When temperatures exceed 40°C, many report feeling more irritable, nervous, exhausted. A new American study suggests that this discomfort is not limited to a few unpleasant days: it could be accompanied by a lasting increase in
depression and theanxiety
in the population.
Published in the Journal of Psychiatric Researchthis research compared exposure to extreme heat and the frequency of anxiety and depressive disorders in the 50 US states. The results echo other international work that already describes heat waves as a risk factor for mental health. And the trend seems set to intensify.
Extreme heat and mental disorders: what the American study shows
The authors counted, for each state, the average number of days above 100°F (about 38°C) between June and September 2020, then linked it to 2022 data on prevalence of
depression andanxiety from the Centers for Disease Control and Prevention. They took into account age, gender, education level, health insurance status and ethnicity. “Climate change is a very real phenomenon that affects many people around the world, particularly mental health in the form of anxiety and depression” said Dale Pendleton of Rush University Medical Center and Aneta Kwak of Ann & Robert H. Lurie Children’s Hospital in Chicago, cited by PsyPost.
Overall, states had 51% of people reporting mental health issues and nearly eight days of extreme heat. The analysis shows that for each additional 10 days of intense heat, the probabilities of reporting anxiety or depressive disorders increased by 6.2%. The states most affected by the heat also had more difficulties among less educated and uninsured populations. “These findings suggest that the mental health impacts of climate-related heat exposure may be significantly worse in states with greater social and structural vulnerability, highlighting the intersection between environmental stresses and inequities in education and access to health insurance.,” the researchers explained.
Psychiatric emergencies, suicides: a signal already visible elsewhere
The American figures match other data. In Canada, the National Institute of Public Health of Quebec observed up to 29% more admissions to emergency rooms for schizophrenia, mood disorders and anxiety disorders during heat waves in Toronto. Studies also report an increase in the risk of suicide of 1 to 37% per degree above a temperature considered comfortable. In Europe, the Climate-ADAPT Observatory describes links between heat waves, worsening mood disorders and increased psychiatric admissions, particularly among people already under psychiatric care.
The American authors point out, however, that other factors play in parallel. Heat acts more as an amplifier in a context that is already harmful to mental health.
A warning about mental health inequalities in the face of climate
The American study did not make it possible to follow people individually or to finely integrate access to care or local heatwave management policies. The researchers nevertheless emphasize that the trends observed are consistent with work on mortality and hospitalizations during heat waves, which more strongly affect people in precarious situations, psychiatric patients, outdoor workers or residents of poorly insulated housing.
“We would like to emphasize that this study highlights the importance of expanding health research related to climate change, as the health consequences of these changes remain underestimated, particularly with regard to mental health. Climate change represents a fundamental threat to human health, with implications not only for individuals, but also for the sustainability and resilience of health systems. By focusing on the association between environmental exposure and social vulnerability, this work highlights the need to expand research to inform public health planning and policy.” conclude the authors.