Seasonal Affective Disorder is a Major Depressive Disorder experienced by people who have normal mental health throughout most of the year, but experience depressive symptoms in the winter or, less frequently, in the summer, spring or autumn, repeatedly, year after year. Usually, seasonal affective disorder symptoms appear during late fall or early winter and go away during the sunnier days of spring and summer. Some people have the opposite pattern and become depressed with the onset of spring or summer. In either case, problems may start out mild and become more severe as the season progresses.
Just as sunlight is known to affect the seasonal activities of animals (i.e., reproductive cycles and hibernation), SAD is believed to be an effect of seasonal light variation in humans. As the seasons change, it is suggested that there is a shift in the “biological internal clocks” or circadian rhythm, due partly to these changes in sunlight patterns. It is this shift that is believed to cause the biological clocks to be out of “step” with the daily schedule, resulting is Seasonal Affective Disorder.
Symptoms for SAD are similar to those for atypical depressive illness such as hypersomnia (increased sleep), increased appetite with carbohydrate cravings, weight gain and profound fatigue. Younger individuals, particularly women, appear to be at higher risk for SAD.
Researchers have long sought to locate the biochemical sources of this disorder. It has been discovered that the pineal gland, located in the middle of the brain, responds to darkness by secreting melatonin, which re-sets the brain's central clock and helps the light/dark cycle re-set the sleep/wake cycle and other daily rhythms. To further evaluate this, researchers (Lewy et al, 2006) tracked sleep, activity levels, melatonin rhythms and depression symptoms of 68 SAD patients who took either low doses of melatonin or a placebo in the morning or afternoon for a winter month when they were most symptomatic. They had previously determined from healthy subjects that a person's rhythms are synchronized when the interval between the time the pineal gland begins secreting melatonin and the middle of sleep is about 6 hours. They found that seventy-one (71) percent of the SAD patients had intervals shorter than 6 hours, indicating that their rhythms were delayed due to the later winter dawn. Taking melatonin capsules in the afternoon lengthened their intervals, bringing their rhythms back toward normal. The closer their intervals approached the ideal 6 hours, the more their mood improved on depression rating scales, supporting the hypothesized link between out-of-sync rhythms and SAD.
Apart from melatonin supplements, treatment for SAD also includes bright light treatment. For this treatment, the person is required to sit in front of a "light box" for half an hour or longer, usually in the morning. Another useful treatment is called dawn simulation. For this treatment, a dim light goes on in the morning while the person sleeps, and it gets brighter over time, like a sunrise. Treatment for SAD can also include antidepressants which have been shown to be effective in the treatment of SAD. Finally, psychotherapy, in conjunction with the above, has resulted in improved overall coping for sufferers of SAD.
Those believed to be suffering from SAD should seek professional consultation to obtain an accurate diagnosis and to rule out other causes for the depressive symptoms.