Seasonality of mania: a reappraisal.

Some recently published data on the seasonal incidence of mania are re-examined. The reanalysis confirms a strong, seasonal trend in females, but also demonstrates a similar trend in males; the latter results is at variance with an earlier finding which showed no seasonal pattern in males. A simple harmonic curve would describe the data extremely well in both sexes, and the parameters of these curves (the amplitude of variation and the time of maximum incidence) are very close for males and females.