A nationwide survey of seasonal affective disorder at 53 outpatient university clinics in Japan.

A nationwide survey of seasonal affective disorder (SAD) was performed from autumn 1990 to spring 1991 with the cooperation of 53 outpatient university psychiatric clinics in Japan. Forty-six SAD patients were identified among 5265 depressed outpatients. SAD was generally reported to occur in 1-3% of the depressed outpatients newly attending each facility. Hours of sunshine were found to be a more relevant variable influencing the prevalence of SAD than latitude or the mean temperature in December. The unexpectedly low percentage (20-30%) of SAD patients with atypical vegetative symptoms suggests that SAD patients who have no prior knowledge of SAD and those who are recruited via the media have different vegetative symptom profiles.