seasonal affective disorder


Also found in: Dictionary, Thesaurus, Medical, Legal, Acronyms, Wikipedia.
Related to seasonal affective disorder: Light therapy

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 rhythm, biologicalrhythm, biological,
or biorhythm,
cyclic pattern of physiological changes or changes in activity in living organisms, most often synchronized with daily, monthly, or annual cyclical changes in the environment.
..... Click the link for more information.
). 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 glandpineal gland
, small organ (about the size of a pea) situated in the brain. Long considered vestigial in humans, the structure, which is also called the pineal body or the epiphysis, is present in most vertebrates.
..... Click the link for more information.
, which is in turn controlled by an area (the suprachiasmatic nuclei) of the hypothalamushypothalamus
, an important supervisory center in the brain, rich in ganglia, nerve fibers, and synaptic connections. It is composed of several sections called nuclei, each of which controls a specific function.
..... Click the link for more information.
; 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.

seasonal affective disorder

[¦sēz·ēn·əl a¦fek·tiv dis′ȯrd·ər]
(psychology)
A syndrome of annually repeating depressive symptoms (usually overeating, oversleeping, and carbohydrate craving) that are related to changes in the season and are responsive to light therapy. Also known as winter depression.
References in periodicals archive ?
Seasonal Affective Disorder and Beyond: Light Treatment for SAD and Non-SAD conditions.
The autumn and winter months can bring on seasonal affective disorder
With some people, reverse seasonal affective disorder (spring and summer) can bring on symptoms of mania or a less intense form of mania (hypomania).
Proposed mechanisms for seasonal affective disorder
Seasonal Affective disorder is believed to produce symptoms of depression during the dark months.
The site also includes information on appropriate holiday alcohol consumption, helping children cope with holiday stress, and managing seasonal affective disorder (SAD).
Seasonal affective disorder affects half a million people.
A SEASONAL affective disorder is caused by a biochemical imbalance, triggered by the shorter daylight hours.
QI SUFFER from Seasonal Affective Disorder and I every winter I struggle not to get depressed.
And it's no laughing matter, according to mental health experts, who've classified the condition as Seasonal Affective Disorder -- SAD -- an illness that affects millions each year.