More frequent, intense heat waves taking a mental health toll

It’s widely known that heat can take a toll on the body. Exposure to hot temperatures can lead to dehydration, heat exhaustion, and heat stroke. But the mind and body are connected. Extreme heat has consequences for our mental health, as well. And the risks may be increasing.

“There is no health without mental health,” says Neil Puri, M.D., medical director for the Center for Brain Stimulation at the Menninger Clinic in Houston, Texas. “Mental health impacts physical health, and… physical health problems put you at risk for mental problems.”

As a result of climate change, heat waves are becoming more frequent and intense. Millions of people across the United States and Europe are coping with record-breaking temperatures this summer. Research suggests it’s only the beginning. Scientists project longer and hotter heat waves driven by the Earth’s rising temperature. Researchers are still working to uncover the health implications of a warming world, including rising rates of mental health emergencies in hospitals.

A February 2022 study published in JAMA Psychiatry found a nationwide uptick in emergency department (ED) visits for mental health issues, including stress disorders, mood disorders, anxiety disorders, schizophrenia, and self-harm on days of extreme heat.

For the study, a team of researchers from Boston University School of Public Health examined 3.5 million medical claims for ED visits where patients were treated for mental health conditions during warmer months (May to September) from 2010 to 2019. Their findings showed the rate of ED visits on hot days was higher among men than women. They also found an increase in ED visits in the Northwest, Northeast, and Midwest, where prolonged stretches of hot weather occur less frequently than in the Southeastern and Southwestern parts of the country. But the trend was happening to everyone, everywhere.

“What that indicates to us is that heat is a problem for mental health, regardless of where you live, across the board in adults of all ages, in both men and women,” says the study’s lead author, Amruta Nori-Sarma, Ph.D.

The elevated rate of trips to the ED ranged from a 5 percent increase in visits for schizophrenia, 7 percent for anxiety and mood disorders, to 11 percent for child-onset personality disorders. Those numbers may seem small, but “it’s just the tip of the iceberg,” Nori-Sarma says.

“This is potentially happening among hundreds of thousands of people who are experiencing this,” she explains. “You can imagine there might be a whole host of mental health-associated outcomes where a person would have anxiety or stress, but they may not even come [to the ED].”

The study adds to a growing body of evidence that shows a clear connection between extreme heat and mental health.

In an August 2021 meta-analysis, researchers evaluated 53 studies on heat exposure and mental health outcomes published between January 1990 and November 2020. The studies examined the link between extreme heat and mental health-related ED deaths, visits, hospitalizations. The researchers found that when temperatures rise, the quality of people’s mental health drops—increasing the risk of poorer outcomes: For every for 1° Celsius—or 1.8° Fahrenheit—rise in temperature, mental health-related illnesses increased by 0.9 percent and mental health-related deaths increased by 2.2 percent. The causes of death were due to suicide and self-harm, psychosis, dementia, and substance misuse.

Researchers have also linked hotter days with a slight uptick in suicide rates in the United States and Mexico, estimating there may be up to 40,000 more climate-related suicides in these countries by 2050. Another recent study showed evidence that temperatures above 70° Fahrenheit are associated with more negative emotions, such as anger, as well as more stress, fatigue, and lethargy.

“People need care for these [mental] health issues the same way that they would need care for physical health issues,” Nori-Sarma points out. “It became really clear that we need to understand all of these different factors that people are facing and how they might be interacting to impact people's mental health.”

How extreme heat worsens mental health

Any type of external stressor in our environment can make our mental health worse, explains Dr. Puri.

One of the reasons why extreme heat affects our mental health is because hot weather disrupts sleep patterns, experts say.

“If you don’t have a good quality sleep, which we know that extreme temperatures disrupt, you’re just not going to think as well the next day,” Puri explains. “Poor sleep has been shown repeatedly to lead to toward increased likelihood of mood disorders, increased anxiety, and increased psychosis.”

The optimal temperature for a good night’s rest falls between 60 to 67° Fahrenheit. If the temperature in your bedroom is too cold, your body will amp up its cardiovascular system to keep you warm, but it does not dramatically affect the quality of your rest. If your bedroom is too hot, however, the ambient heat will increase your core body temperature and disrupt your rapid eye movement (REM) sleep. This can make it more difficult for you to fall and stay asleep.

