As Global Temperatures Increase, So Could Rates of Deaths by Suicide

In nonoptimal, extreme high heat, it has been predicted that deaths by suicide would increase as the temperature rises. These results from a study were published in JAMA Psychiatry.

This study was conducted by investigators at Fudan University in Shanghai, China. Data were sourced from the China Cause of Death Reporting System and the European Centre for Medium-Range Weather Forecasts Reanalysis Fifth Generation (ERA5) database. Records of deaths by suicide between 2013 and 2019 were related with daily mean temperatures. Three historic and future temperature scenarios (socioeconomic pathway [SSP] scenarios SSP126, SSP145, and SSP585) were projected using greenhouse-gas emissions data from 1980 to 2099. Suicide deaths were predicted as a function of average temperatures.

A total of 432,008 decedents were included in this analysis. Decedents were mean age 57.6 (SD, 19.0) years, 58.6% were men, and 85.8% had obtained a middle school education or less.

Across all suicide locals, the average temperature was 13.6°C (SD, 11.2°C), which was highest in the South (mean, 21.6°C) and lowest in the Northeast (mean, 6.2°C).

Higher temperature could increase the risk and burden of suicide death.

When the extreme high temperature (30.9°C) was compared with the minimum temperature (-17.4°C), national suicide risk increased ([RR], 1.44; 95% CI, 1.34-1.54). This relationship indicated that for every 1°C elevation in temperature, suicide risk increased by 0.91%. Stratified by region, the risks were higher in the Northeast, Northwest, Southwest, North, and South than national rates.

Stratified by subgroup, the risk for suicide in extreme high heat was higher among individuals aged 75 years and older (RR, 1.71; 95% CI, 1.46-1.99), with lower levels of education (RR, 1.46; 95% CI, 1.36-1.57), and men (RR, 1.47; 95% CI, 1.35-1.60) compared with women (RR, 1.39; 95% CI, 1.25-1.55).

The most prominent climate change scenario was SSP585 which predicted a 5.5°C increase by the 2090s, followed by SSP245 (mean difference [MD], 3.0°C) and SSP126 (MD, 2.0°C). In all scenarios, the difference in temperature became more apparent after the 2050s.

Compared with historic scenarios, investigators predicted that deaths by suicide would increase by 2.3%-2.6% in the 2010s, by 8.3%-11.4% in the 2050s, and 8.5%-21.7% in the 2090s. Under the worst-case scenario, there will be 24,214 excess deaths by suicide in 2090 and under the best-case scenario, 9429 excess deaths by suicide. These rates differed by geography and season.

These findings may not be generalizable outside of China and these predictions were based on current socioeconomic conditions in China, which may not be generalizable for the future.

Study authors concluded, “[H]igher temperature could increase the risk and burden of suicide death. Findings further suggest that climate warming may lead to significant increases in future burden of suicide death associated with nonoptimum temperature, especially in the high-emission scenario.”