, for a detailed explanation of setting light therapy parameters: duration of the session, timing of the session relative to your circadian (“inner”) clock, intensity of the light, sitting distance from the light box screen, and spectral quality (amount of blue in the white color mixture).  In a nutshell, you almost certainly have given yourself a light overdose by doubling the duration of exposure upon wake-up.  If 30 minute sessions were inadequate – which implies persistent, residual symptoms of depression – you might increase exposure duration in a series of small steps (such as 5 minutes), testing each step for three or four days before increasing it further.  A 60 minute exposure at 10,000 lux is virtually the maximum used in clinical practice, most often for patients who have not responded at all to shorter durations.  A major effect of such overdose is a large shift in the circadian clock to an earlier hour, resulting in premature awakening and evening sleepiness – just as you describe.  Adding another hour of light exposure later in the day is almost surely also excessive.  If you are slumping in the afternoon, a relatively short supplementary session – such as 10 or 15 minutes – is sufficient for most people to truncate the slump.

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How do I know if I am sensitive to the UV lights particularly with my eyes? I do not have any eye disorders, but I know I’m just a more sensitive person in general. Are there any eye or skin tests I could take before using the light therapy so I do not burn or damage my eyes or skin?

That’s a really good question!  Many people worry about the eye safety of bright light therapy. You are absolutely correct to be concerned about UV light.  Light from this non-visible part of the spectrum can cause a variety of ocular problems, especially cataracts. The good news is that most, legitimate light boxes include a diffuser screen that is designed to entirely block out this wavelength portion. This is another good reason to only use light boxes that have been clinically tested, both for effectiveness and safety.

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Dr. Terman, I have read with great interest the summaries of your research, and some of your blog postings. I am wondering if you have ever come across patients whose sleep time and wake time are incredibly reliable, who don’t have a mood disorder, but who have an abnormally low afternoon dip? I have long had this problem — no issues with falling asleep, staying asleep, or waking up, but a dip after lunch that is so severe that I find myself walking across the street with my eyes closed. I am as perky as can be in the morning, but it is the most uncomfortable fight to try to stay awake in the afternoon. Nothing I have ever tried, other than an actual prescription stimulant, has had any effect, and I don’t like how I feel on the stimulant. I recently traveled to Israel, where I thought I’d be incredibly jet lagged, but, surprisingly, I felt far better than at home in the DC area. The only things I could think of were that it was so incredibly blindingly bright all day long every day, or that the time of my afternoon dip would literally have been while I was asleep because of the time change, and that my rhythms didn’t adjust in the week that I was there. I purchased a light box on the advice of my doctor, but I can’t find any information on how I should use it. I’m wondering if you’ve ever met anyone like me? It would be the greatest gift if I could have my afternoons, and not have to plan my days around needing a nap. Doctors have long told me that it’s healthy to take a nap, but it’s one thing to decide to take one, and it’s another to absolutely require one.

You had the correct insight.  The afternoon slump can occur with or without depression. If you measure the interval between the slump and the midpoint of nighttime sleep, they’re about 12 hours apart. (This is separate from the “post-prandial” slump some people experience after a heavy midday meal.)  You don’t need to spend all day in “blinding bright light” to counteract the slump.  The principle is to get to the light box as soon as you sense the onset of the slump, and not wait until it gets severe.  This can nip the slump in the bud, even with 10,000 lux light exposure as short as 10 minutes.  Some people will need longer, so you’ll need to experiment.  There are days when the slump comes a bit earlier or later, so don’t set the light session by the clock.  Rather, be attentive to the onset of the slump.  This technique works for many people, but not for everyone.  If it fails, and you have control of your work space, raising ambient light level in the afternoon to about 2000 lux – from ceiling or desk fixtures – including the light box – is another approach.  Don’t overdo it, however, or you may experience jitteriness, headache, eyestrain, or sudden mood shifts that interfere with work.

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How do I know if I am sensitive to the UV lights particularly with my eyes? I do not have any eye disorders, but I know I’m just a more sensitive person in general. Are there any eye or skin tests I could take before using the light therapy so I do not burn or damage my eyes or skin?

That’s a really good question!  Many people worry about the eye safety of bright light therapy.

You are absolutely correct to be concerned about UV light.  Light from this non-visible part of the spectrum can cause a variety of eye problems, especially macular degeneration.

The good news is that most, legitimate light boxes include a diffuser screen that is designed to entirely block out this portion of the wavelength.  This is another good reason to only use light boxes that have been clinically tested, both for effectiveness and safety.

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I have been using my light box for 30 minutes per day for 3 days in the morning and have noticed an increase in baseline anxiety. If i have baseline anxiety that seemed worse in the winter, is light therapy recommended or contraindicated?  I don’t have any history of hypomania. Should I stick it out for 2 more weeks and see if it resolves? Or do you recommend decreasing duration in front of lights to 15 minutes per day? At what point is light therapy contraindicated?

Another really good question.  First off, we want to emphasize a general point about clinical questions of this kind:  specific therapy  recommendations for a given individual in a given situation should come from one’s doctor and the ongoing treatment process.  As an educational website, our job is to provide general information about chronotherapy to the public.   The responses we provide are thus general, educational ones and should not be taken as clinical recommendations.  With that caveat, let me share some thoughts about this type of situation.
First, baseline anxiety is something that I pay a great deal of attention to as a clinician when I am considering any antidepressant treatment.  There is data that suggests that when depression is mixed with anxiety symptoms, the rate of antidepressant-induced manic response is heightened.  Even when there’s no past history of manic symptoms, antidepressants can sometimes activate and reveal underlying bipolar dispositions that were not evident.  Apart from the risk of treatment-induced mania, bright light therapy can cause or worsen ordinary (ie, not related to mania or bipolar disorder) anxiety as a side effect.
Second, I wasn’t clear about the nature of the diagnostic problem for which bright light therapy is being used here:  were you using light therapy for seasonal anxiety, for depression, for depression mixed with anxiety?  This would also have a bearing on how to manage your response to bright light therapy.
As a general rule, if someone that I am treating with bright light therapy experiences an increase in their anxiety, I would move to reduce and/or consider discontinuing the treatment.  The good news is that bright light therapy can be quickly and incrementally adjusted in several ways:  many light therapy lamps have a low and high lux option that allow for switching to a lower light intensity setting; the duration of exposure can be reduced; the distance from the light box can be increased; last, some studies suggest that light delivered later in the day, towards midday, causes less anxiety than early morning light.  So there are several, easy tweaks that can be done to reduce bright light therapy-induced anxiety.   The easy and rapid adjustability of treatments is a distinct characteristic and advantage of most chronotherapies.

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How many hours should we sleep at night?

It depends on the individual. Six hours is around the short extreme, and nine hours is around the long extreme.  Most people fall somewhere in the middle.  How can you tell what’s right for you?  One clue is whether you feel work or family pressures are preventing you from going to bed, or staying in bed, when you’re sleepy.  The best measure, though, is if you feel alert throughout the day, stay in a reasonably good mood, and don’t oversleep on days off.  If you don’t do all three of these things, you should test whether a longer sleep interval — daily throughout the week — does the trick.  On the other end, some people allow themselves to sleep longer than they need, and they pay for this with low mood and fatigue during the day.  They often say to themselves, “If I could only sleep longer, I would have more energy the next day.” That may be a reasonable intuition, but it is a mistake.  Longer sleep than necessary can feed depression and a sense of exhaustion.

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I am a teacher, so I have to go to work early in the morning. I use a dawn simulator, and a light box, for 20 minutes in the morning when I first wake up. This maintains my ability to get up early and feel energetic during the day. However, because my job is demanding, I would like to sleep a few extra hours on the weekends. From experience, napping in the afternoon is a mistake as I feel groggy. Also, I know missing my regular wake up time is a big mistake. I would like to get up and do my regular light time, and then go back to sleep for a few hours. Would this seriously disturb my overall sleep pattern? I want the extra sleep but not at the expense of my mental wellbeing.

In general, it is best to maintain a regular bedtime, and wake up time, even on the weekends, to ensure you remain in sync with the environment. In your situation, however, we recommend a short nap of 30 minutes during the day: this restricted duration is restorative, yet produces minimal grogginess (“sleep inertia”) when you wake up.  Set your cellphone timer to alert you to get up, and don’t nap once evening approaches. If you do feel groggy after the nap, you could drink a caffeinated beverage immediately upon awakening.

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I have decided to stop using the light and have not used it for 4-5 days now. I am still waking up at 5 AM instead of 6 AM and feeling unrested. How long do you think it will take before I am waking up at my normal time?

Early waking under light therapy is a side effect of light overdose, caused by one or more of the following factors: light too intense, session duration too long, or session scheduling too early in the morning. Dose adjustments almost always resolve the problem, but may require clinical supervision. Circadian rhythms usually readjust quickly to the one-hour phase advance you report — this is akin to one-hour jet lag adjustment (as you might experience flying from New York to Chicago) or the transient everyone experiences during switch from Standard Time to Daylight Saving Time. The rate of adjustment will of course vary from individual to individual. You can expedite the process by staying in dim light after you wake up, and using strong sunglasses when outdoors during morning hours

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I used a light box for about 10 days, and ended up experiencing anxiety and irritability, even after cutting back on the time of exposure (from 20 to 10 minutes), and increasing the distance between my eyes and the light box by 6 and 12 inches. Does this mean I am just one of those people who cannot use a light box?

You may be correct that your anxiety is a side effect of light exposure. But not necessarily. Do you get equally anxious when outdoors in sunlight? It seems that you should be working under clinical supervision, not self-treating. There are too many possible factors that might interact, and a Q&A forum such as this is not the place to do it. One possibility is that you are reacting specifically to the far-blue component of light from the box. If so, you could try screening it out with wrap-around blue-blocking lenses which maximize transmission of longer wavelengths (see 65% model at If your anxiety persists, you should abstain from light therapy and seek an alternate treatment.

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Does time of day matter when undergoing surgery? I realize that a patient is at the mercy of the hospital scheduler, but as a night person, would I do better to opt for morning or afternoon? Or is the circadian rhythm of the surgeon a more important determinant? After all, he should be at his peak of energy and alertness when he operates.

Very provactive questions, with no easy answer. Consider also that there are daily rhythms of sensitivity to anesthetics and pain tolerance, which are not necessarily in synch with your behavioral tendency toward eveningness. There may well be times of day when you could achieve full anesthetic effect at far lower dose, and with shorter stay in the recovery room. The best place to read about these possibilities is in The Body Clock Guide to Better Health, listed at the top of the Recommended General Reading list at //

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If one is sensitive to some fluorescent light — for example, I get migraines — can light boxes be used to treat SAD?

Adverse reactions to fluorescent lighting is usually due to poorly designed lighting installations with a high glare factor, or electronic ballasting of low, 60-Hz frequency. Most likely, you would not experience such headaches using a well-designed light box with a smooth diffusion screen and high-frequency ballasting. Headache (though not migraines) is fairly frequently reported as a side effect during the first few days of light therapy, but the problem usually resolves quickly. If not, reducing light dose — for example, with shorter treatment sessions — often provides relief. Extremely few users have experienced long-term, intractable headache under light therapy.

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I notice that the CET Store is now offering a 7500 lux light box for the general public as well as a professional model with the standard 10,000 lux. Is 7500 lux really enough? Will it significantly increase the length of time I need to sit in front of it? Is the research leaning towards the conclusion that 10,000 lux might be overkill?

7,500 lux is definitely within the active therapeutic range. Two recent studies using CET’s new unit were not with SAD patients, however. In those studies, patients with non-seasonal chronic depression or antepartum depression (depression during pregnancy) used the unit for 45 minutes to one hour. In a new study, patients with non-seasonal bipolar disorder are using the unit for 30 minutes or less. We do not yet know the general timing requirements, which will surely vary widely among individuals. It stands to reason that, on average, 7,500 lux-users will need somewhat longer exposure. 10,000 lux is not overkill, unless it is used in longer sessions than are necessary.

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Do you consider seasonal and non-seasonal depressions to be separate entities, or are they opposite ends of a single spectrum? I seem to be right in the middle — or have both — if such is possible. In winter I become deeply depressed, while in summer the depression gets milder but does not completely remit — I certainly do not get the euphoria or “up” typical of SAD. I crave light year-round, though much more in winter. I have tried using a light box year round. In winter it takes me from -7 to about -2. In summer it moves me from about -3 to -1. But, the only time I get above 0 is if I go camping in sunny weather for several days. Similarly, I have had only moderate success with antidepressants. Am I alone?

SAD and Chronic Depression Benefit from Light Therapy

Certainly you are not alone. Many people with chronic depression find that it is seasonally modulated with winters worse. A recent clinical trial of light therapy for chronic depression, given at all times of year, found that the response rate is similar to that for SAD in winter. Patients with SAD often report that light therapy greatly improves their depression, but not up to their normal spring/summer experience. (By the way, although some SAD patients feel euphoric in spring, that is not typical; most feel calm, or just “normal.”)

When the Response to Light Therapy is Inadequate

If there is only partial response to light therapy, the daily light dose – i.e. exposure duration or intensity — may have been inadequate. Alternatively, as you suggest, a given individual may not be able to attain full response. Light therapy can be used with antidepressant medications. Sometimes that improves response relative to either one alone. Used in combination, the optimum drug dose can sometimes be lower than when the drug is used alone.

Another Alternative: Light Plus Negative Air Ions

Another potential combination is light plus negative air ionization, but this has never been formally tested in clinical trials. If that is what you decide to try, we strongly advise not using the light box and ionizer simultaneously, because there may be electrical interactions that blunt the ion dose.

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Is there any kind of device I could use to see how much light comes off my light box at 24 inches? I am using an old one that a friend dug out of her attic, and the manufacturer does not respond to my inquiries.

Not easy. There is an industrial unit, called a photometer, which reads illumination in lux. Probably quite expensive, although some photo stores have them and might lend or rent one to you for a few days. If you do this, make sure that the sensor is a rounded, “cosine-corrected” probe, rather than a directional probe. The latter will inflate lux readings.

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I recently took your very interesting and informative on-line questionnaires. The feedback was that I probably have a mild to moderate depression with strong seasonal tendencies. Any suggestions how to approach working with this?

As far as we know, the optimum light treatment regimen for subsyndromal seasonal affective disorder (SAD), or winter doldrums, is no different from that for full-blown SAD. In other words, milder winter depression does not imply that you need less light than for major depression. Therefore, for starters, we would suggest that you follow the 30-minute, 10,000 lux regimen described on our website.

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We greatly appreciate your feedback — this kind of news is what keeps us going! Patients with non-seasonal depression, or depression that lifts somewhat but incompletely in summer, are now using light therapy throughout the year. This is unnecessary (and not recommended) for those with “simple SAD” who are asymptomatic in late spring and throughout the summer. You can easily test whether continuing year-round would be valuable for you personally: come early May, skip the lights for one or more days; if you slump, resume the lights for two weeks and then try skipping again. If you don’t slump, just wait until you have the first inklings of fall/winter recurrence, then go back to your proven light therapy routine. Assuming that you need summer treatment, we recommend testing whether an early morning walk outdoors (whether just a stroll, a power walk or a jog) would do the trick. Finally, some patients find that they can reduce light dose after the worst of the winter passes, by shortening treatment session duration.

[FORUM PARTICIPANTS AND VISITORS: If you have found our information and advice useful, please help us help others, and make a tax-deductible contribution to CET. For info, click the DONATE button on our home page. All thanks, The CET Board.]

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Can you tell me if someone who has had one of the following treatments, and was advised not to be exposed to sunlight, might still undergo light therapy? Microdermabrasion, Chemical Peel, Laser Hair Removal or Intense Pulsed Light Photo-rejuvenation. Thank you.

When doctors advise patients to avoid sunlight, the risk factor is almost always ultraviolet (UV) radiation. As you can see from, an adequate light box should screen out UV, in which case there should be no UV risk. However, some light boxes screen out more UV than others, and boxes that use full-spectrum light bulbs present an additional challenge for adequate filtering. As a result, we can still see skin reddening and puffiness under filtered full-spectrum light, which is not good. CET recommends a light box with a polycarbonate diffusing screen and a lower color temperature (4000 Kelvin) than used in full spectrum boxes (5500 Kelvin and above). Unless your dermatologist wants you to avoid blue light as well as UV, this apparatus should suit your need.

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WE HAVE RE-WRITTEN THE FOLLOWING QUESTION TO GENERALIZE IT FOR THIS FORUM: I use the drug Tegretol (carbamazepine) — a tricyclic anticonvulsant drug also used to control mania in bipolar disorder — along with a 50-sunscreen and light therapy. I’ve noticed splotchy, reddening skin, especially after completing light therapy sessions. Is use of the lights dangerous for me?

As early as 1990, we published a warning in the journal Photochemistry and Photobiology (vol. 51, pp. 781-792) that the use of tricyclic drugs can result in photosensitizing reactions in the presence of both ultraviolet light (UV below 400 nm) and visible light (up to about 550 nm, including the blue and green ranges). Such photosensitization could affect both skin and eye structures. Sunscreen would not protect your skin from light energy in the visible range, and obviously it would not protect your eyes in either UV or visible ranges. Although the manufacturer does not specifically list Tegretol as a photosensitizer, they do list side effects of both skin reactions and depression.

We do not know the specifics of your case — there could be various reasons for the skin reactions you report. Obviously, you should immediately test whether the reactions disappear when you stop using your light box, and whether the problem extends to outdoor sunlight exposure. You should promptly consult your dermatologist; receive a thorough ophthalmic exam (including slit-lamp fundoscopy and tonometry); and see your psychiatrist to review your drug dose, plasma level of the drug and blood chemistry screen, and consider other possible drug-drug interactions and alternate mood stabilizers.

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In answer to another person’s question, you said, “Waking up to bright morning light, whether from outdoors or timed artificial light sources, is far healthier than waking in a dark bedroom.” Can you explain why this is true? I usually go to bed between 11:00 pm and midnight. I set my alarm for 9:00 am and get up sometime before 10:00 am. I put blackout shades in the bedroom because during the summer the sun was waking me up at about 6:00 am, which meant I was getting only 6-7 hours of sleep. (I think I need about 8-9 hours). However, with the blackout shades, I find it hard to wake up, and when I do I feel sleepy rather than refreshed. I suspect that my sleep habits may be negatively affecting my mild depression and mild winter blues. Do you have any suggestions? If I want to change my sleep schedule so that I am waking up earlier, what increments of change would you recommend?

This is a meaty, intelligent question! Our body clock, which modulates sleep and wakefulness, relies on daily early-morning light exposure to stay in sync with the external world. Without appropriately timed exposure, the clock is vulnerable to drifting later and later — and telling our brain to wake up later than we might desire. Grogginess and depressed mood commonly accompany this “delay shift.” You complain about the very early sunrise in summer, which causes you to wake earlier than you want. On the other hand, your blackout shades are triggering a bothersome delay shift. Short of moving southward, where the sun rises later in summer, the only obvious solution is technical: timed artificial dawn simulation in your bedroom, with the shades drawn. See’s section on dawn simulation, and the description of apparatus at the CET Store. Simply forcing yourself to wake up earlier in a dark bedroom is no solution, because your sleep will then get out of sync with your clock, and you will lose the refreshing benefit of an optimum night in bed.

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In dawn/dusk simulation therapy, how important is the dusk simulation part? Also, can dusk simulation be successful even if used at different times in the evening?

Formal clinical trials have concentrated on dawn simulation, without the dusk simulation. Dawn is effective on its own. Clinical case studies suggest, however, that addition of the dusk signal at bedtime can be very helpful for people who have trouble falling asleep. Subjectively, it has a soporific quality, not unlike the sensation one gets when taking a low-dose, short-acting sleeping pill. When the dusk signal was added, some patients immediately fell asleep up to two hours earlier than usual. There are no studies or cases to report that used dusk simulation on its own, without the dawn signal. Possibly this would be useful as a soporific for people, with insomnia at bedtime, who have no problem with spontaneous rising in the morning. As for optimum timing of the dusk signal, case studies suggest that beginning the fade 20 minutes before desired sleep onset is effective. Of course, you have to be in bed to observe the fading light. . . .

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What is the impact of SAD on hormone levels, especially estrogens, prolactin, testosterone and luteinizing hormone? Is it possible that SAD reduces their levels? Could the combination of light therapy and hormones be a more effective treatment than combination with antidepressants?

The effect of SAD on hormone levels is not clear and would benefit from further study. We know of no studies examining SAD effects on estrogens or testosterone. At least two studies suggest that people with SAD do have low prolactin, but another does not. The combination of light therapy with hormones is an intriguing idea, but has never been tested for safety or efficacy.

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Is there any report of hypomanic episodes with negative air ion therapy?

In formal clinical trials, when side effects were measured, there were no indication of hypomanic episodes. However, clinical cases include a small number of users who have become “wired” (or hypomanic) with negative air ion overdose — when, for example, they leave the ionizer on all night. It is safest to use the method as has been investigated: for 30 minutes after waking or 90 minutes before waking (automatically switched on and off by an electronic timer).

