Depressive episodes are common . Approximately 10 to 40 percent of patients in primary care settings have clinically significant depressive symptoms, although less than one-half meet the criteria for unipolar major depression . Some of these depressive episodes tend to follow regular seasonal patterns, consistently occurring at particular times of year. These seasonal mood patterns have been termed seasonal affective disorder (SAD).
This topic reviews the epidemiology, pathogenesis, clinical features, diagnosis, and treatment of SAD. The clinical features, diagnosis, treatment, and prognosis of nonseasonal major depression are discussed separately.
●(See "Clinical manifestations and diagnosis of depression".)
●(See "Unipolar major depression in adults: Choosing initial treatment".)
●(See "Unipolar depression in adults: Treatment of resistant depression".)