Seasonal affective disorder.

Seasonal affective disorder (SAD) is a recently described mood disorder characterized by recurrent winter depressive episodes and summer remissions. The symptoms of SAD include DSM III-R criteria for recurrent major depression, but atypical depressive symptoms predominate with hypersomnia, hyperphagia and carbohydrate craving, and anergia. Seasonal affective disorder is effectively treated by exposure to bright light (phototherapy or light therapy), a novel antidepressant treatment. The authors review the syndrome of SAD, hypotheses about its pathophysiology, and the use of phototherapy to treat the disorder.