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Blue vs. White Light: Mixed Results

First, there have been no published clinical trials showing that blue light is specifically antidepressant. On the other hand, there have been several basic research studies showing that by restricting light to the short-wavelength blue region, circadian rhythm resetting and melatonin hormone suppression can be achieved with lower total light energy than when using white light. Light wavelengths outside the blue region also trigger the circadian system and suppress melatonin, however. Indeed, by definition, white light contains blue. The balance of blue with other wavelengths in white light has repeatedly been demonstrated to be safe, effective and visually comfortable.

Blue Light Warnings

Blue light sources, especially when they are small, can cause extreme aversive glare. When they are placed near the eyes, as the vendor recommends, they can be intolerable. When placed at a “comfortable” distance, the eye does not receive the full-field illumination that is optimal for antidepressant treatment. There are also unresolved issues of safety. Blue light – like ultraviolet light – can cause a photosensitizing reaction in combination with several prescription drugs, thus harming the retina. The hazard of repeated exposure to blue light in therapeutic combinations is still a matter for investigation. In our opinion, it is premature, irresponsible and exploitative at this point to market blue light devices to people suffering depressive illness.

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My 12-year-old son was diagnosed with SAD when he was about eight. He has suffered since he was six, if not younger. I have been looking for information on the long-term prognosis for children with SAD. Do you know of any studies done? Is it the same as for other types of depressive illness?

Unfortunately, there have been no long-term studies of childhood SAD. We would guess that once it emerges, the seasonal pattern remains, and one does not “grow out of it.” Some children and teens have used bright light therapy, dawn simulation therapy, or both with benefit. Managing compliance with bright light therapy has been a problem. Some children — in our experience, pubescent boys — have shown pronounced side effects of flushing, rapid heartbeat and agitation upon initiation of bright light therapy. Therefore, if tried, a doctor’s supervision and monitoring are important.

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I understand that only a small percentage of the population exhibits symptoms clinically significant enough to be diagnosed as being seasonal affective disorder (SAD). However, to what extent would you expect SAD-like symptoms to affect the rest of the population? In northern latitudes, does it appear that the majority show changes in mood and behavior similar but not as severe as those for SAD?

The number of people with “winter doldrums” or subsyndromal SAD is at least three times higher than the number with full-fledged SAD. The difference between the two groups is subtle, not obvious. Doldrums sufferers experience the same range of winter symptoms, including depressed mood, but short of a major depressive episode. Broadly speaking, they can plow through winter with effort without becoming overwhelmed and seriously dysfunctional. The months of symptom onset and springtime remission are the same as for SAD. Doldrums sufferers also respond well to light therapy, and usually they need the same lighting regimen as for SAD: the same light intensity, exposure duration and time of day of treatment. CET helps people differentiate SAD from subsyndromal SAD in its Automated Personalized Inventory for Depression and SAD (AutoPIDS at, and offers personalized start-up guidelines for treatment in its Automated Morningness-Eveningness Questionnaire (AutoMEQ). We do not believe that a majority of people show subsyndromal SAD; the proportion is probably closer to 30% in middle-to-northern latitudes of the U.S. and southern Canada.

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Would light therapy be effective for a person who is totally blind? Some people with blindness seem to have mood swings with the seasons. Perhaps they react differently — to the warmth of the sun rather than the sight of sunshine.

The sight of sunshine, in fact, has little or nothing to do with the mood-regulating effect of light. Almost certainly, the effect is mediated by nerve fibers that travel from the retina of the eye into the brain area that controls the body’s circadian rhythms — the suprachiastmatic nuclei of the hypothalamus. Other neurons from the retina independently project to visual sensory areas of the brain. One can be totally blind to visual sensation while still processing light signals in the suprachiastmatic nuclei, and in such cases we would expect the seasonal effect (and response to light therapy) to be similar to that of sighted people. There have been studies showing that light can affect melatonin production by the pineal gland — which is also mediated by the suprachiastmatic nuclei — in people who lack all visual sensory perception. If that effect were similar in blind people with bilateral ocular enucleation (removal of the eyeballs because of swelling, pain or other pathology), this interpretation would have to be modified. . . .

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I use my light box for about 30 minutes each morning. However, I’ve been thinking about ways to brighten up my rooms all day. I find that I’m much more cheery if the room where I’m working is bathed in bright, warm light. Given that I shouldn’t leave my 10,000 lux light on all day and given that you recommend against full-spectrum lighting, what might be my best options for bathing my rooms with light?

The lux level received from a light box strictly depends on your distance from the source. There would be no problem leaving your light box switched on during the day if you are not physically close to it. By remaining outside the active therapeutic range (for example, more than 3 feet using the Daylight 10,000 lux Clinical Model we recommend) you can continue to enjoy the enhanced ambient room illumination. For brightening other rooms without the light box, we recommend diffuse or indirect illumination from standard incandescent (including halogen) lamps or fluorescent lamps rated 3000-4000 Kelvin color temperature. In general, the lower the color temperature, the “warmer” (less blue, more pinkish) the hue. As you suggest, for long-term comfort it makes sense to avoid specialized fluorescent or incandescent lamps with higher color temperature, which exacerbates glare.

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I used my light box at 8 a.m. during daylight savings time. Now that we’re back on standard time, should I use it at 7 a.m., since that’s when the light would still be the same in relation to the biological clock?

When shifting from daylight savings to standard time, we need to give the biological clock an opportunity to shift also. Think about it as a jet-lag adjustment — you want to resynchronize to the new time zone. Rather than resisting the change — in your example, by using the lights at 7 a.m. rather than 8 a.m. — you should accelerate the readjustment. One approach is to skip light therapy on Sunday morning after the time change, allowing your internal clock to drift later (ideally, by an hour). On Monday morning, you resume at 8 a.m. standard time. Most people achieve this adjustment effortlessly, but some experience distinct jet-lag-type symptoms that can last up to several days.

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I would like to know what to do about my severely advanced circadian rhythm!

Here are some strategies: (1) Keep your room lights bright all evening before you go to sleep. (2) Use bright light therapy an hour before you go to sleep, and edge it later as you start sleeping later. (3) Keep your shades drawn to avoid dawn and early daylight exposure. (4) Try the lowest possible dose of immediate-release melatonin (0.1 mg) as soon as you wake up, but be sure not to go into bright light, including outdoor light, for at least two hours. (5) Wear dark sunglasses whenever outdoors in the morning. An alternative, for better visibility, would be 4% dark-orange wrap-around’s from Readers may notice that these strategies are generally opposite to those used to counteract the more common delayed sleep phase syndrome. They are also opposite to the general strategy for treating depression. Any of these strategies may work on their own, but in all likelihood you’ll need to find an effective combination.

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Although these applications have not been studied as extensively as light therapy for SAD, all indications are Yes. Clinical trials have been completed showing benefit of light therapy to non-seasonal recurrent, chronic, bipolar and even rapid cycling depression. We are not yet sure whether the same “early morning light prescription” as is used for SAD will prove optimal for non-seasonal depression. However, the most recent trials show clear benefit of morning light compared to placebo. In cases of bipolar and rapid cycling depression — variants of “manic depression” — light therapy should not be attempted without using a mood stabilizing drug, because of the risk of a sudden switch to the disruptive “high” state. This clearly implies that the treatment must be done under professional guidance and supervision.

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It is very difficult to respond to such a dense set of questions in q&a format, but we’ll give it a try. 1. For winter depression, one can try discontinuing treatment at the time of year remission has previously occurred. This differs greatly among individuals. On average, SAD patients like to continue treatment until the end of April in order to avoid risk of relapse. If you slump when you discontinue, you can always start up again for a few more weeks. 2. Just stop. 3. There should be no need to adjust timing as the season changes. 4. If you are using light therapy for year-round depression, you need to experiment with varying the light dose. If you find yourself “too high” come spring and summer, reduce exposure duration to see if you calm down without losing the benefit. 5. Some people respond selectively to light or negative ions, while some respond to both. (And some to neither!) Current clinical trials at Columbia and Wesleyan indicate that both light and ion treatments are effective for year-round depression, as compared with a placebo control.

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About five days ago, I increased the amount of time in front of my light box from 30 to 45 minutes, to try to stave off the mid-afternoon slump. It is working more or less, but I think I am now experiencing what you termed “irritable hypomania.” I am definitely more irritable, and I spend much of the day feeling like I am in overdrive. Any suggestions?

Yes, you are experiencing morning-light overdose, and should immediately fall back to 30 minutes. An alternate tactic to avoid afternoon slumping is a relatively short supplementary exposure — usually, 10 minutes is sufficient — just as you begin to feel the slump set in. You need not schedule this p.m. exposure precisely (as is important for morning light). Rather, use it when you feel you need it. If you are at work, without your light box, consider getting the new work station lamp (DaylightXL) described at It is relatively inexpensive, but does this kind of job well

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Do you have any info on the small, hand-held lighting devices that have recently been marketed? How do they compare with the 10,000 lux lamps that have been so successful?

There are two kinds of possible comparisons. One is with an ineffective placebo condition (such as dim light outside the therapeutic range, or a negative air ion generator that has been deactivated). Another type of comparison can be made with established treatments, such as 10,000 lux light therapy or antidepressant meds. We have to await completion of adequate controlled clinical trials before making any conclusion about the efficacy of hand-held devices, which greatly restrict the field of illumination.

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Will longer exposure to a dimmer light box (say, 7500 lux) accomplish the same effect as 30 minutes at 10,000 lux?

The answer is probably yes, although how much longer is not clear. There has been no direct, systematic research on this question, although we know that light boxes providing 2500 to 10,000 lux can be fully effective given sufficient exposure duration. The required duration at any dose level is determined in part by the individual’s own sensitivity to the light. For example, even with 10,000 lux, one person may need only 20 minutes of exposure, while another needs 30 minutes or even 60 minutes. In early clinical trials of 2500 lux, the typical duration was 2 hours and above. One trial with 7000 lux settled on 1 hour exposures for all patients, although that may have been too long in some cases.

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Regardless of the season, on rainy and cloudy days I feel so depressed that I often find life too hard to live. And on a bright winter day I can feel fine. If I do not have SAD, then what is the name of my “light-deprivation-oriented” depression, and how can I treat it?

You have given it a good name! Even patients with SAD show a similar reaction of mood and energy slumps on rainy and cloudy days in the summer. And you might take a hint from them: they will pull their light boxes out of the closet, a day at a time, to counteract such transient dips.

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Jet Lag/High Latitudes=Mood Swings

Mood swings — upward or downward — are often seen in extreme cases of jet lag. Additionally, irritable hypomania — as you appear to report when in Alaska — is common during long summer days at high latitudes. The internal circadian clock can quickly drift away from the local time standard when the sun is up nearly 24 hours in summer (and also when it is down nearly 24 hours in winter at the same latitudes). Upon sudden return to “normal” day-night conditions, readjustment can be arduous. It is impossible to say whether your winter depressions in recent years might have been triggered by your difficult early travel experience. It is interesting to note that the very first SAD patient diagnosed and treated at the National Institute of Mental Health lost seasonality and became chronically depressed for two years when he returned to the States from an extended vacation in Australia.

Avoid Extreme Jet Lag/Latitude Differences

Obviously, jet lag — or sudden switches between locations with greatly different day-night cycles — can have long-term consequences for mood regulation in vulnerable people. Your occasional winter depressions might well respond to standard bright light therapy, as described on Research is currently active in devising artificial light-dark schedules and medication regimens to forestall or attenuate jet lag, but as of yet there is no clear prescription (despite the claims of unscrupulous lighting manufacturers on the Web). We would advise avoiding the kind of “extreme” travel you describe, and choosing instead destinations in a similar latitude range and within a 6-hour time zone difference of your home area.

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If someone else is in the room while I am having my light therapy, will it throw off their system?

Probably not, unless you are switching on the lights in your bedroom, while your partner is still trying to sleep.

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I am getting some success against depression with a light box, but still find that I crave light, especially by the afternoon. My mood also tends to drop around then (3:00ish). Does this indicate I should use the light box longer in the morning? Would it help to use it again in the afternoon? Can I use the box, without sitting right in front of it, for general lighting, just to get more brightness in here?

Smart questions! Response in three parts: (1) Often, the afternoon slump vanishes when the morning light dose is increased — so, yes, give that a try. (2) Some patients find that they can largely prevent the afternoon slump with a supplementary light therapy session as soon as they feel the slump setting in. Often, a very brief session — for example, 10-15 minutes — suffices. Unlike morning light therapy, which should be repeated consistently every day, the supplementary session can be done “PRN” — as you need it. If there is a day without slumping, you can skip the session. If the slump starts at different times from day to day — say, 2:00 p.m. on one day, 3:30 p.m. on another — you can vary the time of afternoon light exposure. And if you are out of the house when the slump hits, you do not have to feel guilty about missing the session. (3) No problem with leaving the light box on for extended periods during the day, as long as you are not sitting in direct proximity, risking overdose.

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About Question #1561: What does happen if you use light too early? Once in a while? Regularly?

Light Exposure & Circadian Clock Resetting

A primary effect of light exposure throughout the night and early morning is to reset the internal circadian clock. The aim of light therapy for depression is to reset the clock earlier in order to counteract dark morning bedroom conditions (especially in winter). When light is presented during most of the night, the clock resets later, not earlier. About two hours before wake-up — this is just an average; the timing might differ — body temperature reaches its nightly minimum and the pineal gland stops secreting melatonin. Thereafter, light presentation resets the clock earlier, which is what we want. The switchover from later to earlier clock resetting can happen quite quickly, so we try to avoid premature light exposure, which would work opposite to the desired effect by resetting the clock later.

Early Light Exposure Can Bee Disruptive

Such early exposure even on a single day can be disruptive, and induce a jet-lag-type effect. That is why it makes most sense to skip light treatment on the occasional day you have to be out of the house very early. If you were to use the light too early every day — as your question asks — there are two possible outcomes, depending on whether you happen to “hit” the circadian clock in its delaying or advancing state. On the one hand, you might find it difficult to stay awake, or to become alert till hours later. On the other hand, you might start waking up far earlier than desired. We want to avoid either of those outcomes.

[FORUM PARTICIPANTS AND VISITORS: If you have found our information and advice useful, please help us help others, and make a tax-deductible contribution to CET. For info, click the DONATE button to the left. All thanks, The CET Board.]

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What happens if you do light therapy too early? I have one day a week when I have to leave for work before my optimum light therapy time (as specified by the Auto MEQ on I am nervous about missing a day.

Do not be nervous: skip that day, rather than using the light too early. Almost surely, you’ll coast through OK.

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How do I know if I am suffering from depression or am only having a long mood swing?

From Mood Swings to Depression

The two are not mutually exclusive. If the mood swing is accompanied by certain other symptoms — which might include change in appetite and sleep, for example — and if it has lasted at least two weeks, clinical depression is a distinct possibility. For an initial self-assessment, use the Auto PIDS questionnaire at // Part 1 of the Auto PIDS is designed to determine whether any mood swings you have had in the past year, up to the present, might meet diagnostic criteria for a major depressive episode. (Parts 2-4 assess seasonality of mood swings, which may or may not be relevant in your case.)

If Depressed, Get Help

After you complete the Auto PIDS, you will receive immediate personalized feedback, interpreting your scores and itemizing your responses. The feedback advises whether it is important for you to see a psychiatrist, psychologist or psychiatric social worker for formal diagnosis and treatment. (Your GP also might be able to assist here, although, in general, GPs have less experience with this type of problem and less time to deal with it, so there is a possibility you will be quickly prescribed an antidepressant when it might not be indicated.) If you suspect you are currently experiencing a depressive episode, we suggest that you print out both the Auto PIDS feedback and itemization forms to show your doctor to get the discussion rolling.

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I am a flight attendant, so my sleep patterns are erratic. My work schedules are also varied — sometimes working early mornings and other times well into the night. I am a morning person, but obviously cannot confine my work schedule to just early hours. I tend to become depressed in winter — wanting to sleep from darkness on. I exercise regularly, but still feel tired and blue all winter long. Is there anything that will help?

Irregular Schedules: A Disadvantage

From the circadian rhythm vantage point, your irregular schedule presents a no-win situation (which, in the long run, could have deleterious effects on general health). Your winter depression probably should not be treated with light therapy, which could intensify the disruptive effect of repeated time-zone shifts.

Air Ionization May Be Better Than Antidepressant Meds

However, there are at least two treatment approaches that could relieve your depression. The conventional solution would be antidepressant medication (e.g., Prozac, Zoloft or Wellbutrin), for which clinical trials indicate at least partial benefit for SAD. On the other hand, we think you should also consider negative air ionization, a very promising non-pharmacological treatment for SAD (and possibly for depression in general) that has been tested successfully in three separate controlled trials at Columbia University Medical Center (info: Unlike for light therapy, we do not think the time of day of treatment is going to prove important. You could simply plug in the ionizer in your hotel room or bedroom whenever you go to sleep, and monitor whether your mood and energy improve.

Portable Ionization Units

While we are at it, let us mention another use for negative air ionization that has drawn interest from flight staff and frequent travelers. There is a battery-powered negative air ionizer, a bit smaller than a cigarette pack, that can be worn as a pendant or placed in a breast pocket (info: It directs the flow of ions upward around the head. Since such ionization is known to kill circulating pathogens in the air circulation, this method may reduce post-flight respiratory infections. (This method of ionization has not yet been tested for antidepressant action.) Several years ago, the flight attendants’ union expressed interest in having a formal trial conducted, but sponsorship was not forthcoming. Obviously, airlines might disallow staff from wearing ionizers, because it would draw attention to the ubiquitous problem of cabin air purity.

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I take Neurontin for chemical sensitivity. Do I need to adjust my light therapy use?

Neurontin (gabapentin) is an interesting drug. It was approved by the FDA for prevention of seizures. Although gabapentin is widely used to treat bipolar disorder (manic depression), the most carefully collected data fail to provide good evidence that it actually works as an anti-manic medication or mood stabilizer. Fortunately, in your example, there is no known reason that the use of light therapy and Neurontin would affect one another, so adjustment of your light dose is probably not needed unless you are experiencing light-related side effects.

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I am getting fairly good results with a light box, but because of complicating factors, not as good as I would like. I am considering going back on medication. Will I need to decrease my light dose as the medication becomes effective?

More likely, you will respond to a lower drug dose, because light has had a partial positive effect. It is always complicated adding one treatment on top of another — it can get almost impossible to know what is causing what. You need to convince your doctor that light therapy is an active, somatic treatment and should be conceived of as an adjunct “drug” when combined with pharmacological agents. In other words, both light and drug dose may have to be titrated in concert. Not to worry excessively about this, though, if you experience no side effects (including hypomania).

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Does SAD typically get more severe over the years? Is it common to have anxiety with it?

Many, but not all, SAD patients report worsening over the years, at least through middle age. SAD seems to be less of a problem during old age. We’re not sure why, but it could be that the depression becomes more chronic. Anxiety, tenseness and irritability are common in SAD, as they are in other types of depression. On the other hand, many SAD patients report being lethargic, apathetic and “vegged out,” rather than anxious. Although anxiety per se is not a defining characteristic of SAD, it improves as mood lifts with successful treatment.

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How does one choose whether to use light therapy, negative air ionization or dawn simulation for SAD? If one version of light therapy does not work well for you, does that mean the other also will not?

Up till now, post-awakening bright light therapy has been tested most extensively in clinical trials and received professional task force endorsement by the Society for Light Treatment and Biological Rhythms and the American Psychiatric Association, among others. It is quite possible that ionization and dawn simulation will be shown equally effective as bright light, but these are newer developments and the data base for them is smaller. Conservatively, we advise new patients to start with bright light therapy, and then move to (or add) the other methods as follow-up options. Yes, a given patient may respond to one, but not another, of these treatments. Presumably, bright light therapy and dawn simulation act by the same mechanism, and ultimately the choice between them may be based on convenience.

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Somehow, I feel like it is always winter. I have never been able to wake up early in the morning even with the sun out. (Making classes in college was a disaster). I drag around for half the day, although I seem to recover by evening. I cannot control my weight with any diet. I try to make friends, but cannot keep them. I feel so isolated.

Depression is a complex beast, and it can come with all kinds of patterns. Yours does look winter-like, and we know that for some people this symptom picture can last year round. There is a hint in what you say that light therapy could be effective for you regardless of the season. Your late waking indicates that your circadian rhythms are mal-synchronized with local clock time. This could be due to a genetic predisposition, but it also could be due to excessive light exposure in late evening – when you tend to feel better – because evening light can force the biological clock later, with resulting late awakening. For starters, make sure your indoor evening light is kept at a low comfort level that does not energize you. Whether the basic problem is genetic or environmental, morning light therapy could provide a solution by shifting your circadian rhythms earlier, just as it does for winter depression. You can expect to be able to wake up earlier, and there is good hope for an antidepressant effect. Indeed, a recent clinical trial at Columbia University Medical Center and Wesleyan University found that about half of patients with chronic, non-seasonal depression responded to light therapy just as well as SAD patients respond in winter. Definitely worth a try!

