Secular trends in the rates and seasonality of violent and nonviolent suicide occurrences in Finland during 1980-95

Background: Because secular trends in seasonality of different types of suicides has not been studied before, we utilized a novel statistical method to evaluate this phenomenon by using national Finnish suicide statistics during 1980-95. Methods: Rates were analyzed with ordinary linear regression analysis. Secular trends were evaluated using ratio-statistic and its 95% confidence intervals. Results: The rate of violent suicides increased before year 1990 and decreased since that. The nonviolent suicide rate increased continuously. The decreasing tendency of seasonality in nonviolent suicides and a slight decrease in violent suicides are seen within the three successive time periods studied. Conclusions: Trends in rates and in seasonality of suicides might be related to changes in the health politics in Finland. Limitations: The short time-series and lack of studying associations of suicides with socioeconomic, environmental or biological factors are limitations of our study. Clinical relevance: Studying the time-dependent changes in rates and in seasonality of suicides provide a novel perspective for the evaluation of the aetiology of suicidal behaviour. (C) 1998 Elsevier Science B.V.