How heat waves affect mental health

NEW YORK — Tens of millions of people across the United States have endured heatwave after heatwave this summer in a seemingly inexorable succession of wet days and searing temperatures. While there’s no denying that extreme heat and humidity can be physically uncomfortable, research suggests such conditions can also affect your psychological well-being.

“We’re seeing across the mental health spectrum” that heat extremes are affecting mental well-being, said Dr Mental Health Risks of Climate Change.

Studies have found links between rising temperatures and a range of mental health problems, including mental exhaustion, aggression and even higher suicide rates. This connection isn’t just limited to temperature changes, said Dr. Obradovich, but also for people who live in climates where it is constantly hot. (Although, of course, mental health trends can also depend on a variety of factors outside of temperature.)

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


There is evidence that “temperature extremes can affect everything from your daily mood to your likelihood of experiencing an acute mental health crisis,” said Dr. Obradovich.

For example, a study published in JAMA Psychiatry in February examined the medical records of more than 2.2 million adults who attended emergency departments from 2,775 counties in the United States between 2010 and 2019.

The authors found that about 8 percent more emergency department visits for mental health issues occurred on the hottest days of summer than on the coolest days. Emergencies for problems such as self-harm, drug use, anxiety, mood swings, and schizophrenic disorders all increased in proportion to temperature.

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

Other research has also found that higher temperatures can temporarily trigger flare-ups in people with bipolar disorder, and that higher sun exposure could increase the risk of manic episodes. Higher temperatures have also been linked to deaths in people with schizophrenia and other mental illnesses.

Survey data of 1.9 million Americans between 2008 and 2013 found that respondents were more likely to feel less joy and happiness, and increased stress, anger and fatigue on days with temperatures above 21°C than on days with temperatures above 21°C between December 10 and 20 °C and 15.5°C degrees. These associations were particularly strong when temperatures were above 32 °C, the authors noted.


“If we’re not feeling well, we’re not at our best,” said Dr. C. Munro Cullum, a clinical neuropsychologist at UT Southwestern Medical Center in Dallas. The uncomfortable heat and the energy the body needs to cool down can reduce overall resilience. This makes the excitement, irritation and pain less tolerable, he said.

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

When the body tries to regulate its temperature during a heat wave, it adds extra strain and leads to more stress and inflammation. People with pre-existing mental illnesses might be particularly vulnerable to the added heat stress, which can exaggerate their symptoms, he said.

What happens in the brain during extreme heat is difficult to study, said Dr. Paul. In a lab, you can experiment with how the brain and rest of the body withstands high temperatures for a few minutes, possibly hours, but you can’t do it for days, weeks, or months at a time — and it’s those longer exposures that really matter are 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 among people around the world suggests heat is doing something to the brain, said Dr. Nori Sarma. Some researchers have hypothesized that heat may cause an imbalance in brain signaling, or inflammation in the brain. But another prominent theory is that heat causes sleep disturbances, which in turn can worsen mental health symptoms.

Warm nights significantly worsen sleep, said Dr. Obradovich. “And we know from a large body of literature in psychology and psychiatry that inadequate sleep, sleep disorders, and insomnia are very closely associated with worsening mental health status over time.”

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


We must not forget the climate scare either, said Dr. Paul. Wildfires and heat waves, among other weather-related events, are increasing in frequency and intensity due to climate change. As global warming worsens, environmental fears could exacerbate other stress, anxiety, depression, or even disaster-related symptoms of post-traumatic stress disorder, he added.

Certain people are also more prone to heat than others. In their 2018 study, the team led by Dr. Obradovich and Paulus found that lower-income people had worse mental health effects from heat than higher-income people, and that women had worse effects than men. Together, they found that the mental health effects of heat were twice as bad in low-income women than in high-income men.

In times of a heat wave, it is not always clear how to protect yourself. But managing your heat exposure, staying hydrated, and avoiding the heat if you can are always good options. Finding people in your community is also a powerful, overlooked strategy, said Dr. Nori Sarma.

This means “neighbors who stop by to see neighbors, friends and family and make sure everyone is okay”.

This article originally appeared in The New York Times.

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