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Coping with Darker Times -- Treating Seasonal Affective Disorder
November 26, 2008  By Michael Craig Miller, M.D.
Harvard Medical School Here in Boston, we've had another unseasonably warm autumn. Some of us worry about climate change and others simply enjoy the extra coat-free days. But, no matter what the temperature, it's still dark at 5:00 p.m. And that, to many of us, feels lousy. For some of us, the lousy feeling is a sign of seasonal affective disorder or SAD. Significant mood changes occur that can't be dismissed with a shrug. The most common form of this disorder tends to start in the fall and gets worse in January and February. Relief comes with longer days in the spring. About half a million Americans meet diagnostic criteria for SAD. Many more people have milder mood symptoms. Symptoms may include loss of pleasure and energy, feelings of worthlessness, inability to concentrate, and an uncontrollable urge to eat sugar and high-carbohydrate foods. Back to top Standard Light Therapy Bright white light therapy has been used to treat seasonal affective disorder since the mid-1980s. It involves sitting close to a fluorescent light box for 30 minutes, usually in the morning on waking. The light is much more intense than an ordinary light bulb. Proper light boxes provide 10,000 lux. (The "lux" is a measure of light intensity. By way of comparison, indoor light is about 100 lux, while a bright sunny day is 50,000 lux or more.) Bright white light acts on cells in the retina that connect to the hypothalamus, a part of the brain that helps control circadian rhythms. These rhythms are thought to be disrupted in seasonal affective disorder. Two reviews of studies on light therapy found that it was as effective at treating seasonal affective disorder as antidepressant therapy. In some cases it was more effective. Although it is a mainstay of treatment, researchers have been looking for ways to improve and refine it because: - It doesn't work for everyone. Studies have reported that 50% to 80% of patients get complete relief from depressive symptoms after bright light therapy. But that still leaves many patients who don't find it helpful.
- Successful treatment may depend on carefully individualized timing and dosing of light. The light dose depends on the strength of the light source, the patient's distance from the light, light wavelength and duration of exposure. The recommendation for 30 minutes of daily exposure to 10,000 lux is based on average response to white light; some patients may not need that much exposure to benefit. Other people, such as parents of toddlers, may not be able to sit in front of a device for 30 minutes each morning.
- Some people don't tolerate bright light. The biggest psychological risk is that bright light therapy may trigger hypomania or mania in patients with bipolar disorder. Mood-stabilizing medications can be given to reduce that risk.
- Bright light can cause retina damage, although it's rare. Some medications can increase the risk, including some antipsychotic medication, lithium, melatonin and St. John's wort. A few medical conditions can also increase risk: People with diabetes or pre-existing retina disease should discuss their conditions with their doctor before trying bright light therapy.
Back to top Enhancing Light Therapy Researchers are looking at ways to improve the response or reduce the risk of side effects like mania or retinal damage. Here's how: Better timing Abnormal sleep rhythms are common in depression. The hormone melatonin, which helps regulate the cycle of waking and sleeping, may play a role in SAD. The brain makes melatonin and usually produces more of it during the early evening. The timing of this surge varies from person to person. Researchers from Columbia University reported that remission from SAD was twice as likely if light therapy was precisely calibrated to these fluctuations in melatonin levels. They found that 80% of patients achieved remission if light therapy began 7½ to 9½ hours after an evening melatonin surge, compared with 38% of patients whose light therapy began 9½ to 11 hours after the surge. Individual melatonin shifts may vary by as much as six hours, which partially explains the difference between early birds and night owls. Melatonin is hard to measure, but the nonprofit Center for Environmental Therapeutics offers a free online Morningness-Eveningness Questionnaire (MEQ) that may help gauge the timing of therapy. Dawn simulation In this variation of light therapy, a preset light device turns on before a patient wakes up. Light intensity increases gradually from 0.001 lux (equivalent to starlight) to 250 or 300 lux (similar to sunrise) over a period of 90 minutes. Some small studies have found promising results with this technique. Blue light Traditional devices use white light, a mixture of all the colors (such as blue, green and red) in the visible light spectrum. The use of light-emitting diode (LED) technology has made it possible to create smaller and more portable devices, and to test specific wavelengths of light. Studies have found that ganglion cells in the retina are particularly sensitive to blue light. This suggests that this wavelength may powerfully affect circadian rhythms. Researchers are investigating whether blue light might provide the same benefit as white light but with less exposure time. It may also reduce the risk of side effects or discomfort. Blue light may have its own special risks, since some wavelengths of blue light may cause retinal damage. Back to top What You Can Do Today Experts recommend that patients with seasonal affective disorder first try traditional bright white light therapy after awakening. If it does not help or it creates bothersome side effects, it may be worth trying antidepressants or one of the alternatives under investigation. Although light treatment is relatively safe, there are a few cautions if you want to try it. - Discuss your mood problem with your doctor, who may advise you to see a mental health professional before trying light therapy.
- The U.S. Food and Drug Administration does not test, approve, or regulate light box devices.
- Before buying any light box, consider asking about wavelengths (to avoid wavelengths that might be harmful) and check to see if it has been used in any reputable research facilities.
- Before investing your money and time pursuing bright light therapy, work with a professional who is qualified to make a diagnosis, in order to evaluate your individual situation, and to determine whether a diagnosis of seasonal affective disorder is correct.
- Depression has many causes and there are many good ways to treat it. Review all your treatment options. Establish a relationship with a professional who can help you periodically review your progress.
Back to top Michael Craig Miller, M.D. is editor-in-chief of the Harvard Mental Health Letter and an assistant professor of psychiatry at Harvard Medical School. Dr. Miller has an active clinical practice and has been on staff at Beth Israel Deaconess Medical Center for more than 25 years.
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