Seasonality of suicide attempts: association with gender.

Some studies suggest seasonality of suicide attempts in females, but not in males. The reasons for this gender difference remain unclear. Only few studies addressed the question whether gender differences in seasonality of suicide attempts reflect gender differences in the choice of method for suicide attempts, with inconsistent results. So, this study aimed to analyze the association of gender with seasonality in suicide attempts by persons living in two Northern Bavarian regions [city of Nuremberg (480,000 inhabitants) and region of Wuerzburg (270,000 inhabitants)] between 2000 and 2004. We addressed this question by focussing on the frequency of suicide attempts in relation to the seasons. The sample consisted of 2,269 suicide attempters (882 males and 1,387 females). The overall seasonality was assessed using the chi(2) test for multinomials. Moreover, the ratio of observed to expected number of suicide attempts (OER) with 95% confidence intervals within each season was calculated. As a result, overall distribution of suicide attempts differed significantly between seasons for women (chi(2) = 9.19, df = 3, P = 0.03), but not for men. Female suicide attempts showed a trough in the spring (decline compared to the expected value by 10%; OER = 0.9, 95% CI = 0.8-1.0). This trough was restricted to female low-risk suicide attempts (decline by 13%; OER = 0.87, 95% CI = 0.77-0.98). No seasonality was found for men. Seasonality of high-risk methods was more pronounced than that of low-risk methods; however, no significant gender differences were found concerning this aspect. The overall distribution of the sub-types of suicidal acts (parasuicidal gestures, suicidal pauses, suicide attempts in the strict sense) showed seasonality neither for males nor for females. Whereas seasonality was absent in male suicide attempters, the frequency of low-risk suicide attempts in females was 13.1% lower than expected in the spring.