Heat does not do the body good. Anyone who has been sunburnt or dehydrated knows this all too well. But with massive record-breaking heat waves forcing outdoor summer plans indoors, we are rapidly reckoning with exactly how bad extreme temperatures are for us.
As temperatures spike, the body’s cardiovascular system gets a stress test. Studies show the risk of heart attacks elevates during hotter weather, especially when you throw bad air quality into the mix. When high temperatures combine with high humidity, heat-related illnesses like heat exhaustion and stroke increase. And when temperatures hover in the triple digits, wildfire risk increases, along with the resulting particulate pollution, which can cause breathing difficulties and asthma in susceptible people.
But excessive heat also threatens an often overlooked aspect of our lives: mental health. Emerging research suggests extreme heat could be increasing rates of stress, anxiety, behavioral issues, and other mental health conditions.
What the studies show
A 2022 study in JAMA Psychiatry found that ER visits involving a mental health condition increased during hotter summer days compared to cooler ones. The study looked at data from nearly 3.5 million ER visits across the U.S. between 2010 and 2019.
“We saw overall emergency department visits increasing, but we also specifically saw increases in rates of visits from stress and anxiety, and for schizophrenia, substance use disorders, somatoform disorders, mood disorders, and self-harm,” Amruta Nori-Sarma, an assistant professor of environmental health and Boston University School of Public Health, told Rolling Stone. “These mental health endpoints don’t really have a lot of relationship to each other, which indicates that heat is likely an external stressor that’s exacerbating people’s pre-existing symptoms.”
In a July 2023 analysis in the journal The Lancet Planetary Health, researchers found that even a one degree increase in ambient temperature above the norm contributed to a higher probability of experiencing depression and anxiety.
Undiagnosed and untreated mental health can lead to far worse consequences in the face of sweltering temperatures. A 2018 study published in Nature Climate Change found that a 1.8 degree Celsius increase in average temperature across the U.S. and Mexico correlated with a 0.7 percent increase in suicides, a trend the paper’s authors said would only worsen as temperatures continue to climb.
“We project that unmitigated climate change could result in a combined [nine thousand to forty] thousand additional suicides… by 2050, representing a change in suicide rates comparable to the estimated impact of economic recessions, suicide prevention programs or gun restriction laws,” they wrote.
More recently, a 2021 analysis published in the journal Environment International also came across similar findings. Looking at over 50 studies on heat exposure and mental health outcomes between 1990 and 2020, the researchers saw that during heat waves, for every one degree Celsius increase, there was a 0.9 percent increase in hospital admissions and emergency room visits for mental health conditions. There was also a 2.2 percent increase in mental health-related deaths.
Why would heat worsen mental health?
The how and why of heat screwing with our mental health isn’t entirely clear. For some vulnerable groups, including those with pre-existing mental health conditions, their psychiatric medications or other comorbidities may affect the way their bodies can regulate heat, according to the American Psychiatric Association.
Seasonal affective disorder (or SAD), which is often associated with not enough sunlight during fall and winter, can also happen during the summertime. In this case, too much sunlight, heat, and humidity are believed to disrupt chemicals that regulate mood, such as norepinephrine, serotonin, and dopamine, which are linked to regulating body temperature, according to The New York Times.
Extreme heat can also affect how well we sleep, which in turn affects our mental health. Studies show that when temperatures become unseasonable, sleep quality plummets. When you’re not getting a good night’s shut-eye, this leads to a plethora of deleterious health issues such as memory loss, mood changes, and an inability to focus, not to mention an increased risk for depression, heart attack, stroke, and diabetes.
Will it get worse?
With heat waves expected to become more common as the climate crisis remains unabated, the implications for mental health warrant further spotlighting and more study, Josh Wortzel, a psychiatrist at Brown University studying climate change and mental health, told Time.
“Climate change is now considered the number-one public health concern. But there is not enough understanding of how it impacts mental health,” said Wortzel. “For us to not be investing more right now in how to understand the impacts of heat on the brain is unfortunate.”
