Rising temperatures linked to increased risk of depression, study finds

New research from South Korea has found that for every 1°C increase in average annual atmospheric temperature (from the average temperature in the 1961–1990 period, due to climate change), the odds of having at least moderate depressive symptoms increased by 13%. These increases were 14% for adults between 19 and 40 years of age and 15% for participants who had lived in the same metropolitan area for 20 years or more. The paper was published in the Journal of Affective Disorders.

Climate change is an ongoing global phenomenon characterized by rising temperatures, shifting weather patterns, and more frequent extreme weather events. Many believe that human activities, particularly the burning of fossil fuels and deforestation—leading to increased greenhouse gas emissions—are the primary drivers of this change. These emissions trap heat in the Earth’s atmosphere, causing global warming and disruptions in natural systems.

Estimates indicate that the mean global atmospheric temperature in 2023 was 1.45°C above preindustrial levels. These temperature increases lead to more frequent exposure to high heat conditions, which can have adverse consequences for both physical and mental health. For example, short-term exposure to high temperatures or heat waves leads to heat stress. However, much less is known about how heat waves impact mental health.

Study author Horim A. Hwang and his colleagues sought to examine the association between the increase in yearly average temperatures and the prevalence of depression among people living in South Korea. They analyzed data from the Korea Community Health Survey, an annual nationwide survey that collects data from Koreans aged 19 years or older. Data collection starts on July 1 each year and includes participants from all districts of the country.

The data used in this analysis came from 219,187 individuals living on the mainland of the Korean Peninsula (islands were excluded). The study authors divided participants into rural and urban groups and determined whether they had at least moderate depressive symptoms (a score of 10 or higher on the PHQ-9 assessment). They used Google Earth Engine (GEE) ERA5-Land Daily Aggregated data and data from the Korea Meteorological Administration’s database to calculate how much the temperature of each district in Korea had changed from the 1961–1990 average.

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Results showed that in urban districts, the average annual temperature in 2021 was 1.2°C higher than the 1961–1990 average (12.4°C now vs. 11.2°C in the reference period). There was no difference in rural districts—the average annual air temperature in these areas was 11.9°C in the reference period and remained 11.9°C in 2021.

However, these numbers were not the same across all districts. In some districts, changes in temperature were higher, while in others, they were lower. Overall, in districts where the average annual temperature was higher, the odds of having moderate or more severe depressive symptoms were slightly lower (6% lower for each 1°C increase) than in districts with a lower average annual temperature.

However, the greater the temperature increase in a district since the reference period (1961–1990), the higher the odds that individuals living there would have at least moderate depressive symptoms (13% higher for every 1°C increase). These increased odds were 14% for adults between 19 and 40 years of age and 15% for participants who had lived in the same metropolitan area for 20 years or more. The association was particularly pronounced in urban districts, where the increase in odds was 22% for every 1°C rise.

“This study demonstrated that increases in average temperature difference are associated with increased likelihood of moderate depressive symptoms among adults 40 years old or younger living in urban districts. This study also showed that the increase in average temperature difference is associated with increased likelihood of depressive mood among all adults regardless of age group,” the study authors concluded.

The study brings to light an interesting correlation between weather conditions and depression. However, it should be noted that the design of this study does not allow for causal inferences to be drawn from the results. While it is possible that weather conditions might affect mental health, the reported increase in average temperatures was slight and observed only in urban districts. It is likely that other factors contribute to both the increase in depressive symptoms and the change in temperature in urban areas.

The paper “Association between increase in temperature due to climate change and depressive symptoms in Korea” was authored by Horim A. Hwang, Ayoung Kim, Whanhee Lee, Hyeon Woo Yim, and Sanghyuk Bae.