Seasonal affective disorder
Seasonal affective disorder, or SAD, is an affective, or mood disorder. Most SAD sufferers experience normal mental health throughout most of the year, but experience depressive symptoms in the winter. SAD is rare, if existent at all, in the tropics, but is measurably present at latitudes of 30°N (or S) and higher.
Cause and treatment
Connections between human mood, as well as energy levels, and the seasons are well-documented, even in normal humans. Particularly in high latitudes (50°N or S) it is common for people to experience lower energy levels during the winter. Colds and flu also peak during this time, and most people get less outdoor exercise than in the summer.
Seasonal mood variations are believed to be related mostly to daylight, not temperature. For this reason, SAD is prevalent even in mid-latitude places with mild winters, such as Seattle. Prolonged periods of overcast weather can also exacerbate SAD. Normal "winter blues" can usually be dampened or extinguished by exercise and increased outdoor activity, particularly on sunny days, resulting in increased solar exposure. SAD, however, is a more serious disorder, sometimes triggering dysthymia or clinical depression. It may require hospitalization.
Various etiologies have been suggested. One possibility is that SAD is related to a lack of serotonin and that exposure to full-spectrum artificial light may improve the condition by stimulating serotonin production although this has been disputed. Another theory is that melatonin produced in the pineal gland is the primary cause. There are direct connections between the retina and the pineal gland however some studies show that melatonin levels do not appear to differ between those with and without SAD. Light therapy appears to be effective in treating SAD, but the exact mechanism of the effect is still unknown.
Full Spectrum bulbs and "sunlight lamps" can be purchased as speciality lighting products for those suffering from SAD.
One recent trial seemed to indicate that shining a bright light behind the sufferers' knees would be beneficial, but when the trial was duplicated on a larger scale, the results were negative.
Medication is a more recent treatment and selective serontonin reuptake inhibitors (SSRI's) have proven effective in treating SAD. Examples of these antidepressants are fluoxetine (Prozac), sertraline (Zoloft), or paroxetine (Paxil).
Winter depression (or winter blues) is a common slump in the mood of Scandinavians. Doctors estimate that about 20% of all Swedes are affected, and it seems to be hereditary. It was first described by the 6th century Goth scholar Jordanes in his Getica where he described the inhabitants of Scandza (Scandinavia).
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