The lack of good sleep creates a domino effect: Studies show that poor sleep is associated with impaired cognitive function and performance, such as attention, learning, memory, and reaction. Because sleep plays an important role in regulating emotional brain function, poor sleep can also adversely affect mood and how we emotionally interpret and recall memories. This can stir up a sense of poor emotional, psychological, and social well-being. It can also make underlying mental health symptoms and episodes feel sharper.

Excessive heat may undermine some of the coping strategies people use to ease pangs of sadness, as well as symptoms of anxiety or depression. Extreme temperatures can be a barrier to physical activities that help people manage their feelings, such as gardening, exercising, or taking a walk outside, Puri explains. Researchers have tested this theory: In several studies, this “exercise withdrawal” led to an increase in anxiety and depression and worsening mood changes, especially after two weeks without exercise.

Some people are more vulnerable than others

Although more intense and frequent heat waves driven by climate change pose a health threat for everyone, it is particularly dangerous for people with existing mental health conditions.

Certain medications used to treat mental health conditions can make the discomfort people experience on very hot days even worse. Health experts point out that these medications—such as drugs for depression, anxiety, bipolar disorder, post-traumatic stress disorder, and schizophrenia—can throw off the body’s natural ability to regulate its core temperature. In addition, some of these medications can cause people to sweat more or feel thirstier, while other medications can inhibit sweat production and thirst. Altogether, these side effects of psychiatric medications can lead to potentially fatal heat-related illnesses during hot weather.

Overall, coping with uncomfortable heat and facing an increased risk for heat-related illness, while managing an existing mental health issue, can take a cumulative toll on a person’s well-being.

Other vulnerable populations include older people with impaired cognitive function and difficulty coping with stress, those living in tropical and subtropical climates, and people living in lower income areas with less access to air conditioning and other cooling strategies who may face additional barriers to mental healthcare.

What can people do?

​Climate change is contributing to more frequent, more severe, and more dangerous extreme heat events. The deadly July 2022 heat wave that swept through Europe was 10 times more likely to occur due to human-caused climate change, according to a study conducted by international scientists at the World Weather Attribution. In the U.S., extreme heat has become the greatest weather-related cause of death in the country for the past 30 years, claiming more than 700 lives each year, according to the National Oceanic and Atmospheric Administration. That accounts for more deaths than those caused by hurricanes, tornadoes, flooding, or extreme cold.

National Aeronautics and Space Administration (NASA) experts predict global climate change will only get worse this century and beyond. That means a higher likelihood of stronger hurricanes, longer wildfire seasons, and more intense droughts and heat waves.

“[Climate change] is not a theoretical future threat,” Nori-Sarma cautions. “It's happening now, and you don't have to look that far away. You can see the exposures happening in communities around the world [and] in people's own backyard.”

Climate change is a global crisis that will continue to affect human health. The disruptions in our physical, biological, and ecological systems due to climate change are expected to exacerbate existing health threats and trigger the emergency of new health threats, such as more lung and heart disease, extreme weather-related injuries and premature deaths, food- and water-borne illnesses, and other infectious diseases, according to the U.S. Centers for Disease Control and Prevention (CDC). Mental health is no exception.

One of the best ways people can reduce the stress of these extreme weather events for themselves and others is by relying on community bonds. Getting involved in the community and checking in on neighbors, friends, and family are “really powerful methods that we've seen actually work in conjunction with access to resources and access to care,” Nori-Sarma says.

In addition to leaning on your community, there are resources and activities you can do to support your own mental well-being. Experts recommend the following tips:

• Meet with a therapist—either in person or online—to talk through issues
• Download apps that teach or promote strategies known to support well-being, including mindfulness, meditation, sleep, and drinking less alcohol
• Get active and social with others in an air-conditioned space to boost endorphins
• Pay attention to your medications and related side effects to recognize if they impair your body’s ability to cope with heat

It’s important to remember that people who are experiencing suicidal thoughts, substance use, mental health crisis, or emotional distress can call the 988 Suicide and Crisis Lifeline. Help is available 24 hours a day, 7 days a week.