How extreme heat can impact your mental health as high temperatures sweep US

Dangerously high temperatures have been sweeping across the southern, central and eastern U.S., leaving more than one-third of the country under heat alerts as of Tuesday afternoon.

Actual temperatures are expected to hit triple digits on Tuesday in several cities and states including Philadelphia, Washington, D.C., Virginia and North Carolina while the heat index -- what the temperature feels like -- is expected to hit 104 in Dallas, 108 in Washington and 109 in Little Rock, Arkansas.

The effects of extreme heat on physical health have been well-documented with people at risk of heat-related illnesses including heat exhaustion and heat stroke. Experts, however, tell ABC News that heat can also have a serious impact on mental health.

"In the past, people have talked about seasonal affective disorder and mood changes, which is usually in the winter months … [but] the lack of sun and excessive sun both have mental health challenges and changes," Dr. Asim Shah, a professor and executive vice chair of psychiatry and behavioral sciences at Baylor College of Medicine in Houston, told ABC News.

Shah said excessive sun and heat can alter levels of serotonin -- a neurotransmitter that helps regulate mood, behavior and sleep -- as evidenced in past research. This may lead to changes in mood such as anger, frustration or irritability.

Dr. Nathan Carroll, chief psychiatry resident at Jersey Shore University Medical Center, in Neptune Township, New Jersey, told ABC News that mood changes, including irritability, may come from the fact that extreme heat can raise levels of cortisol, known as the "stress hormone," in the brain.

This increased stress can in turn "make people irritable in the right circumstances," he said.

High temperatures can also negatively impact the quality and quantity of sleep, which can raise levels of cortisol in the body.

Studies have also shown that extreme heat can exacerbate conditions such as depression, anxiety and suicide ideation. For the latter, a 2023 meta-analysis found that even a slight bump in the average monthly temperature can lead to increases in suicide and suicidal behavior.

Additionally, medications people are taking for certain mental health disorders can be worsened by extreme heat. One example is lithium, a mood-stabilizer used to treat bipolar disorder.

Carroll said that lithium can cause the kidneys to release more water, leading to increased urination and sweating, which can cause dehydration. This can also cause lithium levels in the body to become concentrated, which can be toxic.

He added that certain antidepressants, antipsychotics and benzodiazepines can decrease thirst sensations, so people aren't aware they're becoming dehydrated.

Both experts told ABC News that regardless of side effects, people taking medications should not stop doing so before speaking with a doctor.

"It does not mean that you cannot go out in [the] sun, it does not mean that you have to stop taking the medication," Shah said. "It just means that you need to talk to your doctor [about] what precautions you need to take. Do you need to increase the dose or decrease the dosing? Do you need to avoid certain things? Just discuss with your doctor."

These negative impacts may lead to increased hospital visits and admissions related to mental illness.

A 2022 study from researchers in Massachusetts and Minnesota found that days with higher-than-normal temperatures during the summer in the U.S. were linked to increased rates of visits to emergency departments for any mental health-related condition, including mood disorders.

Carroll said there are many reasons why hospital visits increase during extreme heat including the heat exacerbating mental health conditions and people taking medications for mental health conditions, which may dehydrate them and lead them to seek medical treatment.

"The third reason is the hospital is where many individuals who don't have other resources go to get help," he said. "So, if they're trying to get out of the heat, if they're part of the unhoused population, if they don't have anywhere else to turn to, the hospital is a safe place, so they come into here also."

Certain groups are especially vulnerable to the impacts of extreme heat including elderly adults, children and those with preexisting conditions, according to the American Psychiatric Association. However, anyone can be vulnerable to extreme heat.

To manage heat, experts said they recommend people stay in a cool environment as much as possible during high temperatures, drink water to stay hydrated and use stress-management techniques such as meditation to decrease stress levels.