Is hypersomnolence a feature of seasonal affective disorder?

We examined hypersomnolence as experienced among individuals meeting standardized diagnostic criteria for Seasonal Affective Disorder (SAD). Data were available from 115 individuals attending a mood disorders clinic specializing in treatment of this disorder. Three modes of assessment were employed: retrospective self-reports (Seasonal Patterns Assessment Questionnaire), cross-sectional interviews (Standardized Interview Guide for the Hamilton Depression Scale, SAD Version), and prospective sleep diaries. Results indicated that self-reported total hours of sleep varied significantly across the seasons, with longest sleep occurring in winter and shortest sleep in summer. Seasonal sleep changes, as indicated by the SPAQ did not correlate significantly, however, with severity of depressive symptoms as indicated by the Hamilton scale. Multiple regression analyses indicated that only social activity levels (one of seven SPAQ items) was significantly and uniquely related to the severity of depression. When data obtained by the three instruments were compared, self-reported hours of sleep (whether measured by SPAQ or Hamilton interview) were significantly higher than indicated by prospective sleep diaries. We conclude that hypersomnolence may not be a central feature of SAD and that the validity of the SPAQ as an index of this disorder requires further investigation.