Exposure to extreme heat is associated with a higher prevalence of depression and anxiety disorders at the level of entire U.S. states. This conclusion was reached by researchers who analyzed data from all 50 states. The study was published in the Journal of Psychiatric Research (JPR).

The authors examined how climate extremes may affect population mental health. The research was prompted by the increasing frequency of heat waves, wildfires, and other manifestations of climate change in the United States.

For their analysis, the scientists used data from federal agencies. They calculated the average number of days with temperatures above 38 °C (100.4 °F) in each state during the June–September period of 2020, the peak summer season. These figures were then compared with the prevalence of depression and anxiety in 2022 to account for a possible delayed effect of heat exposure.

The analysis revealed a stable positive association: the more days of extreme heat a state experienced, the higher the rates of depression and anxiety disorders were two years later. According to the authors’ estimates, each additional 10 days with temperatures above 38°C was associated with a 6.2% increase in the likelihood of mental health problems.

This association remained significant even after adjusting for demographic and socioeconomic factors, including age structure, sex, racial and ethnic composition, educational attainment, and the proportion of people without health insurance. The median prevalence of anxiety and depressive symptoms across states was about 51%, while the median number of extremely hot days was around eight, although variation between regions was substantial.

The study also showed that social vulnerability amplifies the impact of heat. States with lower levels of education and a higher proportion of uninsured residents exhibited higher rates of mental health disorders. According to the authors, this points to an intersection between climate risks and social inequality.

An unexpected finding was that states with a larger share of residents aged 65 and older had lower levels of anxiety and depression, contradicting the common assumption that older adults are more vulnerable to climate-related stressors. The authors emphasize that this effect requires further investigation.

The researchers called for expanded studies on the impact of climatic factors on mental health and urged that these risks be taken into account when developing public health and climate adaptation strategies.