Seasonal affective disorder

Definition:

A form of depression that recurs with a fall-winter onset and a spring-summer remission (also known as SAD).

Causes, incidence, and risk factors:

The cause of seasonal affective disorder (SAD) is not known, but is thought to be related to the body's temperature and hormone regulation. The disorder is rare, and most people with the "winter blahs" or cabin fever do not have SAD. The disorder may have its onset in adolescence or early adulthood, and it occurs more frequently in women than in men.