Influence of Season and Latitude in a Community Sample of Subjects with Bipolar Disorder

OBJECTIVE: To report on the prevalence of seasonal bipolar disorder (BD) and the impact of latitude in a community sample in the province of Ontario. METHOD: This study used the telephone-administered Depression and Seasonality Interview. Exact latitude was determined for each participant. RESULTS: Overall, 14 of 62 (22.6%) subjects with BD had the seasonal subtype of BD. Latitude did not appear to influence the proportion of subjects with the seasonal subtype. CONCLUSIONS: We identified a seasonal pattern of illness in a proportion of subjects with BD.