“There are very specific behavioral changes that we all feel with extreme heat,” says Robin Cooper, MD, an associate clinical professor in the department of psychiatry and behavioral sciences at the University of California in San Francisco School of Medicine, and the president and cofounder of the Climate Psychiatry Alliance.  Heat can affect anyone’s irritability, memory, attention, and reaction time, as well as sleep, according to the American Psychiatric Association (APA). (And not sleeping well can certainly interfere with mood and mental health.) For people with certain mental health conditions, these effects are exacerbated.  Additionally, certain medications used for psychiatric treatment (such as antidepressants and antipsychotics) can affect the way the body regulates heat, and in some cases the conditions themselves interfere with body temperature regulation, according to APA. And for people with certain psychiatric conditions, these changes can increase the risk of dangerous symptoms or behavior, Dr. Cooper says. An example: “The experience of extreme heat in certain people with psychiatric conditions is actually connected to aggression and violence.”  One recent study, for instance, showed that extreme heat is associated with spikes in online hate speech throughout the country; the paper was published in September 2022 in the Lancet Planetary Health. And heat waves are happening more frequently in major cities around the United States, according to the Environmental Protection Agency (EPA). Scientists reported an average of two heat waves per year in the 1960s compared to an average of six per year during the 2010s and 2020s.  Additionally, the current average heat wave season across 50 U.S. cities is now about 49 days longer than it was in the 1960s.  Because these episodes are becoming more frequent and long-lasting, Cooper says it’s important to understand the specific ways extreme heat has an impact on mental well-being and functioning, especially for people with mental illnesses. 

The Data Behind How Heat Affects Mental Health

Between 2010 and 2019, emergency rooms around the country experienced an uptick in mental health related visits during periods of extreme heat, according to a study published February 23, 2022, in JAMA Psychiatry. “We found that increased summertime temperature was associated with increased rates of emergency department visits for any mental health cause, as well as for specific outcomes, including mood disorders, anxiety and stress disorders, schizophrenia, substance use disorders, and self-harm,” says Amruta Nori-Sarma, PhD, MPH, the lead author of the study and an assistant professor in the department of environmental health at the Boston University School of Public Health in Massachusetts.    Other research suggests that heat waves may even have fatal consequences for people with certain mental health conditions. An older study published in the journal Psychiatric Services found that patients in state psychiatric hospitals in New York City had twice the risk of dying during a heat wave compared with the general population of New York City. The authors theorized that both the illnesses and the use of antipsychotic medications may have contributed to this correlation. It’s significant to note that suicide rates are higher during abnormally hot months. A study published August 2018 in the journal Nature Climate Change found that a rise of 1 degree Celsius (nearly 34 degrees Fahrenheit) in average monthly temperatures increased suicide rates by 0.7 percent in the United States and 2.1 percent in Mexico. The researchers estimated that, without action to address it, climate change might account for as many as 9,000 to 40,000 additional suicides by 2050 in the United States and Mexico.  “That number just wipes out the contributions of every suicide prevention program and all the gun legislation efforts,” says Cooper about the prediction.

Why Does Extreme Heat Worsen Mental Health?

Researchers haven’t identified an exact reason why extreme heat is linked to worsening mental health symptoms, but according to Cooper, several complex factors probably play a role. Here are five.

Heat May Hamper Brain Function

Extreme temperatures could spell trouble for how your brain operates in several ways.  An area of the brain called the hypothalamus, which helps keep the body’s internal temperature in check (and also helps with basic functioning, like hunger, thirst, mood, sex drive, blood pressure, and sleep), may not function normally when people with certain health conditions are exposed to extreme heat, Cooper says. “It’s pretty clear that there is something biologically happening,” she explains. Research also shows extreme heat may hamper working memory and attention. In a paper published July 10, 2018, in the journal PLoS Medicine, college students who studied in rooms without air conditioning during a heat wave performed as much as 13.4 percent worse than their peers on a series of cognitive tests. Heat may also interfere with the brain chemical serotonin, which helps regulate mood and alleviate aggression, according to the World Economic Forum. Though more research is needed to better understand the brain’s response to extreme heat, Cooper says it’s clear that brain chemistry plays a role.

