To report on the prevalence of seasonal bipolar disorder (BD) and the impact of latitude in a community sample in the province of Ontario.
This study used the telephone-administered Depression and Seasonality Interview. Exact latitude was determined for each participant.
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.
We identified a seasonal pattern of illness in a proportion of subjects with BD.