Climate Corner: Heat-Related Risks for Mental Health

The start of summer presents a timely opportunity to learn how rising temperatures impact mental health. Heat waves, defined as two or more successive days of abnormally hot weather, have always been a public health concern, but climate change is magnifying that risk. 2023 was the warmest year on Earth since official record-keeping began in 1850. Maryland, along with most of the United States, is anticipated to have higher than usual temperatures this summer as well. Recent research estimates that 37% of all heat-related deaths can be attributable to climate change. The Paris Agreement set an international goal of limiting global warming to less than 2 degrees C—ideally less than 1.5 degrees C—in order to minimize rising temperature and extreme weather events and to prevent triggering climate tipping points. Unfortunately, we are well on our way to overshooting the 1.5 degree C marker.

Besides climate change, a second anthropogenic factor in heat-related health impacts is urbanization. Cities with lots of pavement and little shading or greenery can be up to 10 degrees Fahrenheit hotter than surrounding areas; these so-called urban heat islands also tend to disproportionately affect low-income communities and communities of color, further exacerbating health inequities. This findings are replicable locally, nationally, and internationally. One study in The Lancet found that increasing a European city’s tree coverage from 15% to 30% could lower temperatures by 0.4 degrees C and prevent a third of premature deaths.

As mental health professionals, it is imperative that we are understand why our patients are at increased risk of heat-related morbidity and mortality. 

Heat stroke is one form of heat-related illness, defined as elevated core body temperature (typically greater than 105 degrees F) and neurological changes in the setting of an environmental heat load. The classic form (also called passive heat stroke) occurs in individuals whose bodies cannot effectively dissipate heat from the ambient environment. Populations particularly at risk include older adults and young children, as well as people who are socially isolated or immobile. Many psychiatric medications affect the body’s temperature regulation and/or cooling mechanisms, thus conferring risk for classic heat stroke: beta-blockers, anticholinergics, SSRIs/SNRIs, TCAs, MAO-Is, antipsychotics and sympathomimetics. Exertional heat stroke occurs in the context of outdoor physical activity, with at-risk populations including outdoor workers, soldiers, or athletes. Amphetamines and alcohol increase the risk of exertional heat stroke. 

Patients with schizophrenia are at especially high risk of heat-related mortality. One study analyzing mortality during an extreme-heat event in British Columbia in 2021 found that patients with schizophrenia had the highest odds-ratio of all-cause mortality during extreme-heat events (3.07 [2.39, 3.94]), higher than people with kidney disease (1.36 [1.18, 1.56]) or ischemic heart disease (1.18 [1.00, 1.38]); looking at heat-related causes of death specifically, the odds ratio for people with schizophrenia was 3.99 [2.62, 6.08]. The Washington Post ran a poignant article last year about one young man with schizophrenia who died during an Arizona heat wave. An additional consideration for psychiatrists includes counseling patients on lithium. The risk of lithium toxicity is higher in a setting of fluid loss, such as significant sweating induced by hotter temperatures.

Rising temperatures have other serious public mental health impacts too. A 2023 meta-analysis found that a 1 degree C increase in ambient temperatures leads to a 1-2% increased incidence of suicide (specifically, an increase of 1.5% for average monthly temperature based on data from 3 studies and an increase of 1.7% for average daily temperature based on data from 5 studies). That same meta-analysis reported 9.7% higher incidence of hospital presentation or admission for mental illness relative to periods without heat waves. An Australian study found that rates of domestic violence increased with daily ambient temperature, and tended to occur indoors.  Other types of violence also increased. Green spaces in urban areas are also important cooling mechanisms for urban heat islands and are associated with decreased rates of violence.

So, what can you do to address these overarching issues? 

As an individual, to decrease greenhouse gas emissions that cause climate change, you can switch to renewable sources of energy, purchase solar panels, use heat pumps for heating, or reduce your overall electricity use (by switching to energy efficient appliances and lightbulbs, raising the temperature on your thermostat, washing clothes in cold or warm water, or line-drying your clothes). To reduce the effects of urban heat islands, you can make changes to your own home like installing reflective roofs, planting trees and greenery, and switching to energy efficient appliances. Many of these home changes qualify for tax incentives in Maryland. You can also volunteer at tree plantings to help Maryland reach its goal of planting 5 million native trees by 2030 as a climate mitigation effort. 

As a mental health professional, you can discuss heat-related risks with your patients. A helpful toolkit for monitoring and mitigating risk of heat stroke by patient population is available here. Additional educational tools for patients and psychiatrists can be found on the Climate Psychiatry Alliance website. The CDC just released a national heat and health tracker that provides daily temperatures, number of heat-related Emergency visits, and expected length of heat waves in every region of the country.

As a resident and/or citizen, you can call or email your local, state, and federal representatives to express your concern about the health impacts of climate change and extreme heat; you can find all of your legislators here: https://www.usa.gov/elected-officials.

The author thanks Maryland Psychiatric Society (MPS) for their editorial support; portions of this article was first published in the June and July editions of “MPS News.”