Seasonality of mania in New Zealand.

This paper examines the seasonal variation in manic admissions over a five year period in New Zealand. There is a significant monthly variation in admission rates with a spring/summer peak. Breakdown by sex, age and admission status suggested that there is no particular subgroup responsible, but that young first admissions and older female readmissions do not follow this trend. Examination of the monthly admission rates revealed that this peak is not constant from year to year. Possible mechanisms, which link fluctuating environmental variables with an irregular spring/summer peak for manic admissions, are discussed.