What is seasonal affective disorder (SAD)? Everyone gets 'the winter blues' — what's different about SAD?

Many people complain of feeling down, having less energy, putting on a few pounds, and having difficulty getting up in the morning throughout the dark, short days of winter. People suffering from SAD experience these and other symptoms to such a degree that they feel unable to function normally. They often feel chronically depressed and fatigued, and want to withdraw from the world and to avoid social contacts. They may increase their sleep by as much as two hours or more per day, have greatly increased appetite — sometimes accompanied by irresistible cravings for sweet and starchy foods — and gain a substantial amount of weight. Women frequently report worsening of premenstrual symptoms. People with SAD suffer in the extreme the kinds of changes that many others experience to a much lesser degree in wintertime.

An individual SAD sufferer, however, need not show all the symptoms described above. Sleep duration, for example, may be normal, while carbohydrate craving may be extreme, or vice versa. Sometimes a symptom in the cluster is actually opposite the norm, such as insomnia as opposed to excessive sleep. A firm diagnosis of SAD requires evaluation by a psychiatrist, psychologist, or social worker. We caution against attempting self-diagnosis; it is easy to misinterpret symptoms or incorrectly rate their severity. But we offer a provisional diagnostic self-test with personalized feedback you can show to your doctor.

Recent studies indicate that about five times as many people may suffer from "winter doldrums," a sub-clinical level of SAD, than from a level of clinical severity. These people notice the return of SAD-like symptoms each winter and are bothered by them, but remain fully functional. About 25 percent of the population at the middle-to-northern latitudes of the United States experience "winter doldrums."

What is light therapy for winter symptoms, and how is it delivered?

Light therapy involves exposure to intense levels of light under controlled conditions. The recommended light therapy system consists of a set of fluorescent bulbs installed in a box with a diffusing screen and set up on a table or desktop at which one can sit comfortably for the treatment session. Treatment consists simply of sitting close to the light box, with lights on and eyes open. Looking at the lights is not recommended; rather, people are free to engage in such activities as reading and writing, or eating meals. What is important is to orient the head and body toward the lights, concentrating on activities on the surfaces illuminated by the lights, and not on the lights themselves.

Treatment sessions can last from 15 minutes to two hours, depending on individual needs and equipment used. In clinical trials at Columbia University Medical Center in New York, with over 300 SAD patients who used a 10,000 lux system with UV-filtered light diffusion and angular tilt for 30 minutes each day, about 75% showed major improvement of depressive symptoms. Another study found that 30 minutes was an unnecessarily long exposure for some patients (who responded fully at 15 minutes), while several required 1-hour exposures to show the effect. CET offers recommended light therapy apparatus at its online store.

Early research studies used "full-spectrum" bulbs, producing bright light similar in color composition to outdoor daylight, with enhanced short-wavelength (blue) and ultraviolet (UV) irradiation. This proved unnecessary for the therapeutic effect, and actually a drawback in terms of aversive visual glare and skin reactions in photosensitive users. What appears to be critical is that the level of white light produced match that of light outdoors shortly after, which can be achieved with soft white illumination that screens out UV and the extreme blue component of harsh white light. Light intensity is a critical "dosing" dimension of the therapy: systems deliver varying amounts of light, and people vary in their response to light levels. The time of day of light therapy is another important factor. Many people with winter depression respond best of all to treatment first thing upon awakening. It is necessary to determine the optimum time of day for each individual, and CET offers an online questionnaire to help you make the determination.

Is light therapy useful for treating nonseasonal depression?

Recent studies show that light therapy can be helpful year-round for people who experience chronic depression, unpredictable recurrent depression, or bipolar depression, and the method has been effectively tested in patients using medication and even electroconvulsive therapy. The addition of light therapy to the regimen must be under doctor’s supervision.

I'm not depressed, but I have problems falling asleep and waking up on time. Can light therapy help?

Delayed sleep phase disorder, with unusually late bedtimes and rise times, can occur with or without depression. Sleeping pills usually don’t help. Light therapy can be used to normalize the late circadian rhythm when it is used at the end of a person’s “subjective night,” which may be in mid-morning or even mid-afternoon. As soon as wake-up occurs consistently, the timing of the light therapy session is moved earlier in small steps (usually not more than 30 minutes), and sleep restabilized. Eventually, a normal bedtime and rise time is achievable. This procedure is not easy to conduct on your own, and ordinarily requires clinical supervision.

Is increased exposure to normal roomlight therapeutic without the use of a special apparatus?

Some very light-responsive people, living and working in dim environments, may feel improvement with increased exposure to normal room light. Research studies show, however, that most sufferers of SAD and winter doldrums require exposure to light levels much higher than ordinary indoor lamps and ceiling fixtures provide. Such therapeutic levels are five to twenty times higher (as measured in lux by a light meter) than typical indoor illumination in the home or office.

If outdoor light intensities are critical, can the thearapeutic effect be achieved by spending more time outdoors in winter?

Again, some individuals report improvement by spending more time in the sun. For most, however, the strongest therapeutic effect requires exposure to artificial bright light in early morning — at an hour (6:30 a.m., for example) when it is still quite dark outdoors during long winter nights.

Do the lights really work?

Researchers at more than 15 medical centers and clinics in both the U.S. and abroad have had much success with light therapy in patients with clear histories of SAD for at least several years. Marked improvement is usually observed within a week, and symptoms usually return in about the same amount of time when the lights are withdrawn. Most users, therefore, maintain a consistent daily schedule beginning, as needed, in fall or winter and usually continuing until the end of April, by which time outdoor light is sufficient to maintain good mood and high energy. Some people can skip treatments for one to three days, occasionally longer, without ill effect, but most start to slump quickly when treatment is interrupted.