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I know I have depression, and I have been using Prozac for four years with some relief. Summers have been greatly improved, but especially in winter, I seem to fall apart. I do not think this is SAD, since I have also been depressed in summer. Can you tell me what is happening, and should I stay with the Prozac or do something else?

It is possible to have a “SAD overlay” on top of chronic depression that lasts all year. Winters are distinctly worse than summers, but summers remain symptomatic. Strictly speaking, you would not receive a diagnosis of SAD, because the diagnosis was designed for the simplest cases, where summers are problem-free. However, light therapy might still work for you in late fall and winter, and you could begin it as soon as you begin to slump, even while maintaining the medication. It is not impossible, however, that you could coast on medication alone, either at higher dose (which could be adjusted seasonally) or with an alternate drug.

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Do people who suffer from SAD usually have circadian rhythms that are somewhat “off”? I am just curious since you have said that the best antidepressant effect comes from resetting the internal clock earlier. Do people who have “normal” circadian rhythms tend to not get SAD?

On the one hand, we could say that the circadian rhythms are “off” during winter depression, in the sense that relief is obtained by shifting the rhythms earlier. Furthermore, come springtime, it appears that the internal clock spontaneously shifts earlier, at least for people who are “evening types” in winter. (To check your chronotype, take the Automated Morningness-Eveningness Questionnaire at On the other hand, SAD patients can be morning types, intermediate types or evening types — the same distribution that exists in the healthy, non-depressed population. What appears different about people with SAD is their mood lift when light therapy shifts the internal clock earlier, regardless of chronotype.

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If I buy a small light box with less lux output, is it simple math to adjust my sessions — for example, half the light output equates to twice as long in front of it — or is it not that simple?

Although there is a general trade-off between light intensity and exposure duration, no one knows the exact formula. (Manufacturers who provide a “linear solution,” like in your illustration, are just guessing, which is irresponsible.) All the relevant research has varied light intensity while the size of the box is kept constant. Box size introduces a major complication. With small boxes — which naturally tend to be less expensive — even slight head movements can remove you from the therapeutic range of light intensity. That is why we strongly recommend large-size screens. This is a case of “smaller is not better”!

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Does the effect of light therapy drop off after a while? I got great results (using all the wrong equipment and angles, not knowing any better) the first few days, and have had lesser results (with better equipment and correct angle) since.

In general, there is no build-up of tolerance with light therapy. Once you find your best dose, it should serve well in the long run. Many users do, however, titrate their light dose during the season — for example, more in January and February, less in March. An experienced user does this almost instinctively — you get a “feel” on a day-to-day basis for how much light you need. When you changed apparatus, you may have inadvertently dropped to a significantly lower lux level, in which case you may need to sit at the lights somewhat longer or use them earlier in the morning. In making such adjustments, it is smartest to stay with a particular combination of distance, duration and time of day for 3-4 days before switching, so you do not “miss” a positive result before it has time to develop.

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In the answer to question #1498 you wrote, “This is the time interval during which you can most easily reset your clock earlier, and such resetting is integral to the antidepressant effect.” If I am using light therapy to combat depression, and doing so resets my clock earlier — but for maximum effect I need to catch the end of my sleep cycle — does this mean I will gradually need to be doing my light earlier and earlier in the morning . . . sort of chasing the clock backwards, if you will?

Thankfully not! The recommended time is relative to your sleep interval before starting treatment. Once the initial adjustment is made, one can ordinarily keep the session time constant while maintaining the benefit. If you were to “chase the clock,” you would find yourself in the bizarre position of sleeping during the day and being awake at night — indeed, that is a strategy useful to night-shift workers in critical care occupations. But it is probably not for you!

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I am new (last 10 or so days) to light box use and am still learning the ropes of all the different variables. I also seem to be prone to the anxiety side effect when I get too much light. On any given day, is there any way to tell when I have gotten “enough” light? I have tried stopping “early” but have not gotten enough of the antidepressant effect. I would like to be able to stop just short of the anxiety starting.

First off, 10 days is too soon to know confidently how much light you will need to establish and maintain the antidepressant effect. Clearly, you should extinguish the lights at first inkling of an anxiety side effect, and set your session shorter on the following days. You may be able to sustain a longer session by sitting farther from the light box — try this in steps of 6 inches. If you can tolerate a short session (say, 10 minutes) in early morning, you can try adding a second short session at midday. If the anxiety persists after a few weeks of such testing, it is just possible that you will need to investigate an alternate treatment approach, such as negative air ionization (see or medication.

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When you say “optimal timing” of light therapy, what do you mean? What makes the timing “optimal”?

The timing of daily light exposure determines — along with light intensity and session duration — the strength of the antidepressant effect. We have learned that when light exposure causes the internal circadian clock to shift earlier, the antidepressant effect is enhanced. The sensitivity of the clock to light is a strict function of the time of day of exposure. The Morningness-Eveningness Questionnaire (AutoMEQ) at was designed to estimate optimal timing for each individual. Such timing can differ by several hours from one person to the next.

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Is there any correlation between core body temperature and SAD? I have noticed that my body temperature drops markedly when experiencing depression during the fall.

Body Temp in SAD and Depressed Patients the Same

A simple question with a complicated answer — sorry about that! Depressed patients often report feeling colder than when they are well. Investigators have measured core body temperature in SAD patients in both winter and summer. They have also compared patients with non-depressed control subjects in both seasons. Puzzlingly, they have found no differences, or even elevated temperatures in the patients.

Body Temp Variation

However, there is a possible explanation for your observation: come fall, the circadian rhythm of the body temperature may start to shift later. Normally, temperature is higher during the day than in the late evening and night. For someone who usually wakes up at 6:00 a.m., nighttime temperature gradually declines until about 3:30 a.m., at which point it starts rising toward daytime levels even before you wake up.

Variation Due to Time of Year

In SAD, the time of the temperature minimum may shift substantially later in the fall and winter, to about 5:30 a.m. Therefore, if you were to take your temperature at 6 a.m. during the dark months, it would probably be lower than when you take it at 6 a.m. in the summer. As sunrise moves earlier in the spring — this can be simulated by morning light therapy in the fall and winter — the internal circadian clock shifts the temperature cycle back to its summertime state.

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Is it OK to wear contact lenses while sitting in front of a light box?

It is OK, as long as the lenses are not colored or tinted (which would reduce the lux level). We advise not using contacts for the first few days of treatment (regular glasses would be fine), since some people initially experience eye irritation, which might be exacerbated with contacts. Either way, if eye irritation proves a problem, using artificial tears just before and after the treatment session sometimes helps.

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I used to be a night owl only — I could not fall asleep until 1-2 a.m. and then always had trouble getting up . . . until I had radiation treatment for cancer! After that, I became a complete morning person, waking at 5 a.m. every day and falling asleep by 9 p.m. every night. Now I have zero energy in the evenings after 7 p.m. Could the therapy have reset my clock? Could I use light therapy to readjust later?

Yes, and yes. Since the internal biological clock, which lies at the base of the brain, is a nucleus of oscillation neurons, it is possible that radiation altered its timing properties irreversibly. That does not mean your extreme morningness is irreversible, however. You could try light therapy — for starters, around 7 p.m., when the evening slump sets in. You may find that it gives a significant boost, which could allow you to resume a later, “normal” bedtime.

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I have been using a light box for the past three days, and have experienced a headache that lasts all day and into the evening. To reduce the lux level, I have sat farther back than required for 10,000 lux, and also reduced the exposure duration — procedures you have recommended for dose reduction and control of side effects. Still, the headache is bothersome enough to make me not want to use the box. Does this mean I cannot use a light box?

It is hard to know after only 3 days whether this will remain a problem. Often, but not always, headache that appears upon starting treatment spontaneously remits after several days. Also, it sounds as if you do not yet know whether you will obtain an antidepressant effect (with or without headache). You are smart in reducing the lux level and session duration. As a next step, skip the treatment for a few days to make sure the headache subsides. Then, beyond the measures you have taken, there are at least two more possibilities: (1) Try using the light at midday, and, if successful, edging gradually earlier over several days to find your comfort zone. (2) Order a set of short-wavelength-filtered wrap-around goggles, which reduce the aversive glare of blue illumination that might be triggering headache. These are inexpensive and available quickly over the web at We recommend the lightest filter, rated at 65%. Only rarely have patients had to quit light therapy because of intractable headache.

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In the question on “the mechanism of action of the agitation side effect,” one of your suggestions was to try light later in the morning. Could you explain more about this? It was the one suggestion that is not immediately obvious, if the point is to reduce exposure a bit.

To understand this suggestion, you need to learn a bit about the physiology of the internal circadian clock. The clock is maximally sensitive to light input — on average — during the last 90 minutes of habitual sleep (i.e., sleep without artificial early waking). This is the time interval during which you can most easily reset your clock earlier, and such resetting is integral to the antidepressant effect. After habitual waking, the clock gradually loses sensitivity over the next 3-4 hours. Thus, by using the light later in the morning, you can effectively reduce the treatment dose. (Alternatively, you can get a similar effect by using less light earlier in the morning.)

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How can I tell if the diffusion filter on a particular commercial apparatus is adequate?

There are two issues here. First, you want the screen to project fairly even light, so you cannot see the bare outline of the fluorescent tubes behind it. Second, the screen should not transmit significant ultraviolet (UV) radiation. Almost no manufacturer offers credible evidence of UV filtering; rather, they just make the claim and count on the consumer to believe it.

Technical Details of UV Exposure

One reason for this unhappy situation is that ascertainment of UV exposure is a technical matter — it is expensive to produce the data, and most consumers would not know how to interpret the data. If you are scientifically smart, you can challenge a manufacturer to show you a complete graphical spectral-output curve, starting in the low-UV range (around 200 nanometers) and extending throughout the visible range (up to about 750 nanometers). If there are any prominent bumps in the curve below 400 nanometers, you should reject the device. Two screen compounds, OP-3 and polycarbonate, have been shown to filter UV maximally, so you could look for devices with such screens.

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I have heard you can do light therapy through closed eyes, which would seem to be borne out, if dawn stimulators work. A friend says she turns on her box, rolls over to face it and goes back to sleep. It sounds heavenly compared to getting up at my unnatural hour. Can this really work?

It might work, indeed. There has been almost no research on such a treatment approach, however. The Columbia Clinical Chronobiology Group recently completed a large trial in which light was automatically switched on to full intensity, using a silent electronic appliance timer, for a short period before waking up. That is a much better idea than waking up to turn on the light manually, because sleep is not interrupted and the day-to-day timing of the treatment is held constant.

Use Dawn Simulator, but Flood Room with Light 

However, you need to use a light source that floods your whole sleeping area, so you catch the light regardless of your body position in bed. One such torchiere lamp is recommended on the CET Store page at It can be used with or without graded dawn simulation. Preliminary results of the Columbia trial were provocative: although the response to sudden switching on of the light toward the end of sleep was slightly less effective than treatment after waking, it worked very well for some patients.

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There is one brand of light box out there that combines light and ions. Would that be overkill? Could one somehow get “too much of a good thing” by combining the therapies?

We strongly advise against using that device. The combination has never been tested in clinical trials, and there could even be negative effects. Moreover, the design of that apparatus may be inherently faulty, since negative air ions flow to the best “earth ground,” which in this case is probably the light box itself. Not to mention that the lamps lack an adequate diffusing filter, and direct light upwards into the eyes (glaring “ski slope effect”). The supplier of this apparatus had acted irresponsibly in selling this device to depressed people.

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What is the correct way to measure the distance from the box, which determines lux level? If it is at eye level, then obviously it is just the horizontal distance in front of one. When it is above you, do you still just measure horizontal distance, or do you measure the diagonal from your eye up to the box?

The configuration we recommend — see the illustration under Bright Light Therapy at //— uses a tilted box, and we measure the distance horizontally on a plane between the eyes and the lower 1/3 of the screen, which is directly ahead. It sounds like you are raising an untilted box above your head, in which case the light would be projecting forward, not toward your eyes. That sounds non-optimal, and the distance rule would not apply. Rather, you would need to place a light meter that reads in lux at the position and orientation of your eyes as you take treatment.

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In the interest of saving money, what about making a light box with a conventional housing for fluorescent tubes and a standard plastic screen?

We strongly recommend against doing this unless you are a lighting engineer. The result would be uncalibrated light, very possibly with a significant ultraviolet radiation that could pose a hazard. Unfortunately, we have received horror stories from well-intentioned folks who built a box and suffered corneal and eyelid burns. It is not worth the risk. A good commercial light box, which can be had for less than $300, has been professionally calibrated and clinically tested. The cost is not that much greater than assembling components on the fly. Furthermore, with a doctor’s prescription for use in treating depression, there is now a fair chance that insurance will reimburse part or all of the expense.

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I am confused. A recent q&a item said that color temperature and spectral output matter. I understood your previous answers to suggest they did not — that any fluorescent bulb spectrum is fine as long as the UV is filtered out. Is this new info, or do I misunderstand? I am looking into buying a light box and am now unsure if one of my considerations should be the claims about spectral output?

As a general rule, any white or whitish fluorescent lamp will contain adequate spectral output for a positive treatment effect. It will project short, medium and long wavelengths. There is recent evidence that short wavelengths — in the blue or bluish range — mainly affect one (but not all) of the retinal receptors that input the circadian clock. That does not mean you should be seeking blue light, however. Seek a broad, balanced spectral output, which one obtains from tri-phosphor, multi-phosphor, daylight and softer fluorescent light. If a manufacturer is boasting about optimum spectral output of a particular apparatus, it is a sign of deceptive hyping. As for higher color temperatures (which project more blue), do not believe claims that they are better therapeutically than lower, color temperatures (which are more visually comfortable).

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In all of the books I have read regarding SAD, they show a dawn simulator that looks like a set of track lights. I have been looking for this type of dawn simulator for the last ten years and have never found one. Is this type actually available?

There are three separate functional components of a dawn simulation system: (1) the electronics that control the timing and intensity of the light; (2) the lighting fixture; and (3) the diffusing lens covering the bulbs. There is nothing special about a track-lighting design — it is an arbitrary selection of apparatus driven by the electronic controller unit. It is very possibly a bad choice, since the light aimed at the subject may not be diffused, and may also be highly directional (in which case even slight changes in sleeping posture might greatly reduce the light exposure). A configuration we have recently applied with success uses a commercially available standing lamp with an articulating arm for positioning a diffused light for optimum illumination of the pillow area. In addition, the unit provides upward illumination toward the ceiling, so the whole room brightens as the dawn progresses. For detailed info, see the store section at

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Most of the equipment referred to by your questioners, as well as that sold for depression treatment, uses fluorescent tubes. Have incandescent sources been used in trials? Would it be effective, since color temperature does not seem to be a factor?

There were a couple of very early clinical trials of bright light therapy for SAD, which used incandescent bulbs, but that avenue of R&D quickly died out. Fluorescent tubes are used in preference to incandescent bulbs for several reasons. Importantly, for the high therapeutic intensities involved, incandescent lamps would radiate too much heat to be practical. Secondly, most incandescent lamps provide imbalanced spectral output biased toward longer, reddish wavelengths of light, while most fluorescent sources provide peaks of energy throughout the wavelength spectrum.

Color Temp Matters 

In contrast to what you say, color temperature may indeed be a factor. For example, we are learning that the circadian rhythm system and the melatonin system are both impacted more strongly by shorter (bluish) than longer (reddish) wavelengths. We are not yet certain that the antidepressant system responds in a similar way, but a good guess is that it does. Our current recommendation is to use a “soft white” fluorescent lamp that contains both short and longer wavelengths. We warn against the use of intense blue light.

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The morningness-eveningness questionnaire (AutoMEQ) indicated my melatonin onset as 9:45 p.m. and my ideal light therapy session time as 6:30 a.m. I usually sleep until 8:00 to 9:30 a.m. (I usually go to bed around 11:00 to 11:45 p.m.) Can I do light therapy in the late morning, like around 10:00 a.m.? Or will I need to change my whole morning routine in order to do light therapy?

Sleep Long, Wake Early

Everyone who is a “long sleeper” — in your case, around 10 hours — will have the same reaction to the MEQ’s recommendation that you wake up earlier for the most successful treatment. (This is not a problem for shorter sleepers — say, 7 hours.) There are two considerations here. First, do you sleep that long in the summer, when you are not fighting depression? If your long sleep is restricted to the fall and winter, you should associate shorter sleep with higher mood and energy. Second, we have learned that the response to light therapy is strongest when the treatment resets the internal biological clock to a significantly earlier hour.

Experiment with Times/Duration of Sleep

In general, such shifts occur around 9 hours after melatonin onset — which, in your case, lies in the range of 6-7 a.m. You can try using the lights at 10 a.m., but you may not achieve an optimum response. However, you could start a bit later than 6:30 a.m. — say, 7 a.m. — and still get full benefit. After trying this for a few days, you may find that you are quite comfortable with the reduced sleep duration. On the other hand, you may find that you want to adjust your bedtime somewhat earlier — say, 10:30 p.m. — to partially compensate for the morning sleep loss. Play around with it, to find out what works best for you, but maintain each test schedule for at least 3-4 days before switching.

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Can you tell me if sunbeds help in treatment of seasonal affective disorder?

The provisional, but strong answer is No! The essence of light therapy is enhanced illumination of the eyes at appropriate intensity, duration and time of day. The essence of sunbed use is ultraviolet radiation of the skin, with the eyes covered. Apart from no demonstration of efficacy as an antidepressant, the consensus of dermatologists is that use of sunbeds should be avoided altogether to avoid risk of skin cancer. Don’t let suntan parlors tell you otherwise.

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What is delayed sleep phase disorder (DSPD)?

DSPD is a circadian rhythm disorder in which the internal body clock is synchronized abnormally late with respect to local clock time, making it virtually impossible to fall asleep at a conventional hour (say, between 10 p.m. and 12 midnight vs. 3-5 a.m.). In some cases, this is a lifetime disorder, caused by a genetic predisposition, and it can run in families. In other cases, a person slips into delayed phase by purposely staying up unusually late and sleeping in a darkened bedroom without early morning bright light exposure. Sleeping pills do not solve the problem. Careful use of bright light therapy can be effective.

Delays, but not Extreme

For those without extreme delayed phase (say, with sleep onset between 1-2 a.m.), a good strategy is to estimate current circadian rhythm phase using the Automated Morningness-Eveningness Questionnaire at The results will show a time in late morning when light exposure should be used to begin resetting the internal clock. Every few days, the treatment can be moved earlier (say, in 30 minute steps) until sleep onset normalizes.

Extreme Delays

The Questionnaire is not designed for those with extreme delayed phase, however. In such cases, light therapy should start around the time of spontaneous waking (say, 1 p.m.), and stepped earlier as described above. Successful application of these methods, taking into account individual differences, may require supervision by a specialist. In some cases, it is appropriate to take a low dose of melatonin 12 hours before the scheduled light therapy, for a synergistic effect.

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I take a low dose birth control pill and have been advised to stay out of the sun to avoid brown marks (“mask of pregnancy”) on my face. Will a light box cause the same marks?

The vast majority of drug-light interactions in the skin are triggered by ultraviolet (UV) radiation. An acceptable light box assiduously filters out such energy, thereby eliminating or greatly reducing the risk of photosensitization. Any plastic screen on a light box will filter out some UV, but how much is a question that requires spectroradiometry. Spectroradiometry is a specialized laboratory technique that measures energy transmission throughout the UV and visible range of light wavelengths.

Beware UV-free Claims

Unfortunately, many manufacturers claim their systems are “UV-free” without providing supporting data. We know of only two light box filters that have been demonstrated to do the job adequately (OP-3 and polycarbonate based). The cautious consumer will look for those specifications or demand to see a printout of a spectrogram that shows near-zero transmission of wavelengths below 400 nanometers. All that said, there are some medications that photosensitize in the short-wavelength “far blue” visible range between 400-450 nanometers, so it is important for your doctor to ascertain whether a UV-filtered light box may still pose a risk.

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Exactly how far from a 10,000 lux light box should I sit, and where should I place it? It is 2-feet wide and 1-foot high. Do I place it above eye level? Stare directly at it?

Light Boxes in General

The lux level at your eyes depends on your distance from the light box screen. There is no such thing as a “10,000 lux light box;” rather, a light box may be capable of providing 10,000 lux if it has appropriate dimensions, number of lamps, lamp power, filtering, etc. Some manufacturers give deceptively high lux measurements, made with an instrument that focuses narrowly into the lamps, whereas the eyes take in the whole illuminated environment. That problem is especially true for recent, relatively tiny lighting devices, which we do not expect are therapeutically active.

