Seasonal Affective Disorder

seasonal affective disorder (SAD), recurrent fall or winter depression characterized by excessive sleeping, social withdrawal, depression, overeating, and pronounced weight gain. SAD effects an estimated 6% of Americans; for reasons not yet understood, 80% of those affected are women. Most children who are affected have a close relative who also has SAD or another psychiatric condition. The disorder particularly affects people who live in the upper latitudes.

Although the mechanism of the disorder is not perfectly understood, it is known to be a reaction to the biological effects of light on the body (see biorhythm). Daily, or circadian, rhythms help animals keep track of the seasonal changes in the environment, such as the shortening of days in winter, so that they can make the adaptive changes necessary for their survival in each season. Two substances, the hormone melatonin and the neurotransmitter serotonin, are a part of this process and are being studied for a possible role in SAD. Melatonin is secreted by the pineal gland, which is in turn controlled by an area (the suprachiasmatic nuclei) of the hypothalamus; the hypothalamus, among other things, performs a clocklike function in the body. The eye's retinal nerves are connected to this area. Melatonin is secreted chiefly at night, and its secretion is suppressed by light. Secretion of the neurotransmitter serotonin declines in the winter and may undergo abnormal declines in those with SAD; concentrations of serotonin are increased by bright light. Serotonin is especially active in the hypothalamus. Decreased sensitivity of the retina has also been implicated as a cause of SAD.

Treatment with bright light (about five to twenty times brighter than normal lighting) often alleviates symptoms within a period of days. Unwieldy lighting paraphernalia has given way to smaller, portable light boxes and lighted visors. Doses range from 30 minutes to a few hours per day, often undergone in the morning to simulate the dawn.

The Columbia Encyclopedia, 6th ed. Copyright© 2015, The Columbia University Press.

Seasonal Affective Disorder: Selected full-text books and articles

The Environment and Mental Health: A Guide for Clinicians By Ante Lundberg Lawrence Erlbaum Associates, 1998
Librarian’s tip: "Light" begins on p. 15
The Origin of Everyday Moods: Managing Energy, Tension, and Stress By Robert E. Thayer Oxford University Press, 1997
Librarian’s tip: "Weather" begins on p. 50
Sensory Research: Multimodal Perspectives By Ronald T. Verrillo; Jozef J. Zwislocki Lawrence Erlbaum Associates, 1993
Librarian’s tip: Chap. 7 "Photoreceptors, Black Smokers, and Seasonal Affective Disorder: Evidence for Photostasis"
Women's Mental Health in Primary Care By Kathryn J. Zerbe W. B. Saunders, 1999
Librarian’s tip: "Seasonal Affective Disorder" begins on p. 39
Emotional Climates: Ritual, Seasonality and Affective Disorders By Harrison, Simon Journal of the Royal Anthropological Institute, Vol. 10, No. 3, September 2004
Peer-reviewed publications on Questia are publications containing articles which were subject to evaluation for accuracy and substance by professional peers of the article's author(s).
How to Beat the Winter Blahs and Boost Our Energy By Starling, Kelly Ebony, Vol. 53, No. 3, January 1998
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