As far as summers go, this one has been particularly hot and humid. Record-breaking temperatures have been recorded all across the Northern Hemisphere, and the result has been deadly. The heat wave that hit Canada earlier this month led to at least 54 deaths, with the elderly most affected. Japan’s heatwave has been so intense that the government weather agency has declared it a natural disaster. On Monday, the city of Kumagaya hit 105.98 degrees Fahrenheit, its highest-temperature ever since records first began in the 1800s, and an even higher one has been recorded in the hottest inhabited place on Earth. The scorching weather has killed at least 77 people and sent 300,00 more to the hospital.
When newspapers report heat-related illnesses, they are usually referring to heat cramps, heat exhaustion, and heat stroke. But according to a disturbing new study published in in Nature Climate Change, there’s one type of death caused by scorching temperatures that experts have yet to take into account: suicide.
Researchers compared the temperature and suicide rates of Mexico and the U.S. (both of which have experienced abnormally hot weather this summer) over decades and found a concerning link between hotter weather and suicide. To be more specific, they found that “suicide rates rise 0.7% in U.S. counties and 2.1% in Mexican municipalities for a 1 °C increase in monthly average temperature.”
That might sound small, but the paper predicts with relative certainty that if temperatures continue to climb, it could lead to up to 40,000 additional suicides across the U.S. and Mexico alone by 2050.
It’s long been known that seasonal patterns affect suicide rates, but much of the research has focused on how cold weather affects people’s moods, especially as the result of low exposure to sunlight and seasonal affective disorder.
But this study indicates that the other extreme—scorching temperatures—has a similarly negative impact on mental health. The study also analyzed over 6 million tweets within the U.S. and found that depressive language, such as lonely,” “trapped” or “suicidal,” spikes when temperatures rise. For each one degree Celsius rise in temperature, the likelihood of a tweet containing depressive language rose by 0.79 percent. This may not be altogether surprising, as a previous study confirmed that extremely hot weather does, in fact, inhibit your ability to think straight.
Since most scientists predict temperatures will continue rising as a result of the emission of carbon dioxide, methane, and other greenhouse gases, this finding is extremely concerning.
“We’ve been studying the effects of warming on conflict and violence for years, finding that people fight more when it’s hot,” said Solomon Hsiang, an associate professor at the University of California, Berkeley and co-author of the study.
Marshall Burke, a professor of Earth system science at Stanford and co-author of the study, emphasized that “hotter temperatures are clearly not the only, nor the most important, risk factor for suicide,” but noted that their results remained largely the same even when factoring in gun ownership, sex, population size, average income, or the availability of air-conditioning.
“Studies suggest that some components of brain chemistry, in particular certain neurotransmitters, are important in both mental health and in how the body regulates its internal temperature,” Burke told CNN. “That to us suggests at least there’s a plausible biological linkage between temperature, thermal regulation and how the brain regulates its own emotion.”
For more on suicide prevention, read about these 20 People Who Nearly Committed Suicide—and What Stopped Them.
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