Your Light Box

A light box of 2 x 1 ft may be adequate; it depends on the bulbs inside, the screen filter and the distance. You have to trust the manufacturer for specifying the required distance and unfortunately the information given is not always accurate. We always recommend that the box be placed at or above the line of sight in order to project light downward toward the eyes. Boxes that rest on a tilting stand are best. Such an arrangement greatly reduces aversive glare of the high intensity light. One should never stare directly into a light box, but instead orient forward and concentrate on reading, writing, breakfast, etc., in the illuminated field. For more info, see the “Suppliers” page at

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I am ready to purchase a 10,000 lux light box, but am still confused about wavelength vs. degrees Kelvin (K) and full- vs. broad-spectrum light. If around 2800 degrees K is yellow-red and 11,000K is very blue, what is ideal? One unit I am considering specifies 3000K — would that be too yellow? Are the terms broad- and full-spectrum equivalent? Is it not true that both include all the colors — or, if colors are determined by wavelength, which ones are harmful? I know these details seem academic, but my eyes and skin are extremely sensitive and burn very easily. I would not be able to use a light box that failed to filter out all the harmful “rays.”

Color Temp

It would take a long essay to answer your important questions in detail. So let us try to give the bottom line. The higher the color temperature, the greater the representation of short wavelengths of light in the violet-to-blue range. Think of the “daylight” standard as about 6500K. Perceptually, that is a crisp, cool white. 3000K is a softer white with a slight pinkish tinge. Depending on the particular fluorescent bulb, the coloration is determined by a set of phosphors that fluoresce in relatively narrow wavelength bands. One needs to examine a graph of the wavelength pattern to determine how a given bulb mixes particular phosphors to create the overall coloration. While a 3000K bulb appears soft and easy on the eyes, it still contains a phosphor that emits photons in the short-wavelength blue range. So, do not listen to manufacturers who claim that higher color temperatures are “better” because they contain more blue. There is no clinical evidence for such claims. Light of lower color temperature has been thoroughly tested for clinical response, comfort and safety.

Full vs. Broad Spectrum

“Full spectrum” is a hyped term used in misleading advertising. It has a relatively high color temperature — white with a bluish tinge — and was originally developed actually to boost UV output, which can cause skin puffiness (erythema) and even burning under 10,000 lux conditions. There is absolutely no evidence that full spectrum bulbs have a therapeutic advantage. “Broad spectrum” merely means that a wide range of phosphors are activated to create a white, or whitish, light. Any light box, regardless of color temperature, should include a smooth diffusing screen that filters out 99% or more of ultraviolet (UV) radiation, the source of tanning. Long-term exposure even to low levels of UV constitutes a potential hazard to both eyes and skin, and must be avoided. We say: if you are choosing a light box, challenge the manufacturer to show you a graph of spectral output including the UV range between 200-400 nm, and make sure there is negligible UV transmission. So, we did write you an essay! . . .

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I work in our local cancer research center. A lovely man comes in who may be suffering with SAD syndrome. 1. Should he first be diagnosed by his GP? 2. Could he obtain the light box at our local pharmacy?

Your client should first complete the PIDS and MEQ online questionnaires at //, hosted by the nonprofit professional agency, the Center for Environmental Therapeutics. The questionnaire feedback will tell him whether his seasonal slumps have clinical severity, and — if so — how to treat them with light therapy. (His cancer status is irrelevant.) He can print out the results to discuss with his doctor and make decisions toward next steps. Appropriate lighting apparatuses are available at some pharmacies, but not most. Some, indeed, are selling “hyped” devices that have never seen clinical testing and are likely to be ineffective. See the same website for guidelines on choosing a light box — their “Suppliers” page — and their clinically tested recommendation on the “CET Store” page.

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I experience advanced sleep phase syndrome (ASPS) in addition to SAD. My understanding of SAD is to treat it with morning light. My understanding of ASPS is to treat it with evening light. Which time of the day should I schedule my 30-minute light box treatment?

This is a terrific question. For our readers, ASPS is a circadian rhythm sleep phase disorder in which one falls asleep unusually early (say, 8 p.m.) and wakes up unusually early (say, 3 a.m.). To set the circadian clock to a later hour, light therapy has to be taken around the start of the “subjective night” (say, 8 p.m.), because morning light could shift the sleep cycle even earlier. On the other hand, light therapy for SAD is most effective at the end of the subjective night (say, 6:30 a.m. for a normal sleeper), and even those with a strong morning chronotype benefit most from morning light. (For a determination of your chronotype, complete the Morningness-Eveningness Questionnaire at

The chronotype of people with ASPS falls outside the range of normal chronotypes, and their antidepressant response to morning vs. evening light has not been adequately investigated. This may be a case where treatment should be scheduled in both morning AND evening, as was the original formula for SAD treatment. The specific timing of the two treatment sessions would need to be determined by a specialist, with the goal of delaying the sleep episode while maintaining morning exposure (in the case above, at, say, 6:30 a.m.). One technological means to implement such a schedule is with a dusk-to-dawn simulator used to straddle the sleep interval in the bedroom. A high-intensity dusk signal could be followed by a lower intensity dawn signal, to achieve an optimum balance. We definitely need more research on such applications.

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What is the relationship, if any, between negative air ions and ozone?

There is always some ozonization when negative ions are produced. Depending on the design of an ionizer, the level may be appreciable or negligible. The ionizers that have undergone controlled clinical trials for seasonal and non-seasonal depression produce negligible ozone levels (well below safety cutoffs) that dissipate in the immediate area of the ionizer electrodes. All that said, however, one sometimes reads claims for a specific therapeutic-psychoactive benefit of high levels of ozone. Such claims are unsubstantiated in the scientific literature, and such treatment should be avoided.

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If a SAD person sleeps with the bedroom window covered to block night street lights, will their ability to wake in the morning be affected?

Yes, indeed. The brain needs to receive an early-morning light signal to keep sleep behavior synchronized with the external day-night cycle. That is at the heart of the light therapy effect. People with street light invading their bedrooms therefore are faced with a Catch 22. You are smart to keep your bedroom dark during the night, but you are doing this at the expense of missing the natural dawn signal. The best technological work-around is artificial dawn simulation, as described at // An additional benefit of dawn simulation is that you can “force the sun to rise in a springtime pattern” while it is still dark outside in winter, which is a proven therapeutic maneuver.

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Has the amount and timing of melatonin supplements been established for treating SAD?

Despite many press accounts to the contrary, clinical trials thus far have not demonstrated efficacy of melatonin for treating SAD — and we do not advise that you take that course.

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Fall has arrived. I still feel OK, but I am trying to decide when to start light therapy. Should I start with the time change?

There’s no magic about the date of time change. Some people with SAD, or those with the less severe winter doldrums, begin to feel down well before the time change, while others feel well till much later in the season.

There are two strategies to consider: (1) On the basis of your personal seasonal history, start the treatment shortly before you usually begin to feel fall/winter symptoms — say, one week beforehand. This is a “prophylactic” strategy aimed at preventing the onset of the winter episode altogether. The drawback is that you cannot predict exactly when the episode would begin, so you might be engaging in unneeded treatment.

(2) Wait till mild symptoms begin to set in, and then immediately start the treatment. Most often, people begin to feel sluggishness, increased sleep pressure and heightened appetite for carbs weeks or even months before depressed mood appears. If you use this strategy, you can be more confident that you are treating actual symptoms of the fall/winter episode and you can verify subjective improvement once the treatment starts. Usually, we recommend the latter strategy.

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There’s no magic about the date of time change. Some people with SAD, or those with the less severe winter doldrums, begin to feel down well before the time change, while others feel well till much later in the season.

Color Temp

The term “full spectrum” is not precisely descriptive of the light quality of a unit. More specific is the color temperature (e.g., 3700K, 5000K or 6500K). All these color temperatures can be effective in light therapy or for task lighting. The higher color temperatures contain more short wavelengths, i.e., the blue component of white light. The photons emitted by fluorescent bulbs, whether the tubular or screw-in type, are no different from one another at a given color temperature.

Proper Light Level

What is most important in selecting a light box is to ensure adequate light level, smooth diffusion of the light through a filtering screen, and positioning of the light at and above (NOT below) the line of sight. A given unit might be used effectively for task lighting or light therapy. For task lighting, it is important to ensure that the light level can be switched up or down, since one would not want to maintain maximum light therapy intensities for long durations during the work day.

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Where in my area can I find help planning the schedule I need to treat delayed sleep phase syndrome once I get the lamps? What kind of doctor should I seek?

First things first. First, the doctor and the diagnosis. Then, determination of the most appropriate treatment strategy. Third, selection and purchase of the most appropriate lighting apparatus — if light therapy is indicated. The lighting regimen for treatment of delayed sleep phase syndrome must be individualized for each case. For the doctor, contact the Sleep Disorders Center or Sleep Clinic at your local university teaching hospital. Such clinics exist at most major medical centers in the U.S. If your doctor is inexperienced with light therapy for circadian rhythm sleep disorders, you might suggest that he or she consult the chapter on Light Therapy in the book, Principles and Practice of Sleep Medicine.

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I have suffered from delayed sleep phase syndrome since I was a little girl. I am now 46 and suddenly too old to live with 4 hours of sleep every weeknight. I am so exhausted that all I want to do during the weekend is sleep my natural hours, 6 a.m. to 2 p.m. Unfortunately, during the week I have to get up before 6 a.m., but even as sleep-deprived as I feel all day, by midnight I get a second wind. I rarely ever fall asleep before 2 a.m., and then I keep waking up because I am usually hungry at that time of the night. I have tried pills, melatonin, etc. I want to try light therapy. Any advice as to what kind of lamp, how long to use it for, at what time?

Word To The Wise: your present weekday schedule reinforces your “circadian sleep phase disorder,” because you are now receiving light exposure at a time of day (approximately 6 a.m. to noon) that forces the internal biological clock later, when you need it to be forced earlier. Light therapy may indeed be right for you to try at this point. It has helped many patients with this problem, by re-synchronizing the internal clock with external solar time. Whether you could do this successfully on your own is a big question, since the lighting schedule has to be continually adjusted until you meet your goal (for example, easy sleep onset at 11 p.m.).

Intensive Therapy Needed 

In our experience, progress and schedule need to be monitored by a clinician who can advise “next steps” every few days for the first few weeks. Furthermore, at the start, you would need to devote some continuous vacation time to the treatment, because the lighting schedule would begin toward the end of your “subjective night,” around 1 p.m., with 30- to 60 minute exposures, and move successively earlier every few days, possibly in 30-minute steps. (Sometimes faster progress is feasible). Additionally, you would have to carefully minimize room light exposure after 11 p.m., allowing yourself only enough light to comfortably read, watch TV, and sleep in darkness.

Proper Use of Melatonin 

You say that melatonin did not work for you, but that could easily be due to inappropriate scheduling. A dose of slow-release melatonin (no more than 3 mg), taken 12 hours before the scheduled light therapy, might greatly expedite the re-synchronization process.

Try Dawn Simulation

As for recommended lighting apparatus, see Once you re-synchronize, you may benefit from maintenance treatment with dawn simulation (also described on that website) scheduled for about 4:30 to 6:00 a.m. None of these procedures constitute a “cure,” in the usual sense of the word; rather they are correctives that you would always need to maintain.

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I live near Syracuse. Needless to say, cloud cover is intense. I have been suffering depression more acutely since moving here, especially since my second pregnancy. Although I am receiving good treatment with a psychiatrist and work hard to do everything I can to moderate my depression, it is hard. Would moving to a sunnier climate help me? This is something my husband and I are considering.

Winter depression is statistically less prevalent in the southern U.S. than in the middle and northern states. However, it is not completely absent there. If your depression were to respond to light supplementation — indeed, regardless of the season — you might be better off down south. However, some patients have tried this without success (and decided to move back north and use artificial light therapy instead). Trying out light therapy is the first sensible step, since it would quickly tell you whether moving your family might be worth the effort and expense. If the treatment worked, the next step should be an extended vacation in the sunnier climate, to determine whether the change in location is helpful. Only as a third step, then, would we recommend making the move!

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Why is it that drug therapy for SAD should not continue year-round, as you say in question #1337? I have heard from a depression expert that one should not go on and off antidepressants, since you risk less efficacy each time you do.

If you are currently treating a depressive episode, or are vulnerable for experiencing one even after you have responded to an antidepressant, it is a big mistake to go on and off meds. That does not apply for SAD patients in late spring and summer, and we believe it is wasteful — and bad medical practice — to continue using antidepressants at those times of year. If you have responded to Brand X one winter, it remains likely that you will respond to it again the following winter.


Some doctors prescribe antidepressants year round just in order to maintain compliance — that is, to get the patient into a daily, automatic habit of taking the pills. We give SAD patients more credit than that, to know which half of the year the meds are needed. Some doctors want to avoid any chance of seasonal relapse, which might occur if patients are off meds in the fall. To address this problem, there are studies underway that begin medication in the early fall, while patients are still feeling well, with the aim of preventing onset of the late fall/winter depressive episode. Even then, the medication is discontinued in spring, once the vulnerable period has passed.

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What is the difference between color temperature and the color rendering index (CRI)? Which is more important for light therapy?

Color temperature reflects the distribution of wavelengths of light produced by a bulb. The white or whitish light used therapeutically is created by a particular set of phosphors that fluoresce in the tube, and these vary widely. Successful treatment has been obtained across a wide range of color temperature, from about 3000 degrees Kelvin to 6500 degrees. (Important note: higher does not mean “better”!) Outside that range, we see distinctly colored light, red or blue, which we do not recommended for light therapy at high intensity. The CRI measures how accurately you will perceive colored objects — say, clothing fabric or skin tone — in comparison with how you would see them in outdoor light. This, in itself, is not important for light therapy — unless, of course, you are working on an oil painting while taking the treatment!

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What is the likelihood that individuals with light sensitivity (photophobia) can also have SAD? The fall/winter months have been consistently difficult for me, and I am under treatment for depression. I find that I have to wear a hat and sunglasses whenever outside (even on overcast days), otherwise I get headaches. My ophthalmologist assures me that photophobia is common to those with blue eyes (like me). Are SAD and photophobia mutually exclusive? If not, how does one treat SAD without exacerbating this disturbing side effect?

The lightly-pigmented irises of blue eyes, in comparison to brown or black eyes, admit far more photons into the eyes. Many SAD sufferers are blue-eyed. (Think Scandinavia!) Because of this sensitivity, you may find that a light therapy dose less than 10,000 lux is fully effective. That simply requires sitting at further distance from a light box rated at 10,000 lux. Photophobia may result primarily from the short-wavelength component of white light, whether outdoors or from fluorescent sources.

Apparatuses Which  May Help

It is worth trying inexpensive wrap-around filters to see if they alleviate the problem. For example, NoIR sells an ultraviolet- and blue-blocking filter ( which, at the 65% rating, maximizes light transmission above the short wavelengths. Another therapeutic alternative is dawn simulation (see //, which is based on low-intensity incrementing light delivered toward the end of sleep. Even then, however, blue-eyed people often need to adjust the light level below that used by their dark-eyed counterparts.

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I started using a 10,000 lux light box last fall with dramatically positive results. Because I felt better during the winter with the light box than I usually do during May, June and July, I concluded that I would benefit from year-round use. Given the longer hours of daylight now (May) can I be getting too much light?

You will know if you are getting too much light if you become speedy, hyper, or high to the point that you’re slightly out of control (“hypomanic”) . . . or if you start having insomnia with unreasonably early waking. In most cases of SAD, patients sense correctly that they no longer need supplementary light exposure by early May. That said, however, new investigations are pointing to year-round use of light therapy by patients with chronic (non-seasonal) depression. In certain circumstances, then, this strategy can be useful.

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Can too much neon light be bad for you? I live under a huge neon sign that shines through my windows all night.

Your own sleep quality, daytime energy and mood state comprise the acid test of whether such nocturnal illumination is bad for you. In general, we would predict it would indeed be bad. We call this “nocturnal light pollution.” We believe it is important for bedrooms to be dark during the beginning and middle of the sleep period. Toward the end of the sleep period, however, exposure to gradually increasing dawn light — whether through the window or from an artificial dawn simulator (see // — can help stabilize sleep, make waking up easier, and enhance daytime mood and energy. Your neon sign will not do this job.

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I suffer from a VERY serious condition of summer depression. Each year around this time (April) I start to become very worried about the bad weather that is due. What can I do, and how can it be cured?

Our New York area survey suggested that summer depression occurs only at about 10% the rate of winter depression. Our best understanding is that (1) it is not responsive to light therapy, (2) standard antidepressant medication is probably indicated. Some patients have reported temporary — but major — relief by staying in cold, air conditioned environments as much as possible. However, their mood is likely to plummet when they go outdoors. Sad to say, there has been very little research on this “minority” seasonal pattern.

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I am so grateful for the study that came out in 1998 showing that light therapy works on the backs of the knees as well as through the eyes because I can use a regular low-cost fluorescent light instead of the expensive ones. I use my light between 3-5 PM for controlling evening food cravings. So far I have lost 15 pounds just by not eating junk food at night. Why is this effect not more well-known? People can have food cravings even though they do not have depression, right?

We’ll answer your question in two parts (and hope we do not quell your enthusiasm too much!) (1) Sad to say, the “light behind the knees method” has not been replicated, despite many attempts since the original, highly publicized publication appeared. The main effect reported was for circadian rhythm phase shifts, i.e., moving the internal clock earlier or later with timed lighting. That has not been replicated. Second, investigators thought that if the phase-shifting effect were real, light behind the knees should also suppress the production of melatonin by the pineal gland, just as retinal light does. However, despite several attempts, no one has been able to suppress melatonin with light behind the knees. Finally — and most importantly for this discussion — despite several attempts, no one has been able to demonstrate a specific antidepressant effect of light behind the knees. Even with these clinical failures, however, light behind the knees could exert a strong placebo effect, which is probably why some people who have tried it believe it “works.”

Stick with Light Therapy for Eyes

Our strong advice is to stick with bright light therapy to the eyes, using a carefully designed light box. (Important design factors are outlined at Yes, this may cost more than placebo light to the knees, but we know it works better than placebo! (2) You are correct, indeed, that food craving (and eating, even bingeing) can occur without depressed mood. Furthermore, these problems can occur seasonally, peaking in winter, even in patients who do not have SAD. There is every indication that light therapy helps to reduce such winter cravings, even with dramatic reductions in binge eating. In your case, however, it sounds like self-control of your nighttime food intake has been the major factor helping you to reduce weight. Great!

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What is known about the effect of electromagnetic radiation (EMR) from sitting so close to a light box? I have noticed some products mention being grounded in such a way or having some kind of filter to reduce the radiation.

Our lighting engineers say not to worry about EMR from standard fluorescent light boxes; that no special filtration or grounding is needed. The light boxes used in our studies (see, e.g., were evaluated for EMR by the responsible New York State agency, and found to show minimal emissions, well below established hazard levels. We believe that commercial advertising of such a need is alarmist and unwarranted, intended to boost sales of a specific expensive product.

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From what I gather, UV light is not a necessary component to help combat the symptoms of SAD or clinical depression. Is this correct? My eye doctor proposes that patients who are prone to depression should avoid using contact lenses with UV light protection. His claim is that UV light, although damaging on many levels, helps to combat SAD. Is this in fact true? My favorite contact lenses have UV protection, and he is proposing that they may not be the best bet for me.

Your eye doctor is simply wrong. There is no known antidepressant benefit of UV radiation in combatting SAD. The antidepressant effect occurs fully in the visible range of light wavelengths. A popular impression — thanks to unscrupulous vendors — is that “full-spectrum” fluorescent bulbs, which are designed to emit UV and a high balance of far-blue wavelengths, are somehow especially effective for treating SAD. Wrong, and we advise against using them. These bulbs are inefficient, very expensive, and produce less lux per kilowatt hour than fully effective bulbs (see Don’t worry about your contact lenses, and please correct your doctor.

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My husband has been diagnosed with SAD. His doctor told us it is okay to purchase a light box for therapy. He has some retinal problems. Any suggestions as to what we should look for or avoid?

It depends on the particular retinal pathology. You should not proceed without consultation with (and concurrence of) your ophthalmologist, and you should engage him/her for periodic monitoring. It would be a good idea to make sure there is a fundus photograph in the chart before beginning treatment. All that said, however, there are no specific retinal counter-indications for light therapy.

Lighting System Options

Some retinal problems make the eyes particularly sensitive to visual glare, so it is especially important to select a lighting system with a smooth diffusion filter. Light bulbs should be of relatively low color temperature (in the range of 3300 to 4500 degrees K) in order to de-emphasize high-energy blue irradiation, which can exacerbate glare. Maximum ultraviolet filtration is also very important. A system we have evaluated successfully in clinical trials, and which meets these standards, is described in detail at That site also discusses criteria for comparison shopping for light therapy apparatuses, and includes an on-line questionnaire to help you make an initial determination of optimum timing for treatment.

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I am looking into light therapy, not so much because the days are short, but because I work in a place with no windows. It is light out (and usually sunny) when I get up in the morning, so I am considering simply going outside in the mornings. How does 10,000 lux for 30 minutes compare to exposure to outdoor light? In other words, how much time in sunlight would be equivalent? What about a cloudy day?