How do the lights work?

The therapeutic level of illumination has several known physiological effects. Blood levels of the light-sensitive hormone melatonin, which may be abnormally high at the start of the day, are rapidly reduced by light exposure. Depending on when bright light is presented, the body's internal clock — which controls daily rhythms of body temperature, hormone secretion, and sleep patterns — shifts ahead or is delayed when stimulated by light. These physiological time shifts may be the basis of the therapeutic response. Light may also amplify the day-night difference in these rhythms. Therapeutic light exposure is also directly energizing, and it stimulates the brain’s serotonin system. It is still not clear whether these actions are independent of light’s effect on the circadian timing system.

Are there any side effects?

Side effects have been minimal. While a small minority of patients experience headaches, eyestrain/irritation, fidgetiness or mild nausea at the beginning of treatment, these usually subside after a few days. If they are persistent, the dose of light can be tapered, most often taking care of the problem. The most dramatic side effect, which occurs quite infrequently, is a switch to an overactive state, during which one may have difficulty sleeping, become restless or irritable, and feel speedy or “too high.” People who have experienced such states in late spring or summer –indicative of hypomania or mania in bipolar disorder – are particularly vulnerable, and guidance by a skilled clinician in the use of light therapy is especially important. Use of a mood stabilizing drug may be needed. If eye irritation persists, it can be alleviated by sitting farther from the lights, using them for shorter periods, installing a humidifier or using artificial tears.

What if I'm pregnant?

Light therapy has been used successfully in several clinical trials with women suffering antepartum depression, whether or not it is in winter. The method offers a safe alternative to medication use, where the fetus might be vulnerable.

Do the lights stimulate vitamin D production? Is that the key to the antidepressant effect?

They should not do so using an ultraviolet-screened light box, as recommended. Small amounts of outdoor light (with UV) stimulate adequate skin production of Vitamin D, although less so in winter in the north. If Vitamin D is an issue, supplement capsules are a solution. Unlike Vitamin D production, light therapy works through the eyes, not the skin.

When are the lights contraindicated?

There are no specific contraindications except in the case of degenerative retinal diseases. As a precaution, patients with ocular pathology should proceed only with concurrence of their ophthalmologist and a schedule of periodic eye exams. Most drug phototoxicity stems from exposure to ultraviolet (UV) light, which is not a problem when using a UV-screened light box. Several drugs (for example, antiarrhythmic medications used to control irregular heartbeat), have been shown to photosensitize to intense visible light, mainly short-wavelength blue irradiation. Caution is warranted in such cases.

Are the lights medically approved? Is a prescription needed? Does insurance cover their cost?

In the sense that your doctor suggests and supervises the treatment, the method is approved. The U.S. Food and Drug Administration, however, does not regulate light therapy apparatus, and in that sense the lights are not considered in the same class as antidepressant medications. People don't need a prescription for lights, but anyone suffering serious depression should certainly seek a doctor's recommendation before obtaining a unit and use it under the doctor's supervision. CET offers an online questionnaire to help you determine whether medical supervision is necessary.

Insurance reimbursement for light therapy apparatus is increasingly available for seasonal depression and circadian rhythm sleep disorders. If your insurance policy covers mental health services, reimbursement will be available for clinical sessions involved in the diagnosis, evaluation for light treatment, and follow-ups.

How much do the lights cost? Can individuals build them for personal use?

The best light boxes are available in the US$200-$300 range. We strongly recommend against home construction of the apparatus. Output must be specifically calibrated for the proper therapeutic effect. There is a real danger of creating electrical or heat hazard, and homemade light boxes have occasionally caused serious consequences like eyelid burning. Apparatus on the market should have been evaluated for output intensity, visual comfort, maximum transmission with minimal heat build-up — and, importantly, clinical efficacy in documented research trials. These factors should be carefully checked before purchasing any light system. See our Criteria for Light Box Selection.

What other treatments are available for SAD?

Recently, using a special electronic device, negative air ion therapy has been shown to alleviate symptoms associated with SAD. A negative ion is comprised of charged oxygen attached to microdroplets of H2O, called superoxide. These charged particles are created naturally outdoors by the roaring surf, thunderstorms, etc. Concentration tends to be higher in summer and in humid environments, and deficient indoors in heated or air conditioned spaces. Such molecules, in high enough concentrations, are capable of making the air cleaner and fresher. This has been shown to reduce irritabililty, fastigue and depression in people with SAD as well as those with nonseasonal depression.

Dawn simulation is subtle form light therapy that looks very promising. In this treatment, you receive light exposure during the final period of sleep. A a computerized timer gradually turns on a lamp with a diffuser, simulating an actual outdoor springtime dawn in the bedroom. This light, which is much less intense than that delivered by light boxes, has been shown to affect the body's biological clock, suppress melatonin secretion, and have an antidepressant effect. Both negative ion therapy and dawn simulation therapy can be administered while one is asleep. Because of this convenience, these treatment options may be preferable to people who cannot schedule a 30-minute bright light session at breakfast time. Bright light therapy, however, is still the most thoroughly tested treatment option.

Aside from these environmental treatments, some sufferers find that standard antidepressant medications provide relief, although we consider this a second choice to be used only if light therapy fails. Antidepressants can also be combined with light therapy when their use separately provides only partial benefit.

Cognitive behavioral therapy has been used to help SAD patients cope with winter systems and adhere to their light therapy regimens.

Copyright © 2007, Center for Environmental Therapeutics