Suicide and Heat
Robin Cooper, MD
Aug. 3, 2018
Suicide deaths have received a lot of public and professional attention with the recent publication by the Centers for Disease Control (1) of an unprecedented 30% increase in the US between 2000 and 2016; and the recent suicide deaths of celebrities Kate Spade and Anthony Bourdain. To add to the complexity, there is startling new information about the link between heat and suicide published in Nature Climate Change, (July 2018.) (2) This is something about which all psychiatrists should take note, since suicide is one of the top causes of death in the US and worldwide.
The authors of this study report that a 1 degree Celsius increase in average monthly temperature increased suicide rates 0.7 % in USA and 2.1% in Mexico. In a separate interview, the lead author (Marshall Burke from Stanford University) acknowledges the multifaceted contribution to suicide. (2) However, this new study is remarkable and stands out from other previous studies reporting linkage between heat and suicide by controlling for a multitude of confounding variables. These include gender, time of year, rural or urban residence, regional poverty and income levels, location effects such as daylight exposure, gun availability and access to air-conditioning.
This is the first study looking at rates in North America; other briefer reports linking climate change to suicide have had more limited scope and have looked at rural farmers in India and in Australia.
The effects described in the Burke study hold true whether in cooler or hotter climates, and over decades, indicating that there is no adaptation to warming temperatures over time. The authors highlight the improvement in general health impacts with economic development (lessened environmental exposures, greater access to air-conditioning) but find no such adaptation for the relationship between increased temperature and suicide. According to the author: “Even once you control for income, you still don’t see air-conditioner use come through as a factor. Suicide is a fundamentally different animal than these other types of mortality, like cardiac mortality, that you see in the literature.”(3)
In addition to reviewing suicide data, the authors analyzed over 600 million social media communications and found an increase in depressive language and suicidal ideation correlated with increased temperatures - indicating a decrease in mental well-being.
Given their results, the authors make a startling projection about the future impacts of climate change and global warming. They estimate that by 2050, assuming no reduction in green house gas emissions, there will be 14,020 excess suicides in the US and 7,460 excess suicides in Mexico. They suggest these rates are comparable to the effects on suicide incidence due to economic recessions and unemployment, celebrity suicides, gun restriction laws and suicide prevention programs.
This study, along with related research that indicates an increase in violence with temperature increases (4), is an important observation regarding the impact of heat on human behavior. Although the underlying biological and physiological mechanisms remain to be elucidated, there is some speculation on the role of serotonin (3). Additional research is clearly needed. However, the authors leave with a final call for implementing “policies to mitigate future temperature rise”.
The urgency to control climate change is clear; we must use all of our leverage to limit global warming and advocate for policies that protect our communities and promote mental well-being.
1: Stone, D. et al. Vital Signs: Trends in State Suicide Rates-United States, 1999-2016 and Circumstances Contributing to Suicide -27 States 2015; Morbidity and Mortality Weekly Report, June 8, 2018/67(22):617-624 https://www.cdc.gov/mmwr/volumes/67/wr/mm6722a1.htm?s_cid=mm6722a1_w
2: Burke, M, et al. Higher Temperatures increase suicide rates in the United States and Mexico. Nature Climate Change. July 23,2018/8/723-729.
3. Meyer, R. Climate Change May Cause 26,000 More U.S. Suicides by 2050. The Atlantic. July 23, 2018.
4. Burke, M. et al. Climate and Conflict. Annual Review of Economics. Aug., 2015. Vol 7:577-817