Your suggested strategy — an outdoor walk before work — makes a lot of sense, but there is no simple way to know how much is equivalent to light therapy. There are some relevant observations, however. 10,000 lux is measured on a horizontal surface of the earth — from global clear skylight illumination (i.e., not directional from the sun) — about 40 minutes after sunrise. In one case study, where a volunteer attached a light meter/data logger to a sweatband over his forehead, he received far more light from 30 minutes of light therapy than he ever received outdoors. Almost surely, that is because people don’t look up at the sky consistently. It may be possible to relieve the daylight deprivation of windowless indoor environments using a light box designed for work stations, with a variable intensity control. An example is the DayLight XL (see the CET Store page).

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How long should you be treated with an artificial sunlight bulb?

We do not recommend treatment with “bulbs” per se, but rather with light therapy systems that include a wide spread of diffuse illumination of appropriate intensity directed at an angle from above the line of sight. Furthermore, we do not recommend use of bulbs designed to mimic sunlight, because they can emit ultraviolet radiation with an intense blue component in the white, neither of which is necessary or conducive to the treatment. For an example of the type of system that is optimum for light therapy, check out // As for the timing of treatment, this is a highly individual matter. The same website also offers general guidance using the Automated Morningness-Eveningness Questionnaire, but adjustments under clinical supervision may be necessary.

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Is it safe to use a light box if I am on intravenous antibiotic therapy with doxycycline for Lyme Disease? I have been instructed to avoid sunlight.

You can use light therapy, but you must use a system that completely shields ultraviolet (UV) light exposure. There is only one such 10,000 lux fluorescent system that clearly meets these standards (for info, see // In the future, other possibilities may include head-mounted units with light-emitting diodes (LEDs) to generate the signal without UV, however such units have not yet been demonstrated effective relative to placebo controls for antidepressant treatment. One final clinical note: some patients who have responded well to bright light therapy report that their mood worsens and the light becomes aversive while they are taking antibiotics for acute infections. Whether this might also apply to Lyme disease, which is more chronic, we simply do not know.

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Why do I always wake up at 4 a.m. no matter when I have gone to sleep?

You have a strong internal circadian rhythm signal for sleep offset! Two major independent factors influence the time we feel ready for sleep and when we awaken spontaneously (without alarm clock): the amount of accumulated sleep debt — which often increases during the work week — and an alerting signal from our biological clock. Although both factors are always at work, someone with a relatively strong internal clock signal will wake up at the same time whether sleep debt is high or low. The timing of the internal wake-up signal can be adjusted by light. Assuming that premature awakening at 4 a.m. is not due to depression or anxiety, bright light therapy in the evening shortly before habitual sleep time can set the clock to wake you up at a later hour.

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Even after a good night’s sleep, I have trouble waking and getting out of bed in the dark, yet, regardless of the hour I retire, I can arise when it begins to get light out. My day demands that I get up before dawn and I am deeply disturbed over this long-term issue. I long to simulate the dawn; can your lights do that for me?

Naturalistic dawn simulation is indeed designed for the purpose you describe, above and beyond its use as an antidepressant. A dawn simulation system comes in two parts: microprocessor controller and light fixture. The system used in our clinical trials is pictured on // That site lists a commercial supplier. The lighting fixture used in our clinical trials is not currently commercially available. Instead, we recommend a lamp described at


For this specialized application, do NOT use the separate dimmer cable that comes with the lamp. Instead, plug the lamp directly into the control box output receptacle. Position the downward-facing diffuser lens in the direction of your pillow from a distance of about 40 inches. Intensity of the dawn signal can be adjusted either by moving the lamp farther away or resetting the “percent output” level on the control box

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Are light visors effective in treating SAD? I have found one that emits 2500 lux. Is this light output strong enough to counteract SAD?

In principle, 2500 lux from a visor should be effective, although it would require far longer daily exposure duration (around 2 hours) than using a 10,000 lux light box (around 30 minutes). Such lower light levels were typical of first-generation light boxes that gained wide use about 15 years ago. However, attempts to demonstrate visor efficacy for treating winter depression have been hampered by the failure of controlled studies to show any benefit from low-level “placebo” light. The problem may lie in the narrow area of illumination projected by the visor, which could result in non-optimal illumination of the retina of the eye. Future design enhancements of visors may yet solve this problem.

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I suffer from SAD and was wondering if UV light (from a sunbed) has any benefits?

As best we know, the mechanism of action of light therapy for SAD is through visible (not UV) light to the retina of the eye (not the skin). Addition or subtraction of UV light using standard light boxes makes no difference in the antidepressant effect. Beyond this, cumulative UV exposure to the eyes or the skin presents well-known health hazards, and thus it should be avoided when seeking relief from SAD. Indeed, it is important to ascertain that any light box used for SAD treatment maximally filters out UV (and there are several on the market that fail to do so).

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I’ve noticed that light therapy boxes (LTB’s) have uses for SAD, but I have heard that they can be effective with insomnia. How do you use LTB’s on someone with early, middle or late insomnia — especially late insomnia to stop my brother from waking at 4 a.m. every morning. He doesn’t want to use medications.

You are correct that light therapy can alleviate certain forms of insomnia, when the root cause is misalignment of internal circadian rhythms with the day-night cycle. Waking up at 4 a.m. could be due to several other factors, however, in which case light therapy would be ineffective. Diagnosis and treatment supervision by a sleep specialist is advised. A recent medical handbook chapter on the topic, which you might recommend to your doctor, is: Terman M, Terman JS. (2000) “Light therapy,” in Principles and Practice of Sleep Medicine, third edition by Kryger M., Roth T., Dement W., Editors, Philadelphia, W.B. Saunders, pp. 1258-1274.

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Does seasonal affective disorder subside in more temperate climates?

Although exceptions to the rule have been reported in some surveys, in general, SAD hits more people the further north they live (in the northern hemisphere). For example, one major study projected 5 times as much SAD in New England than in Florida. An implication is that a SAD sufferer might do well to move south. Problem is, that doesn’t guarantee problem-free winters, since a fraction of the population still develops symptoms down south. Before you move, you should test your selected destination with an extended winter stay — not just a one-week get-away!

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What is the cost of this light apparatus to the patient?

Research volunteers in all our clinical trials are loaned the treatment apparatus (light box or negative air ionizer), for use at home, without cost. The apparatus must be returned for use by other participants when the trial ends, but if one wants to continue treatment, there is a discount arrangement for purchase of a similar apparatus, offered to our research volunteers by distributors.

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What exactly is “chronobiology”?

The Science

Chronobiology is a science that studies how the clock inside the brain interacts with time cues in the environment. The daily alternation of light and darkness is the main cue that keeps our inner clock in synch with the outside world. When such cues are absent or weak, our circadian rhythms of body temperature, hormones, sleep and alertness — and yes, even mood — get out of adjustment with earth’s rotation about the sun.

The Technologies

Methods used in clinical chronobiology include timed exposure to bright artificial light to reduce insomnia or sleep-wake disturbances due to shift work, and the use of a spring-like lighting environment to fight winter depression. New applications include light therapy for chronic depression and depression during pregnancy. The underlying idea is that even when there is plenty of light outdoors, our urban lifestyle tends to keep us in the dark, relatively speaking, making us vulnerable to mood slumps.

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I was just wondering what your studies have shown on the application and effectiveness of broad vs. full- spectrum light box sources for bright light therapy solutions. From what I have read, it looks like full-spectrum might be the way to go as long as the light source is radiation- shielded and grounded. What do you think?

We moved away from use of full-spectrum light more than 10 years ago, and we recommend against it! Full-spectrum lamps do not produce antidepressant effects greater than broad spectrum lamps. At the high intensities used therapeutically, full-spectrum lamps boost unwanted short-wavelength radiation including unhealthful UV, which can cause immediate skin damage (redness, puffiness) in sensitive individuals and which pose a long-term cumulative hazard both to the skin and eyes. Furthermore, such lamps produce less total light per watt (that is, they are electrically inefficient) and are far more expensive than broad-spectrum alternatives. The light sources used in our clinical trials screen out UV radiation and are far more comfortable for treatment at high intensity (10,000 lux).

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How do the lights work?

Scientists are still investigating the precise mechanism that makes light therapy effective. Thus far, we believe that bright light works to reset the body’s internal clock, the “circadian rhythms” that control body temperature, hormone secretion and sleep patterns. Melatonin is a nighttime hormone that plays an important role in the body’s daily rhythms. The latest studies indicate that appropriately timed light exposure reduces melatonin “overshoot” into the early morning hours that might make people susceptible to depression.

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Wouldn’t more outside light benefit me as much as a light box could?

Some people who live and work in dim environments may feel a mildly perceptible improvement with increased exposure to outdoor light. Most people who experience depression, however, require much stronger intensities to feel any benefits. Also, it is important to note that light therapy has been proven to be most therapeutic in the early morning when outdoor daylight often is unavailable.

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I have recently been diagnosed with SAD and am about to purchase a light box. Both Medicaid and Medicare have refused to contribute toward its cost. I am wondering if you have any suggestions on what my doctors and I can do to change their minds.

Challenges with Reimbursement

We have heard of such reimbursements only rarely. The basic problem has been FDA’s long-standing disinclination to review the treatment method. Thus, insurers can dismiss it as “investigational,” rather than approved. The lack of FDA consideration is partly due to the failure of manufacturers to apply for pre-market approval, which entails significant cost (as is easily paid by the pharmaceutical industry, but not by small light box companies). It is also sometimes argued that such approval would restrict the technology to the prescription market, eliminating direct access by consumers.

Hope for Reimbursement in Future…

Meanwhile, there are several published consensus reports from professional organizations endorsing light therapy for SAD, and a strong statement is pending in the American Journal of Psychiatry. Increasingly, private insurers reimburse patients for the cost of light therapy apparatuses, given physician endorsement of reimbursement requests with appropriate DSM-IV diagnostic codes, e.g., 296.3 with seasonal pattern.

But not Now

We suspect that direct battle with Medicaid (or Medicare) will not succeed at this point, although protest by physicians might possibly catch the attention of government staff, and some constructive dialogue might ensue. Hope this information helps, even though we are pessimistic about your receiving coverage at this point.

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The CET Store offers two different light boxes, one of which uses a color temperature of 6500 Kelvin and the other, 4000 Kelvin. Also, one produces 7500 lux light intensity, and the other, 10,000 lux. Do these two units have different effectiveness, results, and purposes? How do I decide which would be better for me?

Before we answer, please note that last year’s (2003) model of the 10,000 lux device used lamps with 3000 Kelvin color temperature, which is perceptually a bit pinkish relative to the current 4000 Kelvin. Higher Kelvin does not necessarily translate into higher light dose, however. Both of our recommended units have been demonstrated to have antidepressant efficacy, although formal clinical trials for SAD have yet to be performed for the 7500 lux model.

The 7500 lux device was originally designed for enhanced work station lighting, to be flexibly used throughout the day at either low, medium or full intensity. This device has now also been positively evaluated at full intensity in patients with non-seasonal antepartum or bipolar depression, and there is no reason to think that it would not also work for SAD.

With lower maximum light output, some people will find that they need to increase exposure duration beyond the 30-minute average used with the 10,000 lux device. In antepartum depression studies, for example, patients used the 7500 lux device for 45-75 minutes; in a past SAD trial with another device providing about 7500 lux, everyone was treated for 90 minutes per day.

Because the manufacturers of these devices have chosen to use different color temperatures, however, it is impossible strictly to compare lux levels. All other things being equal, 6500 Kelvin appears whiter and brighter, while 4000 Kelvin appears softer. Both contain wavelengths that are active in the therapeutic range. We have named the 10,000 lux device a “clinical” unit, mainly because it has been extensively formally tested in clinical trials of SAD and chronic depression.

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Having been diagnosed with adult attention deficit disorder (ADD) and depression, I have been on medication for both but feel worse during the winter months. Are there any medications that would prevent me from tolerating the light? Also, in addition to fighting insomnia, I also find that I am unable to settle down at a reasonable hour, always moving, moving, moving, night after night. I read some people become energized by light therapy. Is this something I should be concerned with? Or is this a healthier energy than the one I experience and therefore worth trying?

Light therapy can be helpful for wintertime flare-ups of ADD and depression. If you use a 10,000 lux light box that strictly filters out ultraviolet light and attenuates blue — see our recommendation at the CET Store, — no problems are anticipated using concomitant prescription medications. (Still, you should watch out for unexpected side effects.) Yes, indeed, the energy enhancement from light therapy will be healthier than the agitation of ADD!!

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I have been suffering from chronic insomnia for several years. I have seen every doctor and tried every medication (both prescription and herb) imaginable and even spent the night in a sleep clinic, where they found no physical reasons for my sleep problem. My problem is that I can fall asleep just fine but then I awaken 2-3 hours later and never really fall back to sleep. I notice that when I do awaken after 2 hours, I am very hot and it takes me several hours to cool down. Once I do cool down, I am in and out of sleep (if I am lucky) for the rest of the night — changing blankets, going to the bathroom, etc. Do you have any thoughts about light therapy or any other suggestions?

This is a very specific question, but it raises general issues that will interest everyone. Your sleep quality and duration might improve if you adopted a later bedtime and built up more pressure to sleep. If you cannot stay awake for a later bedtime, late-evening bright light therapy might help. (Note that this is opposite to the time of day used for antidepressant treatment.) As for sleep meds, sometimes they begin to work only after you have restricted your sleep interval with later bedtime. Your problem may have been behaviorally conditioned over the years, now sustained primarily by the expectation for, and fear of early awakening. Try removing the clock as a stimulus: set the alarm and turn the clock away so that you can’t check it to verify that you are waking up after two hours. As for your heat sensations, sometimes this is the result, rather than the cause of early waking. If you are certain that you are warming up before you wake up, possibly try an aspirin at bedtime, which could serve to lower body temperature.

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What is sundowning, and what symptoms occur with this? Is light therapy something that should be considered? The individual is suffering from depression, irritablility and abnormal sleep patterns.

Sundowning refers to agitated, often disruptive behavior during a regular period each afternoon or evening, seen in some elderly patients with dementia. Patients with dementia also often show the other symptoms you mention. Although the research literature is divided on whether light therapy would alleviate symptoms, we think a standard schedule of morning light therapy is well worth a try. An issue is compliance — that is, will the patient with dementia sit for a light therapy session? In most cases, sessions will have to be monitored and supervised by an aide or family member. Since it is possible that light therapy will not be tolerated by the patient, the procedure should be undertaken only with a doctor’s guidance.

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Have you been able to determine how many kilowatts the 10,000 lux device uses? Specifically, how much electrical cost will daily 30-minute usage add to my electric bill?

Our engineering consultant advises: Most 10,000 lux systems with diffusion covers use about 125 watts / 120 volts of energy for a 30-minute exposure, or 0.125 of one kilowatt (=1000 watts) per session. So, math follows, 0.062 kilowatt/hour (kwh) per treatment. In other words, 1 kwh would covers 16 sessions and 2 kwh would get you through the month’s billing period. If you’re paying 7 cents per kwh, the total cost would be 14 cents. Not bad, eh?!

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For a long time now I have realized that I am not able to remain active at all without natural light. As long as I am outside, my energy level is great; however, as soon as I enter my house, my energy level is down by 80%. I have to push myself just to take care of daily chores. For years, I have known that some people need daylight just to function. I am not quite that bad; however, I do think I need daylight. Do I need light just in the evening hours when I am inside? Or do I need the morning and night light?

This is a clever and poignant question. It is possible that what you lack specifically is adequate early-morning light exposure, close to the time specified by CET’s Automated Morningness-Eveningness Questionnaire. Such light readjusts the internal biological clock which controls energy cycles. If that is the answer, light later in the day would be a secondary factor, possibly even irrelevant. However, bright light exposure can also exert a direct energizing effect, no matter what time of day (or night) it is received. “Better than coffee,” as one patient called it. If that is the answer, you might benefit by installing a light therapy apparatus at your desk at work, turning up the level whenever you start to slump. See CET’s recommended DaylightXL, at //, which was designed primarily for that purpose.

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Is there a particular type of light bulb which I can use in my rooms that would give out better lighting than what I am currently using (regular standard bulbs)? The lighting is very, very dim.

There are lots of ways to increase interior light level. The important considerations are two-fold: (1) You must ensure that the light is diffuse — or indirect — so you are not exposed to naked bulbs, whether they are standard incandescent, halogen or fluorescent. (2) You should be able to dim the light level, because you will not need or want the highest levels all the time. We recommend the simple, inexpensive halogen floor lamp shown on the CET Store page at for use in conjunction with our dawn/dusk simulator. (Note: the CET Store does not sell this lamp directly, but offers a link to an independent, low-cost supplier.)

For your application, you would not be using the simulator, just the floor lamp with its own dimmer. This lamp is particularly nice because it projects diffuse, bright light both upward and downward, at angles you can adjust, thus getting more total light to your eyes. A second, modern alternative at similar price is CET’s DaylightXL light box, which mimics a window to the bright outdoors. In the present application, you would not be sitting up close to XL — as is done for light therapy — but using it instead for whole-room illumination. (Sales of the XL do benefit CET.)

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10,000 lux at a distance of 12 inches from the light box screen has become a widely used measurement standard in the field of light therapy. A light box rated at 10,000 lux at a distance of 12 inches mimics the brightness of a window view on a sunlit scene. This is the white-light level that provides the most efficient treatment available for a session 30 minutes long. The combination of 10,000 lux / 30 minutes works for the large majority of light therapy users, although some will do best with lower lux, different durations, or both. (Higher lux has not been tested and should be avoided.) If a fixture rated 10,000 lux at 12 inches is placed at a comfortable arm’s length distance about 24 inches from the eyes (twice the 12 inch standard), the eyes will receive only one quarter the brightness, or about 2500 lux. To compensate, the session should be longer than 30 minutes.

As examples: if the eye receives 7000 lux, a user may need 45 minutes; or at 2500 lux, 1-2 hours. Carefully understand that we have stated “may” need extra time. These average times do not necessarily apply to any given individual. For example, some particularly light-sensitive people may find 30 minutes (or even less) at 5000 lux fully adequate. Each person is different and must determine aspects of their personal bright light regimen, including adequate length of light exposure, the best placement of the fixture at a comfortable distance and the best time of day to use the lights. (For initial time-of-day recommendations, complete the Automated Morningness-Eveningness Questionnaire at The combination of all these factors must be taken into account for a positive response to the lighting regimen – and you can expect to find the right solution in about 10 days of use.

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Several of my siblings suffered with severe cases of infectious mononucleosis. They all experienced delayed sleep phase, but this symptom of mono seems to be absent from the medical literature! My siblings recovered normal sleep habits after their bouts with mono, but for myself, the delayed sleep phase problem has become chronic. Any comments and suggestions

Hypersomnia — abnormally long sleep — is common during the active phase of bacterial and viral infections. Delayed sleep phase is another matter: sleep duration is normal, or somewhat longer than normal, but both sleep onset and wake-up times are significantly later than normal. In such cases, light therapy starting at spontaneous (late) wake-up time, and edging earlier over days, may help to alleviate the sleep problem and also increase daytime energy. Once the infection has passed — as you have described for yourself — the prognosis of normalized sleep timing with light therapy is excellent. One caveat: during the active period of infection, the eyes may become hypersensitive to bright light, making the treatment difficult to tolerate. In such cases, dawn simulation may be the answer, but this has yet to be tested.

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My daughter has been diagnosed with SAD and has purchased a light box which is helping her with waking and sleeping. She is 22 years old. Since she was about 10 years old, she has slept in the basement in a room without any windows. She has always had great difficulty waking up in the morning and going to sleep at night. Could sleeping in a room without natural light have had an impact on her sleep cycle?

Amen and amen. Our bodies have a physiological NEED to receive natural (or appropriate artificial) light early in the morning in order to stay in sync with external day and night. Dark basement conditions provide an environment conducive to developing and maintaining delayed sleep phase disorder (DSPD). This is often correctible with light therapy. We have long wanted to prepare a website section with a detailed discussion of DSPD and guidelines for how to rectify it. However, this will require additional visitor support. Please remember, contributions to CET–see the “Donate” page at–are tax-deductible under IRS 501(c)(3).

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I have a problem with chronic insomnia. I tire later and later each night, then sleep in later and later each morning, until I hit a wall and stay up for 24 hours straight. Then the cycle starts all over. I’ve tried getting up early so that I’ll tire earlier, but it doesn’t work; nor does getting up at the same time every morning. No matter how early I get up or how tired I feel all day, by night-time I’m raring to go! And if I try to go to bed eight hours before the time I want to awaken in the morning, I’ll just lie in bed. I finally will get up and tinker around until the wee hours of the morning. Right now it’s 3:30 a.m. and I’m online reading about insomnia…. What’s wrong with me?!!!

