How heat waves harm mental health

NEW YORK — Tens of millions of people across the United States have endured heat wave after heat wave this summer, in what feels like a relentless succession of humid days and scorching temperatures. While it’s undeniable that extreme heat and humidity can be physically uncomfortable, research suggests that such conditions can also negatively affect your psychological well-being.

“We are seeing across the mental health spectrum” that extreme temperatures are detrimental to mental well-being, said Dr. Nick Obradovich, social scientist in computing at the Max Planck Institute for Human Development and co-author from a 2018 study that analyzed the mental health risks of climate change.

Studies have linked rising temperatures to a range of mental health issues, including mental fatigue, aggression and even higher suicide rates. This connection isn’t just limited to temperature spikes, Dr. Obradovich said, it’s also present for people living in climates where it’s consistently hot. (Although, of course, trends in mental health can also depend on various factors besides temperature.)

Scientists have yet to find out why this might be and whether the heat itself can cause brain changes that can lead to these effects. But regardless, experts say, it’s clear that oppressive heat is linked to poorer mental health.


Evidence suggests that “extreme temperatures can influence everything from your daily mood to your likelihood of experiencing an acute mental health crisis,” Dr Obradovich said.

A study published in JAMA Psychiatry in February, for example, examined the medical records of more than 2.2 million adults who visited emergency departments in 2,775 counties across the United States between 2010 and 2019.

The authors found that there were about 8% more emergency room visits for mental health issues on the hottest days of summer than on the coolest days. Emergency room visits for issues such as self-harm, as well as substance abuse, anxiety, mood and schizophrenia disorders, all rose steadily in proportion to temperature.

This trend is “fairly consistent for men and women, for adults of all ages, and for people living in all parts of the United States,” said Dr. Amruta Nori-Sarma, an environmental health scientist at the Boston University School of Public Health and a study author.

Other research has also shown that higher temperatures can temporarily trigger relapses in people with bipolar disorder, and higher sun exposures can increase the risk of manic episodes. Higher temperatures have also been linked to deaths in people with schizophrenia and other mental health conditions.

Data from a survey of 1.9 million Americans between 2008 and 2013 found that on days with temperatures above 21°C, respondents were more likely to experience reduced joy and happiness, as well as an increase in stress, anger and fatigue, than on days with high temperatures. between 10°C and 15.5°C degrees. These associations were particularly strong when temperatures were above 32°C, the authors noted.


“When we’re not comfortable, we’re not at our best,” said Dr. C. Munro Cullum, a clinical neuropsychologist at UT Southwestern Medical Center in Dallas. Heat discomfort and the energy needed to cool the body can reduce overall resilience. Thus, the restlessness, irritation and pain become less bearable, he says.

Our bodies are also used to some baseline level of stress, said Dr. Martin Paulus, chief scientific officer and president of the Laureate Institute for Brain Research in Tulsa, Oklahoma, who worked with Dr. Obradovich on his 2018 study.

When the body tries to regulate its temperature during a heat wave, he says, it adds extra tension and leads to more stress and inflammation. People with pre-existing mental health conditions may be particularly vulnerable to additional heat stress, which can worsen their symptoms, he said.

As for what happens in the brain during extreme heat, that’s hard to study, Dr. Paulus said. In a lab, you can experience how the brain and the rest of the body can withstand minutes or possibly hours of high temperatures, but you can’t do it for days, weeks or months at a time – and that it’s these longer exposures that are really important for understanding how climate change may affect us in the long term.

But the fact that this link between heat and mental health is so consistent in people around the world suggests that heat is doing something to the brain, Dr. Nori-Sarma said. Some researchers have speculated that heat may cause an imbalance in brain signaling or inflammation in the brain. But another prominent theory is that heat causes sleep disruptions, which in turn can worsen mental health symptoms.

Hot nights make sleep significantly worse, Dr. Obradovich said. “And we know from a large number of publications in psychology and psychiatry that lack of sleep, sleep difficulties and insomnia are very strongly linked to a deterioration in mental health over time. .”

It’s possible that the explanation for the effect of heat on mental health comes from a combination of these different existing theories, Dr. Obradovich added.


Nor can we forget about climate anxiety, said Dr. Paulus. Wildfires and heat waves, among other weather-related events, are increasing in frequency and intensity due to climate change. As global warming worsens, eco-anxiety could exacerbate other symptoms of disaster-related stress, anxiety, depression or even post-traumatic stress, he added.

Some people are also more vulnerable to heat than others. In their 2018 study, Dr. Obradovich and Paulus’ team found that low-income people experienced more severe mental health effects from heat than those with higher incomes, and women experienced worse effects. only men. Together, they found that the effect of heat on mental health was twice as detrimental for low-income women as for high-income men.

In the middle of a heat wave, we don’t always know how to protect ourselves. But being aware of your heat exposure, staying hydrated, and avoiding the heat when you can are always good options. Caring for the people in your community is also a powerful and overlooked strategy, Dr. Nori-Sarma said.

It means “neighbors check in on neighbors, friends and families, make sure everyone is okay.”

This article originally appeared in The New York Times.

Comments are closed.