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!

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.

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.

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 sltbrinfo@aol.com 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 www.cet.org. 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 lightion@pi.cpmc.columbia.edu, 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.

My husband and I practice natural family planning using the sympto-thermal method (info: www.contracept.info/symptothermal.php). 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.

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), http://noir-medical.com/uv_yellow.htm#Light. 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.

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 www.cet.org/resources). 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

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

I bought CET’s recommended light box in early November and can’t even begin to describe what a wonderful addition to my life it has been. I’ve never, ever felt better. I can honestly say that I’ve never been psychologically healthier or happier, not even in the summer. So can I assume that it is safe to continue my use of the light, 30 minutes a day in the morning, during the summer months?

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.

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