Two Sleep Phase Disorders in One

You are certainly not alone with this major problem! There are elements of two interrelated, well-described circadian sleep phase disorders at play. The first is delayed sleep phase disorder (DSPD), which occurs when a person cannot fall asleep until the wee hours despite all behavioral attempts and use of sleeping pills. The second is the “non-24-hour-sleep-wake-disorder,” in which bedtime drifts later and later–even around the clock. Your specific case has also been described previously: drifting later and later, suddenly resetting, and then drifting later and later again. The most likely cause is that your internal physiological clock runs substantially slower than on a 24-hour cycle–most probably, an inherited genetic characteristic–and this clock is effectively (and unfortunately) fighting a winning battle with the outdoor day-night cycle.

Possible Solutions

The problem is potentially correctable by sensitively-timed bright light therapy, which would begin around the time you are currently waking up. That might arrest the drift later, after which you could edge the light timing earlier in small steps to normalize your sleep period. It would be easiest to begin doing this right after you have “reset” to an earlier hour after drifting late. Practically speaking, you may need the supervision of an experienced clinician, who might combine other methods to reinforce the light therapy. As we noted in our answer to question #3093, we have long wanted to prepare a website section with a detailed discussion of DSPD [and Non-24-Hour-Sleep-Wake Disorder] and with structured guidelines for how to rectify them. However, this will require additional visitor support. One can earmark contributions toward this project, which we will keep in a dedicated account. For further information, please see the Donate page at

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Two basic answers: (1) Start by using your light box when you do finally get up, even if that is late. This will have the effect of making it easier to rise earlier. Every few days, advance the time of your light therapy sessions earlier by 15 minutes (or 30 minutes, if you suddenly begin waking up substantially earlier). Before long, you should be able to wake up at 7:00 a.m. without effort. (2) Out of concern for your welfare, perhaps your partner would agree to wear a sleep mask so you could gain the advantage of dawn simulation. The major reason you cannot get up earlier, no matter when you go to sleep, is that the internal circadian rhythm clock in your brain is not producing its wake-up signal until later. The essence of morning light therapy lies in resetting the internal clock earlier.

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I have been treated for major depression and bipolar disorder for several years, with different medications, but with no significant relief! Recently, I purchased a light box, but after six days I have had no positive relief. Does light therapy have a different time frame for positive results on different people and different clinical depressions? Will it take longer for me to see an improvement in my mood because of my specific condition? Should I increase my duration of treatment from 30 to 45 or 60 minutes in the early a.m.?

Don’t Self-Treat

First of all, we do not recommend self-treatment of major depression or bipolar disorder. There are too many interacting factors that need to be sorted out by a clinician–and although it is possible that you will experience improvement without such guidance and monitoring, if you don’t, you are not in the best position to decide next steps on your own. We can generalize about some factors that might be operating in your situation, however. Patients with bipolar disorder should use light therapy only after establishing a steady dose of a mood-stabilizing drug (examples: lithium, Depakote). Otherwise, they are vulnerable to sudden switching between extreme mood states, sometimes with rapid cycling, which can be extremely distressing. Some patients with bipolar disorder have responded preferentially to light therapy at midday rather than early morning, which is a milder treatment strategy-one which most patients with SAD do not require.

Personal Variations in Treatment

Research suggests that patients with non-seasonal depression respond more gradually to light therapy than do patients with SAD, and the clear onset of positive effect may not be apparent for several weeks. In one study of non-seasonal patients with chronic, major depression, light duration was standardized at 60 minutes at 10,000 lux, while in another study of non-seasonal bipolar disorder, very short exposures (15 minutes) appeared optimal. Some patients with non-seasonal depression respond adequately to a combination of light therapy and antidepressant drugs, while either one alone is insufficient. We hope you see why clinical management may be very important for you.

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How do you respond to the following critique of negative air ion therapy: “…there is no practical way of controlling the ion concentration, which varies with room size, ventilation, machine capacity, and other factors. Therefore, using an ion generator is like taking an unknown dose of a medicine that has unknown effects,” by nutritionist Kurt Butler in A Consumer’s Guide to Alternative Medicine.

This is an excellent point: we do not have precise control of ion dosage. All we really know is the ion flow rate of the generator; all the other factors you list will modulate what the person actually receives (the “dose”). CET’s recommended apparatus was designed to maximize flow to the subject — and thus reduce dose variability — by addition of a grounded wrist strap. The vagaries of dosing aside, however, there are important reasons to seriously consider this new treatment modality:

First, ion generators with high flow rate in close proximity to the subject have produced significant antidepressant results relative to low flow rates. Second, the treatment appears to be innocuous — not only is ion “dose” imperceptible,–no disturbing side effects have been found thus far in controlled clinical trials. To generalize a bit further, consider that a standard “dose” of medication taken in pill form will result in vastly different blood (and brain) concentrations from person to person. Same thing with light therapy: when we measure how many lux a person receives at a light box, it varies significantly between people and indeed within a session for each person.

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I am considering using a light box to adjust my circadian rhythm, which is now severely delayed. I live in an apartment with large windows providing lots of daylight. At night, a nearby parking lot provides some light through my blinds. I recently bought a large sleep mask, as putting up blackout curtains could create problems with my landlord. Is my approach reasonable, or totally illogical?

To correct delayed sleep phase, there are two principles and procedures to keep in mind: (1) Restrict light exposure as much as possible in the evening and at night until about 1.5 hours before wake-up time. (If your wake-up time is in the mid- to late morning, minimizing light exposure will be important throughout early morning.) Before sleep, you want to turn down the lights to a comfortable level for reading or watching TV, but nothing more. During sleep, even low levels of light can be counterproductive, so consider adding dark curtains inside your blinds to block light from the parking lot. (2) Starting at wake-up time, or 1.5 hours earlier, you want to enhance light exposure to counteract your delayed rhythm. Since your bedroom will be dark, you cannot utilize light through the windows.

There are two complementary solutions: First, you can use a dawn simulator for 90 minutes before wake-up time, or simply an appliance timer to turn on bedroom lights. Second, 30 to 60 minutes of bright light box therapy will be helpful when you wake up–a good time for breakfast and reading the newspaper. Over a couple of weeks, move your wake-up time (and light exposure) gradually earlier–say, 15 minutes every three days. Before long, you can expect to normalize your delayed pattern.

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Do you agree with the opinion that SAD should be treated simultaneously by light, regularly scheduled exercise and proper diet? Or do you believe light treatment alone is enough? Just how important is regular exercise during the winter months?

Aerobic exercise can indeed complement the antidepressant and energizing effect of light therapy. Problem is, many people suffering depression cannot garner the motivation to maintain a regular exercise regimen. We suggest first starting with bright light therapy, and as its beneficial effect sets in, taking the opportunity to begin a daily aerobic routine. As for diet, regular healthy measures are all we would suggest. Once the antidepressant effect from light (or light + exercise) sets in, it becomes far easier to control excessive carb intake.

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I just began using my light box a little more than a week ago. Since that time the following has occurred: (1) I get a lightheaded feeling with a tingling sensation in my hands/fingers. Sometimes I also get nauseous. This could last up to a few hours. (2) I fell down an entire flight of stairs on the third day. It was as though my perception was off. (3) My whole sleep pattern has changed. I would normally go to bed around 10 p.m. and wake around 6 a.m. Since using the light, I go to sleep at around 11 p.m. and wake around 4 a.m. (4) It feels like I have entered into a manic state — is that possible?

Light overdose can indeed induce the symptoms you describe. If you have been using a blue light box, you should stop using it immediately. If you have a history of bipolar disorder, you should not use light therapy without first establishing a prescribed mood stabilizing drug. Even then, you should remain under a doctor’s care and supervision. If this is the first time you have felt “manicky,” you should terminate treatment for several days, and then attempt it only with a shorter duration (say, 15 rather than 30 minutes), sitting 6 inches further back from the screen, and scheduling it later in the morning. If symptoms recur, you should not proceed without professional supervision.

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This may sound strange: Is there an opposite disorder to SAD where sunlight actually depresses you? I’ve struggled with sunlight for about 10 years, but have had no skin reaction, other than a melanoma a couple of years ago. I really have a hard time getting through sunny days in a normal manner. It is amazing how wonderful my days are when it is overcast outside.

This is an unusual report, but there are some possible explanations. Some people experience “photophobia”–with very disruptive reactions to bright light exposure, which may be related to hypersensitivity of the retina of the eye, psychological factors, or both. If you use a photosensitizing medication, that may be responsible. There have been scattered reports of people becoming very sleepy during and after bright light exposure; it is not clear whether this is due to the time of day of light exposure. Possibly, your reaction to outdoor sunlight is triggered by the strong blue component of white light. If so, you may benefit by using blue-blocking wrap-around glasses, such as Model 58 from Finally, you may be suffering from summer depression, which is more plausibly related to high heat and humidity than bright light.

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My ideal timing for light therapy, according to your Automated Morningness-Eveningness Questionnaire, is 6:45 a.m. Now, in my country, daylight starts sooner than that time. When daylight starts sooner, is light therapy in the morning neccessary anymore? When should I stop? The days are getting longer and longer. Step by step, I’m feeling better and getting out of severe problems. Thank you very much for your advice in this forum.

Good thinking. If you’re feeling better, and if you receive the sunrise signal in your bedroom, it makes sense to try discontinuing treatment. If you slump, you can always resume treatment for a few more weeks, and then try quitting again. You do not mention where you live, but the experience of patients who live around 40 degrees North latitude is that untreated SAD symptoms do not remit spontaneously until early May. Therefore, most patients prefer to continue light therapy throughout April and not risk slumping or relapse. Your situation may be different, of course.

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Living in upper New York State with low winter daylight, I wonder if flooding the house with overhead bright light to simulate overhead sunshine would be of any benefit. I mean to make it as bright as a sunny day outside, inside the entire house. I’m sure our electric bill would rise, but leaving our home would be an extreme solution. I have noticed a pattern of winter anxiety in my daughter for four years now (she’s 10) and I know I can deal with my SAD, but if I can change it for her, I want to. We have taken extended winter vacations south and everyone sees benefits. Would a move be better in the long run? Thanks for supplying this forum. There are many interesting questions and answers. It is very informative

Your proposal, we have to say, is well-intentioned but impractical as well as unnecessary. Instrumenting overhead lighting at full daylight intensity has been done only in a few research laboratories, at great expense, including for dedicated high-power air conditioning to expel the high heat load. It makes more sense to follow established winter light therapy regimens, which focus illumination on the final period of sleep or the period immediately following wake-up. Almost always, that is sufficient to allay winter symptoms.

We suggest completing our Morningness-Eveningness Questionnaire, and scheduling restricted light exposure accordingly. Kids may find dawn simulation most acceptable, since it is automated in the bedroom and requires no daytime behavioral compliance. If your family is contemplating a move south, before making the commitment we recommend testing one winter at your selected destination to make sure it does the trick. Some people are disappointed to find that winter depression can follow them down south, even though days are relatively longer than in the north

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For all of my adult life (I’m 40), my sleep/wake schedule has been very inconsistent, mostly because I sleep late when I can do so and don’t get into bed until I feel very sleepy. I recognize that regulating my bedtime and wake times would probably have some benefits, such as increased energy at predictable times and easier wakenings. Am I correct in this assumption–and if I am, how does a person go about “deciding” when to go to bed and wake, and ensuring that they stay regular in this.

There is a hint in what you write that you are inherently a “late chronotype”–that if you did not have morning obligations, you would go to sleep late and wake up late. To find out whether that is your natural physiological tendency, take the Automated Morningness-Eveningess Questionnaire (AutoMEQ) on The AutoMEQ tells you when your natural bedtime would be according to your internal circadian clock. You are correct in guessing that regular bedtime and rise time is the healthy strategy, but you are incorrect in assuming that simply making a decision about an earlier bedtime and rise time will do the trick. To be effective–to fall asleep when you are sleepy–you need to time your sleep to synchronize with your internal circadian clock. If your clock is running late, you may want to adjust it earlier with morning light therapy, and the AutoMEQ will advise you how.

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My goals are to regularize my sleep-wake cycle and treat some mild but persistent depression. At your suggestion, I took your Automated Morningness-Eveningness Questionnaire (AutoMEQ). It indicates that my natural bedtime is at approximately 12:15 a.m. and it recommends that I begin light therapy at 7:00 a.m. This would allow for 6 3/4 hours of sleep, which almost always feels like too little sleep for me–I usually need about 8 to 8 1/2 hours of sleep to function reasonably well. Bearing all of this in mind, could I go to sleep sooner than 12:15 a.m. if I feel sleepy? Or should I try to stick to the 12:15 a.m. to 7:00 a.m. schedule proposed in the AutoMEQ?

We give two perspectives in our answer: (1) Some people with depression sleep significantly longer than when they are feeling well. Therefore, if you respond to light therapy at 7:00 a.m., you may find that 6 3/4 hours of sleep is surprisingly refreshing and adequate. (2) Because the light therapy schedule is designed to shift your internal circadian clock earlier, it is quite possible that you will begin to get sleepy before 12:15 a.m. Go to sleep when that feeling sets in–don’t force yourself up until 12:15 a.m. You may thereby partially or even totally compensate for any sleep loss during light treatment. The AutoMEQ does not assign bedtime, it just tells you when your circadian clock is ready to initiate sleep BEFORE you start light therapy. Follow your nose, and you will find the best bedtime after treatment at 7:00 a.m. begins

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I think I have delayed sleep phase disorder (DSPD). I took the Automated Morningness-Eveningness Questionnaire and got some interesting suggestions I’d like to try. Even when I get sleepy in the evening, I tend to stay up for an hour or two or three, and then the next thing I know, it is 1:45 a.m. (or 2:45 a.m.) and I have an alarm set for 7:30 a.m. I’ve tried taking melatonin and Benadryl, but they don’t have any effect. If I fall asleep so easily, the question of why don’t I just get into bed at a “reasonable” hour is one that plagues me. I just can’t seem to change the habit, even though I really want to. I’m going to try setting a light on a timer next to my bed at the survey’s recommended time of 6:45 a.m. But with my additional habit of pushing past my sleepiness in the evening, will this help?

Definitely worth a try, since by resetting your internal clock earlier with the light, you are less likely to want to stay up late. Keep in mind, though, that the intensity of the light you use at 6:45 a.m. is an important factor that may require adjustment during your trial. Although ordinary bedroom lamps might work for you, they might be insufficient.

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It is mainly thanks to CET’s website that I have been self-treating with a light box for delayed sleep phase disorder (DSPD) over the last six years. I can really see that it is a powerful treatment, far more effective than everything else I have tried–and I tried many, many things over the years, from diet alterations to sleeping tablets to Chinese medicine and much more. Although the light treatment works, I still find it difficult to stick to a “normal” schedule. A few times I have failed to force myself to get up to use the lights in the morning (especially on the weekend it takes a lot of willpower) and I’ve found that the consequences of just delaying the treatment even by an hour or so for one day are that it takes three or four days of using the lights correctly in order to get back on track. Are there any tips or tricks to help avoid this happening, or to help me resynchronize faster if it does happen? In your experience, do you find that long-term DSPD sufferers eventually “unlearn” these habits and find it easier over time to stick to a regular schedule, or will it always require as much willpower and self-discipline as it does for me.

This is a great, insightful contribution to our forum. Some thoughts in response: If you are finding it difficult to wake up on schedule, it’s a sign of that you have gained only partial effect. We want it to become easy to wake up at the target time. You might achieve this by increasing your light dose with higher lux (but please, not above 10,000 lux) or longer session duration. If the session gets as long as an hour, take a brief break in the middle for some stretching. Second idea: Short of using a dawn simulator, attach your bed lamp to an electronic appliance timer set for 15 minutes before wake-up, and then proceed to the bright light session. If you find the bedside light disturbing, stop using it. Third idea: Take a low-dose melatonin capsule (not more than 1 mg) in the evening 12 hours before the scheduled light session. This should reinforce the phase-shifting effect of morning light without making you sleepy immediately. Thus, you’ll go to sleep about four hours after taking the melatonin if you are an eight-hour sleeper. If the melatonin disturbs your sleep, stop using it. You are correct: once you slip later, you should not resume the lights at the target time, but rather edge earlier over several days from when you are waking up. Finally, during the four hours before bedtime, keep your room lights low-–just comfortable enough for reading, socializing and watching TV–and avoid exercise and stimulating work activities that can contribute to difficult sleep onset.

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I suffer from delayed sleep phase disorder (DSPD) and for years have been using a bright light and radio on a timer to wake up. Also, after I started following Ask the Doctor on, I became much more careful to use dim lights closer to bedtime. These have both been very helpful. (I am also using CET’s ionizer, and although it doesn’t seem to affect my DSPD, it has greatly reduced the chronic congestion I’d been suffering–my wife reports that it has almost completely eliminated my snoring.) Additionally, I have been using melatonin occasionally, but when I use it I take it right when I’m going to bed (usually 6-7 hours before my projected wake time) or if I wake up an hour or two later and am tossing and turning. So I read with interest your recommendation to take melatonin 12 hours prior to wake time. Am I potentially doing more harm than good taking it later than that?

The reason for the earlier melatonin dose is that it reinforces the action of the light in setting your internal clock earlier, thereby making it easier to wake up. This use of melatonin is not as a sleep aid, and for that reason you should use a very low dose (not more than 1 mg) that will not make you sleepy before your bedtime. The potential problem using melatonin when you wake up at night is that it may stay in the bloodstream after wake-up time, contributing to difficulty waking and morning grogginess.

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I’m in the midst of a chronobiologic Catch-22: I need to wake up earlier to use my light box (for depression) and to get to work on time, but when I set my alarm for the time suggested by the AutoMEQ (and my boss!), I’m not able to wake up and in fact I’m so deeply asleep that I sleep for another hour despite the alarm blaring away. Each night I tell myself that I’ll force myself out of bed the next morning at the necessary time, but when the alarm goes off, I don’t even become conscious enough to act on that resolution. How can I wake up early enough? I try going to bed earlier but, even though I dim the lights in the evening, I’m not able to fall asleep sooner than my usual time. Thanks for the help.

It won’t work immediately to wake up at your target time. You need to start using the lights about 15-30 minutes before your normal (late) wake-up time, which will start to move your internal clock earlier. Every few days, you can advance your wake-up/light time by 15-30 minutes, depending on how early you can wake up easily. Over a period of time–which might last two weeks, for example–you will be able to approach your target (early) wake-up time. This cannot be done abruptly! If you have difficulty even with the small adjustments earlier, try low-dose melatonin (0.3 to 1.0 mg) 12 hours before your current wake-up time. As you move wake-up and lights earlier, also move the melatonin earlier.

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I’m using a light box (10,000 lux) for 30 minutes at 7:30 each morning for depression and to help me get up at a reasonable hour. Initially, 30 minutes of light worked very well but now it doesn’t seem to help as much––I don’t get that same sense of energy and well-being. I live in the mid-western USA and it’s early summer here. Should I extend the duration of my light exposure in the morning? Do people develop a tolerance to light therapy in the same way they do to some drugs? Thanks.

Tolerance, in the same sense as for drugs, is not a problem with light therapy. However, dose adjustments (intensity, exposure duration, and timing) are sometimes needed. Think about outdoor lighting conditions in the summer. (We’re answering this question on June 21, the summer solstice, when the length of daylight is the longest of the year!) There is much more evening light preceding your bedtime, which can have the effect of delaying your internal circadian clock and making it harder to wake up in the morning. There is also much more morning light, which begins well before your wake-up time at 7:30 a.m.

If 7:30 a.m. remains your target, make sure you restrict evening light exposure as much as possible, by using dark sunglasses outdoors and keeping indoor light as low as possible while remaining comfortable for reading, etc. If that doesn’t do the trick, also use a 45 minute light exposure at 7:15 a.m. And if that combination doesn’t work, add a very low dose of melatonin (0.1 mg) 12 hours before you use the lights (for example, 7:15 p.m.). It would also be wise to complete our Automated Morningness-Eveningness Questionnaire at for a summertime assessment, since the recommended time for light therapy can change with the seasons.

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Is it possible to have a rare case of extreme advance of sleep, which means you get tired, earlier and earlier in the day, but without depression? It is actually the opposite of delay phase. The condition was caused by seeing light at the wrong time of the day, causing a phase advance, repeated again and again, leading to a very bad situation–really early sleep onset morning/afternoon with insomnia at night. Do you have suggestions to correct this rare case?

Yes, the advanced sleep phase syndrome is opposite to the more prevalent delayed sleep phase syndrome. This may be caused by inappropriate light exposure, a genetic predisposition for a fast internal circadian clock, or both. You indicate that before your repeated light exposure at the “wrong time of day” you did not experience the problem, so the cause appears to be environmental. Yet, it seems that the problem did not resolve after you eliminated the problematic lighting exposure. We would need to know much more about your abnormal sleep, and also your work schedule, in order to make a specific recommendation (which is beyond the scope of this forum).

