Researchers at the BU School of Public Health found the mental health impact of extreme heat was similar across age groups, and evident in both men and women. Photo by AntonioGuillem/iStock

Mental Health

Summer Heat Can Drain Mental Health

New study: extremely hot summer days, more common with climate change, increase emergency room visits for mental health crises

We might all dream of warmer days, of fun times at the beach or by the pool. But in reality, scorching summers can often leave us feeling physically drained—or worse, suffering from heat rashes or heat stroke. Now, a new study led by researchers at the Boston University School of Public Health suggests extremely hot days may also take a toll on our mental health.

In a study published in JAMA Psychiatry, they found that the number of patients seeking mental health support at an emergency department (ED) in the United States went up during periods of intense heat. Summer days with higher-than-normal temperatures were particularly associated with increased rates of ED visits for childhood-onset behavioral and substance use disorders, anxiety and stress disorders, and mood disorders.

The nationwide study is the largest and most comprehensive analysis of daily ambient temperature and mental health–related ED visits among US adults of all ages. With days of extreme heat expected to increase due to worsening climate change, the findings fill a critical gap in research and provide evidence-based support for proactive interventions and policy solutions that can reduce heat-related crises.

“Emergency department visits represent some of the costliest interactions within the healthcare system,” says study lead author Amruta Nori-Sarma, a BU School of Public Health assistant professor of environmental health. “Addressing the needs of the most vulnerable to preempt some of these visits can have a positive impact on individual health and costs, as well as preserve healthcare resources for other emergencies.”

Northeast States Among Most Impacted

The researchers analyzed approximately 3.5 million ED visits among 2.2 million adults ages 18 or older who had commercial or Medicare Advantage health insurance during the warm season—May to September—from 2010 to 2019. The medical claims data on mental health–related ED visits came from OptumLabs Data Warehouse, which contains deidentified, longitudinal health information on more than 200 million commercial and Medicare Advantage enrollees throughout the United States.

The mental health impact of extreme heat—defined as temperatures above the 95th percentile of temperature distributions by county—was similar across age groups, and evident in both men and women in every region of the country. “These results show that heat can profoundly impact the mental health of people regardless of age, sex, or where they live,” says Gregory Wellenius, a BU School of Public Health professor of environmental health and senior author on the study.

The impact of heat was slightly higher in the Northeast, Midwest, and Northwest—even though those regions generally have lower temperatures than the Southeast or Southwest United States.

“That is exactly why the populations in these areas might suffer the most during times of high temperatures,” Nori-Sarma says. “They don’t necessarily have the skills or resources in place to cope during times of extreme heat. Heat events will become even more extreme as the climate continues to warm, so it’s doubly important to identify the populations that are most vulnerable and to help them adapt to warmer summertime conditions.”

Preparing for Hot Days

In future studies, the researchers aim to identify public health strategies that will help alert people to the risks posed by extreme heat and better protect the most vulnerable. They also plan to explore the impact of elevated temperatures on mental health during longer periods of time, including prolonged heat waves. In the meantime, Nori-Sarma warns, the continuing effects of COVID-19 on mental health—and the limited availability of mental health services—coupled with extreme heat should prompt healthcare providers to be proactive.

“As we approach the upcoming summer season, it is important to keep in mind that the combination of stressors—pandemic and climate—might exacerbate existing mental health conditions,” says Nori-Sarma. She encourages providers to prepare for an increased need in mental health services when hot days loom—and to proactively reach out “to patients with existing mental health conditions.”

That’s advice that can apply to the rest of us, too, says Wellenius, who also directs SPH’s Program on Climate & Health.

“On days of extreme heat, it is important that we each take the precautions necessary to take care of ourselves and our loved ones,” he says. That can include checking on neighbors or family members who may be susceptible to health impacts of heat exposure.

This research was supported by grants from the National Institutes of Health’s National Institute of Environmental Health Sciences and the Wellcome Trust.