Seasonality of manic depressive illness in Canada

Objective: The objective of the study was to determine if a seasonal pattern existed for hospital admissions of manic depressive illness to a Ontario provincial psychiatric hospital. Method: Admission records were reviewed for the 75 year period of the study. In the analysis factors including: mood state on admission, gender and the influence of psychotropic medications were considered. Results: For mania and depression there was no statistically significant seasonal pattern of admissions. For mixed state admissions peaked in the summer. Conclusions: The results of this study contradict the seasonal pattern traditionally reported in the literature. The limitations of this study, which include changes in diagnostic criteria over time and admission date not identical to onset of affective episode, need to be acknowledged.