Burke and his colleagues analyzed comprehensive mortality data from multiple decades for the U.S. and Mexico, two countries that account for roughly 7 percent of the world’s suicides. By interpolating monthly temperature and precipitation data from Mexico’s Instituto Nacional de Estadística y Geografía, the U.S. PRISM climate dataset and from more than 10,000 U.S. weather stations, the researchers established models to estimate the displacement effects of hot temperatures on future suicides.
They also studied depressive language in social media by collecting geo-located Twitter data to study how temperatures increase the likelihood of using specific depressive keywords in tweets.
Using 30 global climate models on future climate projection, the researchers then combined their historical estimates of the effect of temperature on suicide to estimate the potential increase in suicide rate due to warming by 2050.
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According to the robust projection data, study authors predict that approximately 14,000 people in the U.S. — and as many as 26,000 — could die by suicide by the year 2050 if global temperatures continue rising, even after controlling for every other major variable that could affect suicide rates.
If monthly temperatures are 1 degree Celsius warmer than usual, researchers estimate suicide rates in the U.S. will increase by 0.7 percent and by 2.1 percent in Mexico.
“‘Climate change is going to generate winners and losers’—this is a phrase you hear all the time,” Burke said. “But for this outcome, it’s all losers. There are no winners. We find these strong linear relationships everywhere when you crank up the temperature.”
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The researchers did not make conclusions regarding specific underlying mechanisms behind the climate-suicide relationship, but they addressed previous science revealing how thermoregulation and other neurological responses to high temperature directly alter the mental well-being of individuals — and depressive disorders are implicated in more than half of all suicides.
Previous research from the Harvard T.H. Chan School of Public Health has also found that people suffering through the heat tend to have decreased cognitive function.
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Unlike other causes of mortality due to temperature, “suicide increases at hot temperatures and decreases at cold temperatures,” authors of the Nature study wrote. Additionally, “the effect of temperature on suicide has not decreased over time and does not appear to decrease with rising income or the adoption of air conditioning.”
According to the findings, the projected effects of climate change on suicide rates by 2050 are “two to four times the estimated effect of a 1% increase in the unemployment rate in the European Union” and “roughly one-third as large in absolute magnitude (with opposite sign) as the estimated effect of gun restriction laws in the United States.”
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“The large magnitude of our results adds further impetus to better understand why temperature affects suicide and to implement policies to mitigate future temperature rise,” authors concluded.
Read the full study at nature.com.
Last year was Georgia's warmest year ever with a record mean temperature of 65.8 degrees, according to state climatologist Bill Murphey. The majority of the country also witnessed above average temperature ranks in 2017.
The country also experienced a nearly 30 percent increase in suicide rates between 1999-2016, according to the Atlanta-based Centers for Disease Control and Prevention.
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Between 1996 and 2016, Georgia experienced a 16.2 percent increase in suicide rates, comparatively low among the 25 states where suicide rates rose by nearly 30 percent. But that’s still considered a significant increase, according to the CDC.
If you or anyone you know is contemplating suicide, or if you are concerned for someone else, here are some helpful resources:
National Suicide Prevention Lifeline (24 hours)
Suicide prevention resources for parents, guardians and families
Suicide prevention resources for teens
Suicide prevention resources for survivors of suicide loss
More resources and programs at the Suicide Prevention Resource Center.