Certain Mental Health Conditions May Predispose You to Heat Issues

“There is some evidence that the mental illness itself may have some adverse impacts on thermoregulation in the body — that’s the body’s ability to stay cool,” says Cooper. For instance, according to a review published in the journal Schizophrenia Research, people with schizophrenia have a harder time adjusting to hotter temperatures than people without this condition. In a more recent study, published in December 2021 in Environmental Science and Pollution Research International, scientists found that exposure to heat was associated with an elevated risk of hospitalization among people with schizophrenia.

Psychiatric Medications Might Alter How Your Body Regulates Heat

The medicines people with mental health conditions take to control their symptoms — such as antidepressants and antipsychotics — may affect how their bodies respond to heat, the APA states. Along with people taking antipsychotics, those who take anticholinergic drugs — which are sometimes prescribed for depression — and anti-anxiety drugs appear to have an increased risk of hospitalization for heat-related illnesses during a heat wave, per a study published the journal European Psychiatry. The authors noted that individuals who take psychiatric medications should talk with their doctors about the risks and benefits of using their medicines during periods of extreme heat.

Hotter Temps Make It Harder to Sleep

When a heat wave strikes, our sleep often suffers. Experts believe this lack of quality sleep could have a ripple effect on people with mental health conditions. It’s well-established in research that insufficient sleep can make symptoms of mood disorders, such as anxiety and depression, worse. “Disturbed sleep and daytime discomfort during extreme heat might be the biological mechanisms that contribute to increased rates of emergency department visits, so these may be important things for patients to monitor,” says Dr. Nori-Sarma.

Dehydration Risk Is Higher During Heat Waves

Everyone is more likely to experience dehydration during periods of extreme heat, the Mayo Clinic states. For people with mental health conditions, dehydration can impair cognitive function and the effectiveness of medications, which in turn may worsen their mental health symptoms, says Cooper.

How to Beat the Heat and Maintain Your Mental Health

It’s important for everyone, but especially someone with a preexisting mental health condition, to take specific steps to stay cool during extreme heat. Proactive steps to avoid overheating will be your number one tool to lower all these risks, Cooper says. She recommends that you talk with your care team, including general practitioners, psychologists, and psychiatrists, about the potential risks of extreme heat and come up with preventive strategies before heat strikes. Here are some simple but effective ways to stay cool, per the Climate Psychiatry Alliance.

Keep rooms cool. Lower the shades to reduce heat, and use a fan. Note that if the temperature in the room is above 90 or 95 degrees, fans will no longer cool the air.Take cool showers. Jump in a cool shower or place a cool cloth on your face, neck, or arms to help counteract hot temperatures.Wear the right clothing. Loose cotton fabrics are best for staying cool. Also, consider donning protective gear like a hat and sunglasses when you’re outdoors in the hot sun.Drink enough water. Be sure to drink water throughout the day — but try to avoid beverages that contain caffeine and alcohol, because they can be dehydrating. On an ordinary day, women should consume about 11.5 cups of water a day, and men should consume about 15.5 cups per day, per the National Academies of Sciences, Engineering, and Medicine (NASEM) — and if you’re planning to be out and about in hot temperatures, you should drink even more than that, NASEM experts advise.Find a cool place when you’re out and about. Locate a cooling center in your community, or visit an air-conditioned mall, library, or bookstore to retreat from the heat. Avoiding extreme heat for just a few hours a day can make a difference, according to Cooper.Take your meds. Always take your medications as prescribed unless your doctor tells you otherwise.Make a plan to get help if you need it. Have a strategy in place in case you experience signs of heat exhaustion. For instance, before a heat wave, you might want to ask a friend or family member to check in on you a couple times a day once outdoor temperatures spike.

Watch out for symptoms of heat exhaustion, which can happen when your body gets too hot. According to the CDC, signs of heat exhaustion include intense sweating, a weak and rapid pulse, nausea or vomiting, and weakness or tiredness. If you’re showing signs of heat exhaustion, move to a shaded or air-conditioned place, drink water, cool yourself off with damp sheets or a fan, or take a cool shower to lower your body temperature, the Mayo Clinic advises.Another serious condition to watch out for, called heatstroke, occurs when your internal body temperature reaches at least 104 degrees Fahrenheit, according to the American Academy of Family Physicians. In addition to a high fever, the CDC states, the signs of heatstroke include skin that’s hot, dry, red, or damp, a fast, strong pulse, headache, dizziness, nausea, or fainting. If you have symptoms of heatstroke, you should seek emergency medical attention immediately. People around you should try to help cool you off, but don’t drink any fluids while you wait for medical help, Mayo Clinic experts warn.