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Seasonal Affective Disorder
Seasonal Affective Disorder (SAD) is a type of winter depression which affects millions of people between September and April and in particular during December, January and February. SAD is believed to be related to a biochemical imbalance in the hypothalamus due to the shortening of daylight hours and the lack of sunlight in winter.
For many people, SAD is a seriously disabling illness, preventing them from functioning normally without continuous medical treatment. For others, it is a milder condition, referred to as sub-syndromal SAD, or winter blues, that causes discomfort. There is also a rare form of SAD, known as summer SAD, in which symptoms occur each summer and go into remission in winter.
Symptoms
SAD symptoms usually disappear in spring, either suddenly within a few weeks of hypomania/hyperactivity, depending on the intensity of sunlight in the spring/early summer. In summer, SAD symptoms may be related to excessive heat rather than light and may include irritability and lethargy rather than oversleeping and overeating. SAD may begin at any age, but the onset usually is ages 18-30.
How common is SAD? Between 4 and 6 percent of the U.S. population suffers from SAD, while 10 to 20 percent may suffer from a milder form of winter blues. Three-quarters of sufferers are women, most of whom are in their 20s, 30s, and 40s. Though SAD is most common during these ages, it can also occur in children and adolescents. Older adults are less likely to experience SAD.
What causes SAD?
The exact cause of this condition is not known. One theory is that with decreased exposure to sunlight, the biological clock that regulates mood, sleep, and hormones is delayed, running more slowly in winter. Exposure to light may reset the biological clock. Another theory is that brain chemicals that transmit information between nerves, called neurotransmitters (e.g., serotonin), may be altered in individuals with SAD. It is believed that exposure to light can correct these imbalances.
The master biological clock
A small cluster of brain cells (neurons) dubbed the suprachiamatic nucleus (SCN), has been identified as the probable site where our internal biological clocks are synchronized. The SCN is in a position to coordinate the rhythms of our inner world with the rhythm of the light-dark cycle in the outer world.
SCN eventually sends information to a small gland at the base of the brain called the pineal gland in which the hormone melatonin is produced. The amount of light seems to determine how much pineal melatonin is actually released from the pineal and secreted into the blood stream. The more light, the more release is suppressed. The less light, the more melatonin the blood carries. Light suppresses melatonin release.
What does that mean for the changing seasons?
During those seasons when the photoperiods are long, in spring and summer, melatonin secretion is at its lowest since it can only be secreted at a significant rate during the relatively fewer hours of darkness. On the other hand, the closer we move toward the winter solstice, the fewer hours of light there are each day and, correspondingly, the longer period of time each day for melatonin to be released into the blood stream.
What does melatonin do?
One result found over and over again is that melatonin indirectly causes body temperature to drop, which could contribute to a loss of pep, loss of energy, with sluggishness and perhaps with eventual depression.
Tips for avoiding the winter blahs, blues, or SAD
A number of treatments exist for SAD including:
If your doctor suggests you try light therapy, you may use a specially made light box, or a light visor that you wear on your head like a cap. Generally, light therapy takes about 30 minutes each day throughout the fall and winter, when you're most likely to be depressed. If light therapy helps, continue using it until sunlight is available. Stopping light therapy too soon can allow the symptoms to come back.. Tanning beds shouldn't be used to treat SAD. The light sources in tanning beds are high in ultraviolet rays, which may harm both your eyes and your skin.
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Government/GSA
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