Seasonal Affective Disorder (SAD) is a form of depression with symptoms that come and go with changes in seasons. The most recognized form of SAD is “winter depression,” characterized by episodes of depression during the winter months that go away during warmer months.

The prevalence of winter-type seasonal affective disorder appears to vary with latitude. The higher the latitude, the more common the disorder. In addition, younger people and women are at higher risk for winter depressive episodes.