Temperature-associated suicide mortality: contrasting roles of climatic warming and the suicide prevention program in Finland

Abstract

Objectives: Suicide is a notable cause of death worldwide, and while suicidal behavior appears to be associated with variations in temperature, no estimations are available of climate change impacts on suicide rates. The study aims to evaluate the influence of temperature on suicide mortality, especially on multi-decadal and longer time scales, that is, at scales on which the ongoing warming distinctly operates and is correspondingly appropriate for the current policy responses to warming climate.

Methods: Our results are based on an extraordinarily long record of deaths from suicide in Finland from 1751 to 2008, and a similarly long climatic record of ambient temperatures correlative of environmental change in the study region.

Results: We show that temperature variability explains more than 60 % of the total suicide variance up until the initiation of a national suicide prevention program. Despite ongoing warming, suicide rates have declined since the initiation of the program.

Conclusion: By understanding the complexity of suicidal behavior as a response to ambient warming and the observed effects of interventions, our results underline the pressing need for a network of prevention programs to battle against temperature-mediated health hazards.

Fig. 1

Suicide variations of the 1751–2008 period. Initial suicide rates (a) were calculated relative to population changes and their transformations (b) relative to the changing variance and non-linear trends. See Supplementary material (Table S1) for descriptive statistics of data. Z-score refers to the number of standard deviations from the long-term mean of the series

Fig. 2

Sensitivity of suicidal deaths to temperature fluctuations. Linear model quantifies the pre-program association using 15-year means of suicide rates and temperatures. Pearson correlations are shown both for the pre-program (r_P) (here, 1751–1990) and full (r_F) (here, 1751–2005) periods, with Monte Carlo [27] based statistical significance (P). Z-score refers to the number of standard deviations from the long-term mean of the series

Fig. 3

Temporal variations in suicides and temperatures. The values are shown between 1751 and 1990 using 30-year means with 10-year step. The associations between suicide rates and temperature were quantified using Pearson correlations (r) and the statistical significance (P) of each correlation. The calendar year indicates the last year of the 30-year period. The significance was generated using a Monte Carlo method [27] with a number of 1,000,000 surrogate series

Fig. 4

Temporal fluctuations in observed and modeled suicide figures. The model was built using the relationship established above (shown as black line in Fig. 2), with the Monte Carlo based [28, 29] confidence area, and the series transformed back to the original scale using the inverse of the transformations that were applied to the data