Seasonal Affective Disorder

Behavioral Health Update
BHSI Newsletter Vol. 4, no. 1

Seasonal Affective Disorder
Susan Arquette, Ph.D., L.P.

Seasonal affective disorder (SAD) was officially recognized as a distinct disorder about 20 years ago. More common in higher latitudes and thought to be more influenced by day length than temperature, it consists of a pattern including some or all of the following: depressed mood, decreased energy, increased need for sleep, loss of interest, enjoyment and motivation, increased appetite and/or cravings for sweets or carbohydrates, with associated weight gain. Onset is typically late fall to early winter, with symptoms remitting in Spring. A recent NIMH-funded study1 concluded that most SAD symptoms can be traced to a disruption of body rhythms resulting from winter’s late dawn and early dusk.

Treatment of SAD using full-spectrum lights was proposed many years ago, and research has established light therapy as safe and effective. In many studies light therapy provided benefits equal to those found with antidepressant medication, often with faster results. While light therapy is the treatment of choice for SAD, other therapies also have been shown to be effective, either alone or in combination with light therapy. Lewy and colleagues1 found that administration of small amounts of melatonin, usually in mid-afternoon, was a useful adjunct to morning light therapy in restoring normal daily rhythms and alleviating symptoms of SAD. Light therapy can be effective for a range of depressive disorders beyond its traditional use to treat seasonal affective disorders. It offers a safe alternative to antidepressant medication during pregnancy, and shows some promise in the treatment of premenstrual dysphoric disorder. It also has been used successfully for treating jet lag and sleep disorders among shift workers.

The standard dose is exposure to 10,000 lux of diffused white fluorescent light upon awakening in the morning. The timing and duration of light exposure can be tailored to individual needs, with some people benefiting from a longer exposure and others doing well with less. There has been much research and debate about the type and intensity of light that is safest and most effective. It is inadvisable to construct home-made light boxes due to the possibility of eye injury. The light apparatus should filter out wavelengths less than 450 nm to avoid damage to the eyes. Certain photosensitizing medications, including many standard antidepressants and
antipsychotics, can interact with ultraviolet and short-wavelength blue light with the risk of retinal damage. People who are taking medication should check with their physicians before beginning light therapy to avoid the possibility of eye damage. More information about commercially available lights and features to look for is available at the website of the Center for Environmental Therapeutics,

An intriguing adjunct to light exposure is “wake therapy” consisting of either a full night’s sleep deprivation or sleep deprivation for the second half of the night only. This therapy is surprisingly effective for many types of depression, but the benefits wear off quickly when normal sleep is resumed. Some researchers have combined wake therapy with instructions to the patient to go to bed at 5:00 pm the following evening, with bedtimes advancing by two hours each night until a normal sleep-wake cycle is established. Light therapy and sleep phase advance have both prevented relapse after wake therapy. “Dawn simulation”--- exposure to light that gradually increases in intensity to mimic a natural dawn--- is also effective.

Cognitive behavioral therapy with a specific focus on seasonal issues and behavioral changes including engaging in enjoyable outdoor winter activities have also been demonstrated to be effective treatments for SAD, and the latter combines the known antidepressant benefits of exercise with those of light exposure.


1Lewy, Alfred J, Lefler, Bryan J, Emens, Jonathan S and Bauer, Vance K. (2006).
The circadian basis of winter depression. Proceedings of the National Academy of Science, Vol. 103, No. 19, 7414-7419.

Susan S. Arquette, Ph.D., L.P. is a psychologist at BHSI in Woodbury. She is the Director of BHSI’s Woodbury and Fridley clinics, and is BHSI’s Director of Regulatory Compliance.