Seasonality of suicide: relationship with the reason for suicide

AIMS: This study set out to test the hypothesis that the suicides that can be attributed to a psychiatric illness show a higher seasonality than the suicides due to any other reason. METHODS: All the suicides registered in Italy from 1984 to 2000 (57,796 deaths by suicide: males = 41,741, yearly rate = 11.3 per 100,000; females = 16,055, yearly rate = 4.0 per 100,000) were analyzed with circular statistic techniques, based on the maximization of mean vector length method and on the Rayleigh test. RESULTS: The suicides clearly attributed to a psychiatric illness were 35.0% among males and 51.3% among females. An economic reason for suicide was more frequently found among males; somatic illness or sentimental reasons were equally distributed in both sexes. The suicides attributable to a psychiatric illness showed a significantly higher seasonal unevenness than the suicides attributable to somatic illness and to sentimental or economic reasons. CONCLUSIONS: The main drawback of this study is that psychiatric diagnoses were not formally assessed by a forensic specialist. However, it succeeded in showing that the dynamics of suicidal behaviour are not unilineal: suicides due to psychiatric or somatic illness mainly happen in spring/summer and those due to economic difficulties mainly in December. Patients with psychiatric and/or somatic illness should be more carefully followed in spring/summer.