Temperature change dominates the suicidal seasonality in Taiwan: A time-series analysis

Objective: The arguments between bioclimatic and sociodemographic hypotheses for the suicidal seasonality continue. The present study aimed to examine the relationships between suicidal seasonality and the climate as well as the economic factors. Methods: The monthly suicide death rates of the total, male and female populations in Taiwan during January 1991-December 2010 were obtained from the population-based database. Autoregressive integrated moving average (ARIMA)/seasonal ARIMA (SARIMA) was used to analyze suicidal seasonality, with monthly ambient temperature, temperature increase, rainfall, sunlight, unemployment and labor force participation rates as the independent inputs. Results: The models revealed that monthly temperature increase was strongly positively associated with seasonality of suicide rates of all populations (beta=0.0184, P<0.001; beta=0.0234, P=0.001; beta=0.0145, P<0.001, respectively). Rainfall was significantly negatively associated with the total and male suicide rates (beta=-0.0001, P=0.012; beta=-0.0002, P=0.043, respectively), but not with female. Unemployment and labor force participation rates were not significantly related to their corresponding suicide rates. Limitations: Socio-demographic data, individual major events, and subgroups by suicide methods were not taken into account. Conclusions: The results indicate that, as far as suicidal seasonality is concerned, monthly temperature increase is the most influential factor, and climatic factors have more significant effect than the economic factors. (C) 2011 Elsevier B.V. All rights reserved.