However, we can offer some general hints. Using bright light therapy just before your daytime sleep episode (say, noontime), followed by restricted light exposure (strong wrap-around sunglasses) for the rest of the day after you wake up, should begin to move your internal clock later. As this happens, you can delay the light exposure accordingly, until you are going to sleep in the late evening (say, 10 p.m.). You can expedite the process by taking a low dose of melatonin (say, 3 mg) when you wake up in late afternoon or early evening. Be careful never to use melatonin when exposed to bright outdoor or indoor light. Caveat: If you are getting significant sleep at night, beyond your daytime sleep, the solution would require clinical consultation with a sleep clinician.

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For use with a light box (with or without UV shielding), is it better to buy UV glasses to block possible UV rays entering the eye?

It is unnecessary to add UV glasses when using a light box that has filtered out UV at the 99%+ level. Tinted UV glasses will actually reduce the level of therapeutic light you receive. That said, however, some light box manufacturers claim to filter out UV when in fact their devices fall short of the 99%+ level. In such cases, clear UV glasses would protect the eyes, but not the skin. In our experience, the only screens that do the job perfectly use polycarbonate or OP-3 diffusers. Check manufacturers’ specs!

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Do most people respond to light therapy even at the “right time” for phase advances or delays? Does it need to be done at late night or early morning when it is dark?

The circadian rhythm system is most responsive to light–producing phase shifts–when it is done therapeutically at the edges of a person’s “subjective night.” What is subjective night? It’s not the same thing as night outdoors. People vary by as much as six hours (early types, late types; larks, owls) in their subjective night. How can you find out about your subjective night and the specific time that morning light therapy is expected to work best for you (by phase advancing your internal clock)? Complete our Automated Morningness-Eveningness Questionnaire at, and you’ll find the answer.

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What does spectrum mean when talking about light therapy? Is “sunlight” a type of spectrum for the lamp or just like sunlight outdoors. Does the spectrum matter? Thanks for your advice.

Any light source (the sun, lamps, candles, even fireflies!) produces visible energy of different wavelengths. When we use a narrow-spectrum lamp that produces a very narrow range of wavelengths, we see a pure color (red, green, blue, yellow, etc.). When a lamp mixes wavelengths across the visible spectrum, our sensation of color is reduced–we may see white, or pinkish white, or bluish white, etc. The sun, as well as incandescent lamps and fluorescent lamps, all mix wavelengths in different ways. It is incorrect to call any lamp a “sunlight lamp,”, because no lamp matches the sun’s wavelength spectrum. Any manufacturer who claims to provide a sunlight lamp is deceiving customers, and should not be trusted.

For light therapy, we recommend fluorescent light boxes that present a broad spectrum of wavelengths, yielding whitish light at high intensity (10,000 lux) while minimizing aversive visual glare. In order to do this, short visible wavelengths in the blue range need to be present, but they should not be emphasized for several reasons: they produce aversive glare, they can interact with medications to be harmful to the eyes, and over years of exposure they can directly harm the eyes and contribute to reduced vision in old age. In our judgment, the best spectral balance for light therapy is provided by white-light lamps of 3000-5000 Kelvin color temperature, not higher or lower. We recommend not using colored lights or “full spectrum” white light above 5000 Kelvin. For further information, see our store at

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Who are the people advertising under the name, “The Light Therapy Institute?” They say, “Studies have shown that bright light therapy can prove beneficial for jet lag, shift work, insomnia.” Is the statement just general or does it actually apply to the product they are selling? Is the claim valid? Do you need medical advice to successfully get results from light therapy–and what happens if there is no available medical advice where you live outside of America?

Very important questions for consumers living both inside and outside the U.S. First, it is grossly deceptive for a commercial light box supplier to name itself The Light Therapy Institute. They have no such clinical authority–it is an advertising trick aimed at gullible consumers. Second, although light therapy is now being used successfully to treat a specific circadian rhythm sleep disorder (delayed sleep phase syndrome) and its milder version (difficulty falling asleep and waking up on time), there are no such successfully validated applications for shift work and jet lag. Those remain active research areas–and we hope in a few years there will be tested recommendations for consumers. For now, it’s just advertising hype. Third, even in the U.S., it is still difficult to find a light therapy specialist for consultation. It is a high priority to educate doctors in this technology. New training materials are now available (as in the August 2005, Vol. 10, No. 8 issue of the journal CNS Spectrums, At present, most consumers will continue to rely on the kind of internet information we offer at

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I have read that one needs expert professional supervision to synchronize the time of light exposure to your body temperature for effective light therapy. Can you read your body temperature yourself, or is an expert totally necessary? Do you have any suggestions if no expert is available?

First of all, body temperature is NOT the best anchor for timing light therapy, since it is determined by many factors in addition to your internal circadian rhythm. In the laboratory, “core” body temperature is measured by a rectal thermometer that is worn continuously all day and night in order to determine the pattern–not very convenient for patients at home! Oral temperature does not provide an adequate measure. A far better indicator of the internal clock is the pattern of melatonin production by the pineal gland, which lies deep within the brain. Melatonin level can be measured in blood or saliva. However, that, too, is not practical for clinical purposes. To address this problem, CET developed the Automated Morningness-Eveningess Questionnaire (AutoMEQ), which is available free on our website, The AutoMEQ score closely reflects melatonin timing, and thus provides a circadian time anchor for light therapy.

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Do you have any suggestions for someone who has suffered with summer depression for years. Obviously the light box won’t work. I am helped with Paxil–but do wean myself off of it, and then the next summer, the depression starts all over. I have been bothered by summer depression since my teenage years. I live in the south on the Gulf of Mexico, where summer temperatures and humidity become unbearable.

You’re on the right course: the primary treatment for summer depression remains standard antidepressant drugs. You are smart to wean yourself off Paxil in the fall, but you should resume it in late spring in order to try to prevent the next summer’s relapse. Some people with summer depression find relief in strongly air conditioned environments (and, believe it or not, by taking frequent cold showers)–but these measures are temporary, and mood and energy can plummet as soon as you go outdoors. It is also worth testing whether heavily filtered wrap-around sunglasses provide relief, although this method has been used mainly by people who become “hyper” or agitated each summer.

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I have been tracking my migraines for years. I have clusters that go up in the winter and down in the summer. Jan.-Feb.-Mar.-Apr. are the worst, with headaches up to 70% of the days during those months. By May, they drop to 35% of the days. By summer, headaches are 1-4 a month. By the fall, I dread the return of winter and headaches as percentages begin to climb with shortening days. This has gone on for 15 years. Zomig is the only drug that helps but it is expensive. Nortryptiline does not help. Topomax does not help. Can light therapy help me?

Good question. Migraines have been related to reduced availability of brain serotonin in winter. The same story holds for winter depression. Many people with winter depression experience headache, which resolves with light therapy. However, others experience emergent headache as a side effect of light therapy, which is no fun. Migraines are often exacerbated by bright light exposure (which is one reason migraine sufferers often retreat to darkened bedrooms), and light therapy for migraine has never been tested in clinical trials. Bottom line: you can certainly test light therapy, but we cannot specifically advise it for this purpose.

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Is it true that for society in general, people have a mind of their own by disrespecting or not taking account of their circadian rhythms, especially in cases of undiagnosed, Delayed or Advanced Sleep Phase Disorder (DSPD, ASPS)?

Thank you for this provocative question. Surely, it is true that most people with DSPD and ASPS, although they realize their sleep is displaced relative to the norm, do not identify the situation as a “disorder” or attribute it to their circadian rhythms. Many of them accommodate it by making a circle of friends with similar sleep patterns (active phone calling after midnight, etc.) and finding jobs that do not require a 9-5 work schedule (bartending, acting, free-lance writing, etc.) Importantly, however, many also experience depression, and cannot maintain self-supporting employment or family life. Some, with partners who sleep normal hours, develop serious conflicts at home (even with the threat of divorce). When such problems develop, you will recognize that you have a serious problem, but still you are unlikely to attribute it to a circadian rhythm disturbance.

The Center for Environmental Therapeutics has a major goal of teaching people with ASPS and DSPD the nature of the problem and guiding them toward effective treatment and adjustment using the most potent method available–light therapy. Light therapy needs to be complemented with restricted lighting at other times of day in order to normalize the sleep pattern. In DSPD, for example, it is important to receive ample light exposure after sleep, but to minimize light exposure before sleep. The opposite holds for ASPS. People have achieved dramatic improvement using these simple techniques.

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I would like to know if there is a difference between a UV blocked full-spectrum and a broad-spectrum light box.

The terms “full spectrum” and “broad spectrum” are not precise technical terms. Full spectrum–which is really just an advertising term–was developed as a type of broad spectrum lamp that emphasized short-wavelength emission, including UV. “UV-blocked full spectrum” is therefore a contradiction in terms. Furthermore, UV-blocking is incomplete using cheap plastic diffuser screens, leaving the opportunity for skin reddening and puffiness (even burning) in people with sensitive skin. These lamps may also cause retinal photosensitization when used in combination with various drugs.

Broad spectrum lamps include all fluorescent lamps with a white or whitish appearance. They are differentiated by “color temperature”, as measured in Kelvins. Full spectrum lamps have very high color temperatures (5500 Kelvin and above), which cause considerable visual glare at the high intensities used therapeutically. They are also electrically inefficient and more expensive than alternatives. Broad spectrum lamps of 3000-4000 Kelvin are much easier on the eyes and are equally effective therapeutically. We specifically recommend 4000 Kelvin lamps with complete UV filtering, based on the most recent clinical tests at Columbia University. For people whose doctors have recommended reduced blue exposure, to allay age-related macular degeneration, we recommend 3000 Kelvin lamps.

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I am 50 years old and have struggled with insomnia for decades. I can even remember not being able to fall asleep as early as five years old. I have always found some way to cope with it even though I would be in a fog most of the time. I have noticed that in the past seven years it is getting out of control and it is constricting my life to the point that I am becoming house bound due to lack of sleep. Sleeping pills don’t touch it; alcohol seems to make it worse. I have tried not sleeping all day for days and to no avail; I end up without any sleep. I have adhered to all the sleep hygiene recommendations, but I can’t seem to fall asleep until 5:00 a.m., or when the sun comes up. Around 7:30 p.m., I take a short nap because I am exhausted, and I am averaging 4 to 5 hours of sleep a day. My room is darkened and I have a very loud fan going to obliterate all other sounds. I think I am going crazy, and no one I know has this problem. If I were to strictly adhere to scheduled use of a bright light, would it give me a sleep schedule that is somewhat normal?

You give lots of information about this difficult situation– ot enough to give a definitive answer, but plenty on which to speculate. First, you are not alone with this problem, which is typical of the delayed sleep phase disorder-in extremis– coupled with a fight to get to sleep on a normal nighttime schedule. As you say, the problem can be life-long, and it can get worse over time. In DSPD, sleeping pills don’t work because they don’t adjust the internal clock earlier, and several common sleep hygiene principles (for example, sleeping at night in a dark room) are irrelevant. One major question is whether, if you allowed yourself to sleep in a dark room during the day, you would have normal sleep duration. That’s an experiment–probably not a solution, assuming you are obligated to function during the day. Light therapy might provide a solution, but it will not work if you simply start doing it in the early morning (which, to you, is really early night).

A general strategy would be to: (a) find out when you awaken in the afternoon after you allow yourself to sleep during the day for several days; (b) begin light therapy at that hour; (c) gradually schedule light therapy (and wake-up) earlier over several weeks; (d) see if you become sleepy and can fall asleep gradually earlier at some point in this process. If it works, you can aim for wake-up when you are now falling asleep, which will need to be maintained by a daily schedule of morning light therapy. It may facilitate the transition to take a low dose of melatonin (1-3 mg) 12 hours before you use the lights–which means gradually, as you move the lights earlier. It may also be worth considering with your doctor the use of a new melatonin-like prescription drug, Rozerem, if you don’t find the melatonin helpful. Finally, keep room lights as low as possible and avoid work, physical activity, caffeine and heavy meals for at least five hours before you sleep. Obviously, you will not be able to keep a normal daytime work schedule during the transition period, so you will need a vacation or leave of absence of up to a month. We make all these suggestions on the assumption that you have DSPD; if the strategy works, you will validate the assumption. It would be best to proceed under monitoring and guidance of a sleep medicine specialist

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I am a 22-year-old female who has had chronic fatigue syndrome (CFS) for almost two years. During that time, my sleep has been awful. I’ve had difficulty falling asleep, staying asleep, have experienced severe body aches for hours on end, and awoken from 2-4 hours of unrefreshing sleep feeling worse than before. I dreaded bedtime and began taking melatonin supplements at night; I noticed immediate results. I can now generally get 6-8 hours of somewhat refreshing sleep at night, although the beginning and ending times are extremely variable (10:15pm – 2:00am start, 4:00am-9:30am end). I have never had any reason to suspect SAD before, but have noticed since the onset of CFS symptoms that I feel significantly worse on cloudy days. I am much more fatigued than other days, feel rather drab, cannot concentrate as well, and combat feelings of disappointment and sadness at times. I have noticed myself subconsciously staying near brightly lit places. I’m wondering if light therapy might be useful. I don’t want to take any more pills than I already am and don’t want to waste money for something unbeneficial. What’s your opinion?

We bet you have not seen CET President Michael Terman’s article with CFS expert Susan Levine: “Chronic fatigue syndrome and seasonal affective disorder: comorbidity, overlap, and implications for treatment.,” American Journal of Medicine 1998;105:115S-124S. It turns out that the hallmark symptoms of SAD occur just as frequently in patients with CFS. In a series of case studies, light therapy produced marked improvement. Patients with SAD also often slump during a string of dark, rainy summer days–and they find their light boxes as useful then as in winter. More importantly, we think, patients with CFS spend an inordinate amount of time indoors and in bed, creating an artificially darkened environment.

As we have learned from recent clinical trials of patients with non-seasonal depression, light therapy can work year-round. Indeed, long winter nights are just one of many ways we come to spend excessive time in the dark. Our advice is to follow the guidelines we offer on our website for light box selection and scheduling (take the Morningness-Eveningness Questionnaire). It would be best to do this under monitoring by your clinician, since if you show gains it may be possible to taper your medication regimen. If your clinician is inexperienced with or skeptical about lights, refer him or her to the August 2005 issue of the journal CNS Spectrums for a comprehensive review. One word about melatonin use inconjunction with light therapy: never employ the latter in the hours after taking melatonin, because it is a photosensitizer. As a general rule, schedule evening melatonin at low dose, 12 hours before you use the lights.

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My 16-year-old daughter is perpetually tired, even though she sleeps well and gets plenty of it. She goes to bed at 9 at night and gets up at 6 a.m., which is much more sleep than her peers get, and she is still tired–sometimes to the point of falling asleep in class. She struggles also with chronic colds/allergies/headaches that the doctor can’t seem to find a physiological basis or cure for. She can’t seem to manage any of the demanding extra curriculars her friends handle either, because when she’s tried them, she gets quickly fatigued and/or sick. Is there anything about using a light box that might help her?

The combination of physical symptoms and fatigue makes this sound like chronic fatigue syndrome (CFS), which can indeed be debilitating–for up to several years–before it resolves. There is a host of treatment approaches, but no definitive curing agent. You should begin with a work-up by a CFS specialist (check Light therapy has been very helpful for people with CFS who have trouble waking up in the morning, who feel depressed, and become too tired to go to school or work. It may be very useful as an adjunctive treatment in CFS, but it is not a first-line intervention for the disorder.

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Good sleep hygiene–which is especially important for people with depression–mandates a consistent wake-up time, even when you go to bed late. Indeed, “sleeping in” can exacerbate depressive symptoms. In the real world, though, people will sometimes not be able to meet their early target time for light exposure. Light therapy later in the morning is better than skipping it altogether, but you should never use light therapy earlier than the MEQ-recommended time unless directed to do so (and monitored) by a clinician. Increasing light duration later in the morning makes intuitive and logical sense, but this has never been tested in clinical trials. Very interesting idea, but you’ll have to follow your nose with that strategy, and remain vigilant about overdose side effects such as headache and agitation

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I have at least some degree of depression on a year-round basis with a worsening in the winter months. In the past, I’ve responded very well to treatment consisting of continuous antidepressant medication and the addition of light therapy in the winter. I’m about to start my light treatment for the winter, however, this year, my symptoms feel a bit different from previous winters: on top of the usual depression, I also feel anxious and edgy. Will my light box help the anxiety too? From reading your site, I’ve seen that some people get agitated as a side-effect of using their light boxes, and although that hasn’t happened to me in the past, I certainly don’t want to feel more tense than I do now. Thanks for any guidance you can provide.

Although SAD is often characterized as a “lethargic” depression, in fact, anxiety symptoms are present in a majority of cases. Your case is more complicated in that previous winters were without such symptoms, and your case is not simple SAD. Light therapy elicits anxiety symptoms only in a small proportion of patients; in most cases, patients find it energizing yet calming (not really a contradiction in terms!). When anxiety symptoms occur as a side effect, this is almost always a sign of “overdose” that is correctible by reducing intensity or exposure duration or scheduling the lights later in the morning. Clinical guidance and monitoring are a sine qua non. Also, keep in mind that although anxiety symptoms are often secondary to depression, an anxiety disorder can be primary, in which case we do not recommend light therapy.

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What is your opinion about the safety and efficacy of green light boxes? A manufacturer cites some research to support the claim that these are as effective as the more commonly used white light therapy devices, but are much safer for the user’s eyes.

There are certainly no definitive data to support these claims. Professional consensus remains that bright white fluorescent light boxes are the clinical standard. They have been thoroughly tested in multiple, independent clinical trials and their safety (barring UV and excessive blue light emission) has been documented in long-term studies. White light contains elements throughout the color spectrum, including green. The inclusion of a small amount of blue light in white light is thought to enhance circadian rhythm phase shifting, which may be an element of antidepressant action. Green light exposure needs to be greatly intensified in order to match the phase shifting efficacy of small amounts of blue. How the various spectral components contribute to the antidepressant effect is still unknown. Ergo: don’t jump on an isolated spectral component and expect it to perform equally or better (or to be safer) than white light

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I suffer from panic disorder. I used a light box for four days for 30 minutes starting at 6:30 a.m. On the fourth day I experienced a severe panic attack which lasted from about 8:00 P.M. thru 5:00 A.M. I did not continue using the light. The following day I slept through the night. The last two nights I have had the same intense anxiety. I can’t sleep at all at night. Could I have messed up my internal clock and will it ever go back to normal? I need to get up for work at 6:00 a.m., but I can’t even fall asleep until then. I don’t know what I should do. Any advice would be greatly appreciated.

Very sorry to hear this, but you have provided an important lesson for others. Light therapy is not advised for people with panic disorder–indeed, everyone with a “DSM-V Axis I” diagnosis should use lights only under doctor’s supervision. You should contact your doctor immediately for medications that will relieve your current symptoms. Don’t worry about your internal clock, it will readjust quickly on its own. Your being awake all night is most likely a side effect of light-induced anxiety and hyper-activation that will subside. If you were trying to treat depression with the light, that might still be possible with a far lower dose of light, but now you have seen the risk involved.

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I have recurrent ocular herpes for which I take Valtrex every day. Are there any concerns that light box therapy can exacerbate it?

Valtrex is not a photosensitizer, so there is not obvious contraindication for its use with light therapy.

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I have been using a light box, the one you recommend, for about a month. I use it for a half hour, generally between 7:30-8:00 AM during the week and at 8:30-9:00 AM on weekends. I was not depressed when I started using it. My therapist and pharmacologist suggest that I use it as a buffer from depression. How long do you suggest I use the light box? Can I stop during the spring and continue again in the fall or winter? I have a bipolar illness, and have been stabilized for 10-15 years. However, I am very light sensitive. I feel uncomfortable in dark places, and much better in the light. I am somewhat a fanatic about that.

No one has ever demonstrated that light therapy buffers against depression in non-depressed people, although that is conceivable. Not to throw cold water on your doctors’ strategy, but it is also possible they think using a light box would help maintain your good mood through its placebo effect. However, if difficulty awakening has been one of your problems even when you’re feeling well, the light box could be useful. And the light box can be used in conjunction with meds to enhance overall response–that is, to reduce the residual symptoms that meds fail to treat. If your historic problem is winter-seasonal, it makes sense to discontinue lights in early May, but if your historic problem is non-seasonal, whatever benefits you are finding with light could last year-round. Obvious strategy: if you begin to slump when you discontinue the lights, resume them!

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What is the evidence to support the use of light therapy to treat behavioral problems in the demented elderly? (I would like to read the research studies.) How does is it thought to work?

