Over the past several years, increasingly destructive hurricanes, wildfires, blizzards, and other extreme weather events have made it clear that the effects of climate change aren’t some future hypothetical, but our current reality. Not to be outdone, the summer of 2023 has been coming in hot — literally — with July shattering the record for the planet’s hottest month, and coming to a close with “numerous fires” breaking out in the Arctic circle. And while the recent high temperatures and debilitating humidity may not be responsible for as much property damage as a hurricane, it’s been disastrous for our mental health.

“Heat waves are becoming more frequent, widespread, intense, and severe, and they’re lasting for longer periods of time,” says Amruta Nori-Sarma, PhD, an assistant professor in the environmental health department at the Boston University School of Public Health. “We call it ‘broken record, record breaking heat,’ and as it continues, more and more people are becoming cognizant of the both physical and mental health impacts of extreme heat exposure.”

Though most people are familiar with the physical effects of extreme heat — ranging from discomfort, to respiratory issues, to heat stroke resulting in permanent disability, or even death — the link between excessively hot weather and mental health isn’t as widely understood. 

But, thanks to a growing body of research, as well as insights from therapists and other clinicians, we now have a better grasp on how oppressive, inescapable heat can wreak havoc on our individual and collective mental health. Rolling Stone spoke with three experts to find out more about this relationship, why it’s a public health issue, and where we go from here.

IT’S NOT UNUSUAL to feel especially cranky and miserable on a sweltering day, but Asim Shah, MD, professor and executive vice chair of psychiatry and behavioral sciences at Baylor College of Medicine, says that’s only the beginning. “When exposed to too much heat, people can get more irritable, angry, aggressive, fatigued, or all of these things combined,” he tells Rolling Stone.

For some people, extreme heat affects more than their mood. 

“Some of my clients have described [experiencing] symptoms similar to seasonal affective disorder, in that they occur always during the hottest parts of summer, and can include increased feelings of depression and isolation, and a lack of motivation, energy, and interest in activities they otherwise enjoy,” says Adam L. Fried, PhD, a clinical psychologist practicing in Phoenix, and the director of the behavioral sciences program at Midwestern University’s Glendale, Arizona campus.

After analyzing data from approximately 3.5 million trips to emergency rooms across the U.S. between 2010 and 2019, Nori-Sarma and other researchers from the Boston University School of Public Health found that the rate of ER visits was eight percent higher on very hot days, compared to the coolest days of the summer. The results of their original investigation were published in an article in JAMA Psychiatry in 2022.

“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,” Nori-Sarma tells 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.” 

Roughly 2.2 million individuals made the 3.5 million ER trips included in Nori-Sarma’s study; however, those data didn’t differentiate between whether or not a patient had a pre-existing mental health condition. The findings were relatively consistent across age groups and gender, although people living in the Northeast, Midwest, and Northwest were slightly more likely to make mental-health-related trips to the ER during heat waves. “This speaks to the adaptive measures that people in the southern parts of the U.S. have already taken to keep themselves safe in hot weather, including a higher penetration of air conditioning usage,” Nori-Sarma explains.

Similarly, a 2021 review of previous studies found that during heat waves, for every 1°C increase in temperature, there was a 0.9 percent increase in hospital admissions and emergency room visits for mental health conditions, as well as a 2.2 percent increase in mental health-related deaths. 

Another review of existing research, published in The Lancet Planetary Health in July, also found that excessive heat has been associated with poor community health and well-being, as well as an increase in attempted and completed suicides. “If you look at CDC data regarding suicide, you will see that suicide rates in May, June, July, August, even September are more than in the colder months,” Shah tells Rolling Stone

Because much of this information comes from hospital visits, the actual numbers are likely higher, given that many people experiencing heat-related mental distress wouldn’t seek treatment in an ER. This could include unhoused or housing-insecure individuals, people with lower incomes and/or are unable to access commercial health insurance, and those with substance use conditions. “People who have some of those other vulnerabilities are likely to be more highly exposed to extreme heat, and probably need more care during a heat wave period,” says Nori-Sarma.

SCIENTISTS HAVE YET TO definitively demonstrate how, exactly, heat causes mental distress.

“The most widely hypothesized explanation is that too much sunlight can make your serotonin levels irregular,” says Shah. “Because serotonin regulates your mood, when you have increased levels of serotonin, you can become irritable [and] feel more anxious and depressed. In extreme situations, you can become disoriented, foggy, or completely confused.” 

There are also studies suggesting that heat may cause inflammation in the brain, which could then contribute to mental health conditions like depression or psychosis, as well as cognitive impairment (like poor memory and concentration).

Another prominent explanation is that high nighttime temperatures can lead to sleep disturbances and deprivation, which have well-established associations with increased irritability, frustration, and negative emotions, as well as most mental health symptoms and conditions. 

“Sleep deficiency or poor sleep quality in general can be big factors in someone’s mental health and mood,” Fried tells Rolling Stone. “In fact, this link goes both ways: sleep problems can be the result of mental health symptoms, but they can also exacerbate them. For example, people with high anxiety and worry may find it hard to fall asleep, or may awaken several times a night with racing thoughts.”

On top of everything else, excessive heat can prevent people from taking part in the activities they rely on to maintain their mental health, or cope with existing depression or anxiety. This is something Fried has encountered practicing in Phoenix — especially during the city’s recent record-breaking streak of 31 days with temperatures of at least 110° F. 

“My clients often report that the prolonged extreme temperatures can make it very difficult for them to engage in activities they traditionally use to manage stress and anxiety, like taking walks and being in nature,” he explains. “It can also feel like more of an effort to make plans with someone [and leave] your house, which can increase social isolation, and exacerbate depression and anxiety symptoms.”

AT THIS POINT, MOST people understand that spending too much time in the sun (without sufficient protection) can cause skin cancers, dehydration, heat stroke, and a number of other illnesses. Moving forward, Shah wants people to get in the habit of considering the mental health effects of heat exposure as well: something he hopes will benefit both individual and collective health. “Extreme heat is not going anywhere, so we need to discuss it as a major public health concern,” he says.

Nori-Sarma echoes that sentiment, explaining that ER visits, like the ones analyzed in her study, are “some of the most extreme interactions” people can have in a medical setting, as well as some of the costliest for healthcare systems. “There’s a lot of potential for improving people’s overall mental health earlier, so we can reduce the need to visit the emergency room during a heat wave,” she says, noting that it would also preserve healthcare resources for other emergencies.


Although growing awareness of heat-related effects on mental health is a step in the right direction, Nori-Sarma stresses the importance of addressing the public health implications of this relationship sooner rather than later. “As climate change continues to create more frequent, intense, and longer-lasting heat waves — which can also intersect with other extreme events, like drought, wildfire, or [destructive] storms — it’s going to have compounding effects on our mental health,” she explains.

If you or someone you know is considering suicide, please call or text 988 to reach the Suicide & Crisis Lifeline. You can also reach out to the Crisis Text Line, a free, 24/7 confidential text messaging service that provides support to people in crisis when they text 741741.