Long-term follow-up of depression in seasonal affective disorder.

Twenty-six patients diagnosed as having seasonal affective disorder (SAD) completed weekly depression self-ratings for at least 2.5 and up to 8.25 years. Seasonal recurrence of depression persisted in nine patients, seven remitted, four were chronically depressed, and six showed a diffuse pattern. The age at SAD onset and duration of SAD history before entry into this prospective study could not be identified as predictors of the subsequent course of the disease. Short-lasting, recurrent periods of depression could be identified in many of the long-term records. They were found primarily in autumn and winter in patients with either a persistent seasonal or a remitted pattern. In the core group of patients with persistent seasonal pattern, the onset and offset of depressive periods (DPs) were more variable than the DSM-III-R 60-day window criterion for seasonal pattern allows.