Quoting from Dr. Terman’s 2005 CNS Spectrums review (downloadable at “Light therapy for elderly patients deserves separate mention. Although its use to alleviate disruptive and cognitive symptoms of senile dementia has been extensively investigated, a review of the effect on sleep and behavior found the results inconclusive, with further confirmation in another Cochrane review that also considered effects on mood. Few light therapy studies have focused on geriatric depression, per se. A small crossover study (N=10) in institutionalized patients without MDD but with moderate-to-high Geriatric Depression Scale scores tested morning bright versus dim light (10,000 lux versus 300 lux, 30 minutes, 5 days), and obtained significant mood improvement under the active condition. In Taiwan, a trial of hospitalized patients with MDD (N=30) found alleviation of depressive symptoms after 5 days of morning light treatment (5000 lux, 50 minutes) in comparison with an untreated control group. However, the largest such trial (N=80, 5 weeks) found no significant benefit of bright light (10,000 lux, 1 hour; morning, midday, or evening) over a 10-lux dim red control. This raises doubt about the general utility of bright light therapy for geriatric depression, even though there was a trend toward greater improvement with morning exposure.” See the references in the paper, and you will have a route into the literature.

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I have just been diagnosed with delayed sleep phase. My body clock tries to make me sleep from 2 a.m. until 10 a.m., but I must wake up for work at 5:30 a.m. The doctor prescribed Ambien, but after trying it, I still have great difficulty waking up, even after eight hours of sleep, and am very groggy all morning. My doctor and I discussed light therapy but he didn’t seem to feel I needed it since my delay was not severe. I wonder if the medicine is making me fall asleep on time, but my body is still producing melatonin at the wrong time. Could this be the problem and could light therapy help? I am a teacher and in the summer when I’m not working, I sleep until 9 or 10 a.m. and then spend time outside. I don’t have a sleep problem then.

Very well expressed, but you are presenting a complex of issues. Mostly importantly, your doctor is wrong: light therapy provides a very effective solution to mild sleep phase delay. Beyond that, your delay is about three hours, which we would consider quite serious. A major complication involves your workday rise time at 5:30 a.m., however. If you were to take light treatment at such an early hour, it would act to exacerbate your delayed sleep phase. To move your body clock earlier, the light therapy strategy requires using lights near the end of your “internal night,” most likely after 8 a.m. when you are already out of the house. You could get a grip on this problem in late summer or on winter vacation. After a few days of light at 8 a.m., you would begin to step up the light progressively earlier in order to advance your body clock. You might also make headway by using low dose slow-release melatonin at about 10 p.m., whether or not in conjunction with light, and then moving the dose progressively earlier. Because of the complexity of your situation, we urge proceeding under expert clinical guidance. For relevant background, see the Termans’ chapter in Principles and Practice of Sleep Medicine, downloadable free at And perhaps share it with your doctor!

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I believe I have SAD as I know my body and mind respond favorably during summer months and I get depressed when we lose daylight hours. I have also always been prone to depression, worse in winter months. Obviously SAD is proof positive of a circadian rhythm disturbance. Because I’ve always been a “night owl,”, I’ve investigated sleep disorders and found out about delayed sleep phase disorder (DSPD). My “body clock” can literally make me turn night and day around if left to my own devices. I was told by my mother that even as a baby she had a hard time getting me to sleep and I’ve always been unnaturally tired in the morning even with a full 8 hours sleep. My question is, would light therapy be useful in my case?

Glad you’re gaining this insight. Delayed sleep phase, difficulty awakening, and depressed mood often come in a “package”, whether seasonally or non-seasonally. Light therapy has been designed and tested for this indication, and we urge you to try it. We can’t be sure from your description, but it sounds like successful treatment may require clinical supervision with dosing adjustment of the light (intensity, exposure duration and time of administration), possibly in combination with other chronotherapy procedures. Thanks for writing.

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I purchased a negative air ion generator from the CET store almost two years ago and it has improved my life immeasurably. I am less depressive and it seems to have also had the happy “side effects” of significantly reducing my snoring as well as some sinus problems. Obviously anecdotal accounts such as mine are easily discounted, but the clinical research (including that supported by CET) should be harder to ignore. Yet, it seems that almost no clinicians are presenting air ionization to patients as an option and interest in air ionization continues to be mostly confined to a relatively small community of researchers. Do you have any thoughts as to why negative air ionization does not appear to be making much progress in the medical community at large?

Amen and amen. Moving the medical establishment is one obstacle–we are learning that the new generation of psychiatric residents is far more receptive to these ideas than their elders steeped in psychopharmacology, but that portends a generational shift that could take 20 years. Additionally, the FDA provides us no attention, we think because manufacturers are happiest to make a ‘quick buck’ without regulation, and won’t submit (expensive) applications for prescription approval. From CET’s point of view, the major result is the absence of research support that would lead FDA to satisfaction with this significant, non-phamaceutical medical innovation. It is very important for people like you to make their personal findings known and try to jog the system…

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Have any studies been conducted in a clinical setting on the possibility of adverse effects on the retina with any light source of 10,000 lux?

The largest study, for 10,000 lux, 30 min daily exposures for up to six winters, was reported in the American Journal of Ophthalmology (for a download, go to No ocular abnormalities occurred. The authors concluded that light therapy “appears safe for the eyes. Current knowledge is insufficient to specify any definite ocular contra-indications for bright light therapy, although we recommend that patients with preexisting ocular abnormalities and those using photosensitizing drugs undergo treatment only with periodic ophthalmologic examination.” Although there are no definite coutra-indications, we also recommend that alternatives to light therapy be used by patients with retinal degenerative disease

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Is light therapy safe for the eyes?

The largest study, for 10,000 lux, 30 min daily exposures for up to 6 winters, was reported in the American Journal of Ophthalmology (for a download, go to Dr. Gallin’s paper in the SAD section of Treasury of the Literature, under the EDUCATION tab at the top of the page). No ocular abnormalities occurred. The authors concluded that light therapy “appears safe for the eyes. Current knowledge is insufficient to specify any definite ocular contra-indications for bright light therapy, although we recommend that patients with preexisting ocular abnormalities and those using photosensitizing drugs undergo treatment only with periodic ophthalmologic examination.” Although there are no definite countraindications, we also recommend that alternatives to light therapy be used by patients with retinal degenerative disease.

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Are there any New York State programs that will offer free treatment for a bipolar adult? He is just a little over the line for “Healthy New York,” but doesn’t make enough money to buy insurance, and his meds are very expensive. He will not be able to buy them and this is not good.

Patients can inquire about the sliding-scale Residents’ Clinic at Columbia University Medical Center by calling the referral line, 212-305-6001. If that program is not suitable, the patient will be given additional leads. There are also opportunities at the New York State Psychiatric Institute for participation without cost in bipolar depression research studies that provide excellent care. Again, call the referral line.

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What kind of light therapy would be most appropriate for a person at risk for macular degeneration? I have been seeing advertisements for green light, but my ophthalmologist is not familiar with this type of treatment.

To our knowledge, there have been no safety studies of narrow-band green light therapy, while there has there been extensive investigation of 10,000 lux broad-spectrum light therapy showing no adverse ocular events (you can download some of this literature from our website). Furthermore, thus far there have been no definitive studies showing antidepressant efficacy of narrow-band green light therapy, in contrast to positive studies of 10,000 lux broad-spectrum light.

All that said, patients at risk for macular degeneration are strongly advised to use light therapy that excludes intense exposure to the short-wavelength spectrum (the blue component of white light), including such exposure from outdoor light and full-spectrum light sources. As a general guideline, lamps of 4000 Kelvin color temperature and below (soft white) are considered protective.

Our recommendation would be to try broad-spectrum bright light therapy with blue-blocking wrap-arounds such as Fit-Over w/Side Shields, 65% light yellow (models L58,U58,S58), A second, well-tested alternative is dimmer, incandescent illumination with dawn simulation in the bedroom. You can read about this on our website. We do suggest that you help bring your ophthalmologist up to speed on these matters, perhaps starting with the 2005 review article in the journal CNS Spectrums, also downloadable from our site.

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My husband and I practice natural family planning using the sympto-thermal method (info: Charting my waking temperature at the same time each day is important to identify the thermal shift that occurs after ovulation. I would like to wake up after taking my temperature, but never do. Right now, I don’t see a problem with applying CET’s timing prescription for optimum light therapy (Automated Morningness-Eveningess Questionnaire, AutoMEQ), in which case I would wake up and use the light at 7:45 AM. However, will using this therapy possibly artificially alter my normal waking temperature?

Good and important question. Morning light therapy is designed to shift your circadian rhythms earlier, which is a key factor for (a) the antidepressant effect, and (b) counteracting the pressure to oversleep. Body temperature — especially at night — is strongly influenced by the internal circadian clock. Therefore, you can expect that your morning temperature before getting out of bed will be higher after you begin light therapy. That is not because light therapy raises temperature, but rather because morning light therapy shifts your entire temperature rhythm earlier, by perhaps 1-3 hours. (Your lowest point on the 24-hour temperature cycle–the temperature “nadir”, which occurs about 2 hours before waking–will also shift 1-3 hours earlier.) Therefore, you can expect that your wake-up temperature will be higher all across the month. However, your daily record will quickly re-stabilize, and its shape across the month will be similar to what you see now.

All that said, the important news of 2006 (see our News & Comment section) is that morning light therapy also regularizes the time of ovulation. Ovulation thus becomes more predictable, and in women with cycles longer than 28 days, the cycle can normalize. Indeed, morning light therapy has a stimulating effect on sex hormones, and can serve therapeutically to increase the chance of ovulation at mid-cycle at the same time it normalizes cycle length. As such, morning light therapy can serve two important goals: guarding against pregnancy in women who want to avoid it, and enhancing the chances for women aiming to become pregnant.

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I have several questions about medication for treating SAD. I have heard of agomelatine, a new (but not yet available) antidepressant that has effects on melatonergic receptors. Do you know of any benefit by this medication for treating SAD? Is there any evidence of a possible effect of taking serotonergic drugs for treating SAD? Is the pharma industry doing any research to create a drug specially designed for SAD?

Agomelatine is a promising new antidepressant being developed by Servier in Europe and Novartis in the USA. It is an oral melatonin receptor stimulator and a serotonin receptor blocker. Many experts think that its antidepressant effect is achieved primarily through its effects on serotonin receptors, but some think that the melatonin effect also contributes to the antidepressant effect. It has been shown to be effective in shifting circadian rhythms in humans and that might make it helpful for treatment of SAD, but this remains to be tested.

The evidence supporting the usefulness of serotonergic drugs (SSRIs) for SAD is very limited. Glaxo’s Wellbutrin XL (which has combined dopaminergic, serotonergic, and norepinephrine-receptor-blocking action), and is currently on the market, was approved by FDA in 2006 for the prevention of SAD. It was already on the market for the treatment of major depression (including SAD). All things considered, a drug that works for one kind of depression is likely to work for other types as well.

On the other side of the coin, the environmental therapies — light and negative air ionization — originally developed for treatment of SAD have now been shown also to work for non-seasonal depression. Indeed, recent clinical work shows that some patients (seasonal or non-seasonal) who have failed to respond to drugs — “medication-resistant” cases — respond well to light therapy. Finally, in cases of partial response to drugs or light therapy, their combination can be effective.

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How many hours a night of sleep does an adult need to stay healthy? Does alcohol help you get a good night’s rest?

Sleep need varies widely among individuals. A sign that you’re not getting enough is when you find yourself sleeping longer hours on days off compared with work days. Your goal should be to sleep the same hours all week long on a schedule that allows you to feel alert and energetic during the day. Statistically, it has been suggested that people who chronically sleep very long OR very short hours (for example, 10 hours or 5 hours) may have shorter life expectancy: but that’s just statistics, and doesn’t apply in every case. Some people sleep longer when they become depressed (or they become depressed when they sleep longer — we’re not sure!). In such cases, morning light therapy with earlier awakening can do the trick. Such people are often amazed that they do better with less sleep, and their impression that “if I could only sleep longer, I’d have more energy for day ahead” is proved wrong. As for alcohol, it may help knock you out, but the resulting sleep has poor physiological restorative quality and often leads to multiple awakenings during the night. Don’t do it!

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How on earth can we find a local professional who can advise us on light therapy for my daughter? We have met with her doctor and the local mental health people, and she sees a counselor in a city near us. They all think light therapy may be useful, but can’t figure out who to refer us to! Is there a number to call to find out what (reliable) practitioners are available in our area who know how to prescribe light therapy? Or where the closest such professional is?

Unfortunately, there are still very few light therapy specialists among psychiatrists and psychologists in the field. There are three possibilities, however: (1) Email the Society for Light Treatment and Biological Rhythms and ask if they have a clinician referral in your area. (There are about 100 such across the country.) (2) Check the research center listing on our website If there is a center in your area, it is possible that they will know of clinicians who offer open treatment. (3) Contact the national Center for Light Treatment and Biological Rhythms, a service of New York-Presbyterian Hospital. Outpatients from all over the country are supervised by the Center, although they must come once to New York for initial evaluation.

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I’d like to try a dawn simulator because I want to get up at 6 a.m., and the sun isn’t up yet (and the alarm is horribly jarring). But I’ve also had symptoms of SAD for a long time, and am considering a light box. Is there any reason not to do both? Is there any way to effectively combine them–i.e., use a dawn simulator hooked up to a light box?

Good question. A paper that came out in the December 2006 American Journal of Psychiatry reports that naturalistic dawn simulation (as described on our website) produces a similar effect to post-awakening bright light therapy for treatment of SAD. The implication is that you probably don’t need to combine the two methods–either one can work on its own. We sometimes combine the two for additional effect when patients (a) are sleeping very late, into the afternoon, and need to adjust their internal clocks earlier by several hours, or (b) awaken successfully with the artificial dawn but feel they need an additional energy burst to jump start the day. You cannot connect a dawn simulation controller direct to a bright light box, because the fluorescent lighting system is incompatible with the dimming circuitry. Thus, if you are using both methods, you will need a separate incandescent bedside lamp with adequate projection toward your bed (as described on our website).

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I have been self treating with a light box successfully for several years. My AutoMEQ test directed me to a 545am wake-up time, and my body wakes at that time daily. However, I wake up several times a night and also routinely around 4am, and can’t go back to sleep. I go to bed between 930 and 1030pm. It never occurred to me that the early awakening may be due to my use of the light box. Any suggestions are welcomed. I would also like to know your thoughts on using the light box year round. Thank you.

You’re right: it is quite possible that you are using the light box too early, for too long a duration, at too high an intensity—or combinations of these dosing factors. Let’s assume you are taking a 30-minute treatment session at 545am, while having woken up prematurely at 4am. As a first step, see whether delaying light therapy to 615am resolves the problem, fully or partially. You may have to play with session timing to get it right. You may also need to reduce session duration from 30 to 20 minutes, for example. The AutoMEQ gives a starting point for finding the precise session time to serve your need best—and that time may vary at different times of year. If the sun is rising at 5am in the summer, for example, you may need to reduce the light dose because natural dawn illumination is doing the trick for you. In the fall, if you start waking up later, you would resume treatment. This guideline applies whether or not you experience SAD.

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If I get a light box, will I have to take my eyeglasses off? They have filters to make them darker in the sun.

Try an experiment first. Place your eyeglasses right up to a regular fluorescent bulb (obviously, not while wearing them!) If they remain clear, there will be no problem. If they darken, you should substitute non-filtering lenses, if needed, to read while taking light therapy.

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I notice an antidepressant effect if I use my light box in the early morning. However, I am phase-advanced, so I do not sleep well if I use the light in the morning. However, when I use the light in the evening, I do not notice an antidepressant effect. Would I get the effect by using the light in the mid-morning plus the evening?

There is no harm trying, but we cannot confidently predict the result. It has been hypothesized that “early types” need a phase delay (from evening light) to show the antidepressant effect, while “late types” will respond to phase advances (from morning light). Thus far, there are no strong data to support for that hypothesis — most people respond to phase advances, regardless of their chronotype.

You might find the following trick helpful: use the light in late evening, right before bedtime, for one week. (You may find your sleep episode delays.) Then, immediately switch to morning light at your new wake-up time. That will give you the desired phase advance, and your sleep may stabilize without premature awakening.

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Is it safe to use a sunbed while I am pregnant?

It is never safe to use a sunbed, because of carcinogenic ultraviolet radiation. Pregnancy per se is not the issue.

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I have always been a “night person.” I have children now and I bear the responsibility of getting them off to school in the morning. I work nights as a nurse 7 p.m. – 7 a.m., 3-4 nights a week. My question is, can light therapy work for my mild depression? I am pregnant and have NO interest in exposing my child to antidepressants. Is it possible that I am just doomed to live with this, since I have a schedule that prevents me from going to bed and waking up at about the same time every day?

This is a vexing situation, which unfortunately is not that unusual. Light therapy may still help, but the combination of your intermittent night shift and need to sleep during the day, plus your pregnancy, offers no simple solution. With monitoring by your doctor, we would recommend first trying a steady midmorning treatment schedule. Following the 3 nights you work, wait till after completing the treatment before going to sleep. Another possibility is trying light treatment on awakening, but only on the 4 mornings you have slept a normal night. If at all possible, we suggest petitioning your hospital for a day shift throughout your pregnancy and for the first few months after the baby arrives.

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Can light therapy alter endocrine hormone levels? There may be some evidence that TSH levels can be affected, but what about prolactin?

The strongest evidence for light therapy effects on hormones is for melatonin. When the lights are on and bright, nighttime melatonin production rapidly and reversibly turns off. There is certainly more to learn about this complex subject. In one study of SAD patients, light therapy did slightly lower plasma prolactin levels. However, there was no significant effect on other hormones studied. Another study showed no effect of light therapy on prolactin, but did find reduced TSH levels at night.

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Why am I so tired in the morning during the winter months?

Our internal biological clock–which strongly influences our daily patterns of alertness and energy, sleep and waking–is very sensitive to early morning illumination. Since the sun rises later in winter (in the northern hemisphere above the equator), the biological clock is vulnerable to drifting later, leaving us tired in the morning. The essence of morning light therapy is to correct that drift, thereby restoring normal morning energy and alertness.

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I seem to have reverse SAD–every year I get depressed in April and it gets worse until end of summer. I feel my best from September to March. Would negative air ion therapy be of any help to me? I almost feel like shutting myself in a dark, cool room to get relief.

A small minority of people with seasonality experience summers worst and winters best. There have been no clinical trials on the effectiveness of negative air ion therapy in this group. Possibly it might work–and if so, it could be preferable to the use of antidepressant drugs. One encouraging lead comes from a recent study of patients with chronic depression, who are depressed all year long, without seasonality. Interestingly, many of them did respond to negative air ion therapy, even during the summer. So, we think it’s worth a try under clinical supervision.

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Does the changing length of day and the time of natural sunrise/sunset affect the optimum-time calculation for light therapy?

Only indirectly. Our internal circadian clock adjusts seasonally to the dynamically changing time of sunrise. Therefore, if you complete the Automated Morningness-Eveningness Questionnaire in the spring, you are likely to have a different score than if you take it in the winter. In general, people with SAD score lower — or show greater eveningness–in the winter than in the spring.

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Can children under the age of two suffer from SAD? I have a 20-month-old grandson, and since he has been about three months old, I have been keeping track of his daily moods. When it is cold outside and the shades are drawn–or just a basic cloudy day–there is no living with him. On sunny days, he is totally the opposite. I have expressed my concerns to my daughter. She asked our pediatrician, who says, “He is just a baby.” Should we start keeping a journal?

Strictly speaking, one cannot diagnose SAD in a 2-year-old, because winter depression has to have occurred throughout each of the last two years (with summers consistently good), and one cannot reliably assess conventional childhood symptoms of depression at such a young age. Still, your grandson might be weather- or light-sensitive in a way that causes severe behavioral disturbance. The pattern might even be a precursor to SAD. SAD has been treated with light therapy in kids as young as 6 years. Yes, you (or your daughter) should certainly keep a journal, to be able objectively to summarize the pattern as it may continue. Additionally, you might think about placing a dawn simulation system in the baby’s bedroom, with “sunrise” set to the desired morning wake-up time. This is an innocuous, healthful intervention that might override the negative effects of light deprivation. See the apparatus description at the CET Store.

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How can I determine the optimal number of hours of sleep for me? I have noticed that when I wake up 30 minutes earlier than my usual time, I feel more refreshed than on other days. However, I am not sure whether that is due to the amount of sleep I am getting–less than usual–or the time I am waking up.

Every person has an individual sleep need, but we have no direct way to measure it. Many people sleep longer than necessary or desirable, often on the erroneous assumption that more sleep leads to greater daytime energy and alertness. For people vulnerable to depression, excess sleep can be depressogenic–that is, it can trigger blue mood and increased daytime fatigue. In such cases, shorter sleep is actually advantageous. If you find that waking 30 minutes earlier than usual makes you feel better, that is a strong clue that you are sleeping too much. You can test this by waking earlier for a whole week, to ascertain whether the accumulated sleep reduction begins to make you sleepier, rather than more energetic.

Many people get inadequate sleep during the week, because of the pressure of work schedules. They find themselves needing “recovery sleep” on the weekends. For those people, additional reduction of weekday sleep time is not recommended. To further answer your question, the critical factor is probably the amount of sleep you are getting, not the time you are waking up. On the other hand, waking up to bright morning light, whether from outdoors or timed artificial light sources, is far more healthy than waking in a dark bedroom.

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