Extreme Heat Takes a Toll on Our Mental Health

This blog post was written by my colleague Lauren Reiser. 

With major U.S. cities still reeling from the devastation left by Hurricanes Harvey, Irma, and Maria, the threat of climate change to our health and safety is clearer than ever. In addition to the physical dangers posed by severe storms and flooding, natural disasters like hurricanes are traumatic and exact a toll upon our mental and emotional health. The loss of life and livelihoods from severe storms is a significant stressor and has been shown to reduce emotional well-being and impair mental health. However, there is another potential link between climate change and our mental health that doesn’t get as much attention as major storms: extreme heat. Heat has important implications for our mental health, potentially leading to increased emergency room visits, higher risk of death, and reduced emotional well-being.

Extreme heat often is discussed in terms of its impact on our physical health, for good reason. Every year, extreme heat and humidity kills an average of 1,300 people in the United States, a figure projected to increase significantly in the coming decades as our world heats up.

People coping with mental illness can be particularly sensitive to the physical effects of heat exposure, such as heat exhaustion and heat stroke. Those who use certain medications like anti-depressants are particularly vulnerable to the effects of extreme heat. A study published in the journal European Psychiatry found that these medications impacted the body’s ability to regulate temperature, leading to an increased risk of heat-related death for people who have been diagnosed with mental illnesses.

But extreme heat doesn’t just worsen the physical health of people with mental health diagnoses, it can also exacerbate their existing mental health conditions. A study in Toronto found that temperatures above 82 degrees Fahrenheit (28 degrees Celsius) were associated with increased rates of emergency room visits for mental health-related conditions, such as schizophrenia and mood disorders. Researchers in Quebec had a similar finding when they analyzed emergency department visits for “mental and psychosocial problems.” As mean temperature increased, the number of these kinds of visits likewise increased. A recent state-wide study in California further reinforced this link. Researchers surveyed daily counts of mental-health related emergency room visits and found that more of these visits occurred during warmer days.

Why might warmer weather impact mental health in this way? In addition to the physical effects of certain medications on thermoregulation, the California researchers hypothesized that higher temperatures add to the existing stresses of daily life. This can increase the likelihood of risky behaviors, resulting in the increased rates of emergency room visits. Further, certain mental health conditions, like dementia, could impact a person’s ability to avoid heat exposure by taking precautions like staying inside and wearing appropriate attire.

Extreme heat can actually make anyone feel worse—not just people with pre-existing mental health conditions. One study found that temperatures above 70 degrees Fahrenheit (21 degrees Celsius), decreased reports of positive emotions like joy or happiness, and increased reports of negative ones like stress or anger, when compared to average daily temperatures of 50 to 60 degrees Fahrenheit (10 to 16 degrees Celsius). Similarly, another study in Australia focusing on heat and humidity found that increases in humidity were associated with “high or very high distress.” And according to one recent study, heat is even impacting our sleep. The researchers found that increased nighttime temperature was associated with increased occurrences of self-reported insufficient sleep.

Heat waves—which are already a health threat—are projected to become more frequent and intense as the climate warms. A recent NRDC report examining more than 50 major American cities found that coming decades will bring an increase in the number of dangerously hot summer days, particularly if we do not take adequate action to address the threat of climate change. Right now, the Trump administration is deciding exactly how they intend to “repeal and replace” the Clean Power Plan, the country’s first-ever limits on carbon pollution from power plants. These historic climate protections are under attack, in addition to the numerous critical public health standards the administration has already rolled back, delayed, and weakened. Considering the risks that extreme heat poses to both our physical and our emotional well-being, the need to take action on climate is even more crucial for our health, and our happiness.