Seasonal variation in suicide: is there a sex difference?

Seasonal variation in suicide in Italy for the years 1969-81 has been assessed in males and females by means of harmonic analysis. Cyclical fluctuations in the number of suicides, reasonably consistent over the 13 years of the study, have been observed in both sexes. Seasonal harmonics accounted for 65.3 and 48.4% of the variance in male and female suicides respectively. While in males the only important seasonal harmonic was the first (one cycle per year), in females there was an important first harmonic and a second harmonic (two cycles per year). In both sexes the peak of the first harmonic occurred in May, while in females the subsidiary peak occurred in October-November.