As global temperatures continue to rise, heat waves pose a growing threat to human mental health and emotional well-being. Recent reviews published in magazines american psychologist suggest that rising temperatures can worsen pre-existing psychiatric conditions, increase aggressive behavior, and impair basic cognitive functions. The findings suggest that climate change poses widespread risks to the nervous system, even affecting people who did not previously have the psychological condition.
Extreme heat is already recognized as a leading cause of weather-related deaths, usually due to physical emergencies such as heat stroke and cardiovascular failure. Conversations about climate change regularly focus on these physical health risks and damage to the environment. Threats to psychological health tend to receive little attention from both the public and medical professionals.
To address this gap in the literature, one researcher sought to create a comprehensive overview of how heat exposure changes the way people think and feel. Previous studies have scattered their focus on individual mental health outcomes, making it difficult to see the big picture. The authors aimed to synthesize this information to reveal exactly how heat causes changes in the nervous system.
“I’ve always been interested in integrative medicine, which bridges physical health and mental health,” says Joseph Taliercio, a clinical psychologist who specializes in integrative behavioral health at NewYork-Presbyterian Brooklyn Methodist Hospital and Weill Cornell Medical College. “As the climate disaster became more apparent, my curiosity naturally expanded to questions about how the environment affects our health.”
This review provides evidence that exposure to extreme heat consistently reduces overall mood and emotional stability. Even in people without a diagnosed mental disorder, positive emotions decrease and fatigue increases when temperatures rise above 21 degrees Celsius (about 70 degrees Fahrenheit). Prolonged exposure to hot weather increases the incidence of depression and anxiety in the general population.
Taliercio noted that such a wide-ranging impact was unexpected. “We were surprised to see how severe the psychiatric effects of extreme heat are, including that even people without pre-existing conditions can feel its effects,” he told Cypost.
Social media activity tends to reflect this widespread decline in sentiment. During the unusually hot days, local social media posts have seen a visible increase in depressing language. Because negative moods can spread through social networks, the review notes that heat can indirectly make you feel depressed even when you’re not outside.
The risks are even more severe for people with pre-existing mental health conditions. Rising temperatures and humidity are closely associated with increased hospitalizations for bipolar patients. Extreme heat and bright sunlight can disrupt regular sleep cycles, making these people prone to manic episodes.
People diagnosed with psychotic spectrum disorders face a particularly high risk during heatwaves. This review provides evidence that people with illnesses such as schizophrenia are at significantly higher risk of premature death during heat waves than people with severe physical illness. This vulnerability is often exacerbated by social factors, as these people may experience homelessness or lack access to air conditioning.
Exposure to heat also tends to increase aggressive behavior and violence. As temperatures rise, crime rates, domestic violence, and gun violence are all certain to increase. The authors point out that prolonged exposure to heat depletes the mental resources needed to control aggressive impulses.
This increase in violence also extends to self-harm. Suicide rates and emergency department visits for self-harm spike especially during warmer months. Research suggests a linear relationship here, meaning that rates of self-imposed violence continue to increase as temperatures rise.
Beyond controlling emotions, heat physically impairs basic cognitive functions. People exposed to hot environments experience slower reaction times, increased impulsivity, and worse working memory. Working memory is the brain’s ability to hold and process temporary information, such as remembering it long enough to dial a phone number.
To explain these results, scientists considered several biological mechanisms. Regulating body temperature requires a large amount of physical energy. If a person is already using mental resources to manage a mental illness, the additional physical stress of cooling down can overwhelm a person’s system.
Exposure to heat also changes the production of essential neurotransmitters, the chemical messengers your brain uses to communicate. For example, extreme heat changes serotonin and dopamine levels. Both of these are deeply involved in regulating mood and stress. Abnormalities in these chemicals explain why anxiety and depression spike during the summer.
Additionally, intense heat can interfere with the production of heat shock proteins. These are specific proteins that cells produce to protect them under stressful conditions. When these proteins don’t function properly due to prolonged heat, they can disrupt the hypothalamic-pituitary-adrenal axis, a key hormonal system that controls how the body responds to stress.
Physical effects such as dehydration and lack of sleep also play a big role. Dehydration slows blood flow, impairs brain enzyme function, and causes confusion and fatigue. Sleep deprivation on hot nights increases inflammation in the brain, further lowering a person’s emotional and mental defenses.
Socially, this review emphasizes routine activity theory to explain summer crime increases. The theory proposes that a warming climate will only push more people outdoors and into public spaces. When more people interact in public spaces, the chances of conflict statistically increasing.
Cognitively, the authors point to the temperature aggression hypothesis. This concept suggests that heat causes people to perceive neutral behavior as hostile. Heat taxes the brain, causing people to lose critical thinking skills and react aggressively when interacting with others.
The review also looked at the compounding factors that make certain people more vulnerable to heat. Older adults are at the highest risk of hospitalization and death because their aging bodies become less efficient at managing blood pressure and hydration.
Geography and urban planning greatly influence heat exposure. Cities often experience heat islands, where concrete and asphalt absorb heat, making urban centers much hotter than surrounding rural areas. Areas with few trees and dense buildings trap heat, putting residents in those areas at a serious disadvantage.
Historically marginalized communities suffer the most from these urban planning issues. The study provides evidence that areas once subject to redlining are now significantly hotter. Redlining is a discriminatory practice in which banks refuse to lend to certain, often minority-populated areas, leading to underinvestment in green spaces and cooling infrastructure.
Finally, psychiatric drug use is a major risk factor during heat waves. Many common medications used to treat anxiety, depression, and psychosis interfere with the body’s ability to sweat and regulate blood flow. People taking these prescriptions are significantly more likely to be hospitalized for a heat-related emergency.
A common assumption is that certain geographic regions are safe from these climate changes. Taliercio warns against this false sense of security.
“Some regions were previously thought to be ‘climate havens’ – areas where the effects of rising temperatures would be limited,” he said. “We now know that these shelters were driven by naive hope. Even within the last year, we are seeing temperatures rise significantly in these regions.”
Studying the precise impact of extreme weather events on mental health presents a number of challenges. The delayed effects of heat exposure mean people may not experience a mental health crisis until several days after the heat wave has passed. This delay makes it difficult for medical professionals to accurately link psychiatric emergencies to environmental temperature.
Additionally, cognitive impairment can be difficult to measure consistently across different populations. Scientists often use different test methods to measure traits such as memory and reaction time, making it difficult to compare data from different studies. It is also difficult to determine whether cognitive decline is caused directly by high temperatures or indirectly by heat-related dehydration.
Future research should establish more consistent testing methods to better track changes in mental health across different climates. The authors also suggest investigating how much patients actually know about the fever risks associated with psychiatric medications. Identifying this knowledge gap could help physicians better educate patients on how to stay safe during extreme summer weather.
In the future, the authors plan to expand this research area. “I continue to be interested in ecological psychology and actively seek to build insights into various aspects of climate change, such as the effects of pollution and the role of green spaces,” Taliercio said.
Overall, the reality of climate change requires a widespread shift in public consciousness. “Climate change represents a health crisis, one from which none of us is immune,” Taliesio added.
Despite the harsh reality of rising temperatures, there is room for optimism. “Despite the existential threat posed by climate change, we need to recognize that promising ongoing efforts exist and that we can make significant progress to protect ourselves and our future,” he concluded.
The paper, “Heat to the Brain: The Effects of Elevated Temperatures on Mental Function, Potential Causes, and Associated Composite Factors,” was authored by Joseph R. Taliesio.
