Seasonal affective disorder, or SAD, is a type of depression that affects a person during the same season each year. If you get depressed in the winter but feel much better in spring and summer, you may have SAD.
Anyone can get SAD, but it is more common in:
Experts are not sure what causes SAD, but they think it ma y be caused by a lack of sunlight. Lack of light may upset your sleep-wake cycle and other circadian rhythms. And it may cause problems with a brain chemical called serotonin that affects mood.
If you have SAD, you may:
Symptoms come and go at about the same time each year. For most people with SAD, symptoms start in September or October and end in April or May.
It can sometimes be hard to tell the difference between nonseasonal depression and SAD, because many of the symptoms are the same. To diagnose SAD, your doctor will want to know if: