Summer heat is wearing on Korea's mental health, researchers say

Researchers are finding that extreme summer heat can worsen depression and anxiety, set off panic symptoms and coincide with a higher risk of violent crime as Korea's summers grow more severe.

A Seoul National University Graduate School of Public Health survey released in June suggests the strain is not confined to people with a diagnosis. The survey said more than 77 percent of respondents reported experiencing each of 10 types of stress during extreme heat.

A total of 96.4 percent said their mood worsened for no apparent reason and stress built up, 95.7 percent reported lethargy and reduced ability to work and 94.6 percent said tasks felt irritating or bothersome.

Psychiatrists say the load falls hardest on people already living with a psychiatric condition.

Jang Yun-song-i, aged 22, has bipolar disorder and says summer is consistently the hardest season, to the point that ordinary daily life becomes harder than it is at other times of year. Bipolar disorder cycles between manic and depressive episodes. In manic phases, the heat sharpens anger and irritability. In depressive phases, the stifling air drains energy and low moods last longer than usual.

Panic disorder also flares in summer for Jang.

"When it is hot and humid, I sweat and my heart races," Jang said. "Because that feels so much like panic, it becomes hard to breathe and the fear rushes in." Jang carries ice water all summer in case an attack arrives without warning.

Online communities where people share their experience of mental illness carry the same pattern. After one user posted on July 31 that summer left them more depressed and listless, others agreed.

"It is so hot that I stay home, so my body is in bad shape and I get more sensitive," one wrote. "I cannot sleep at night because of the heat, so I am worn out during the day," wrote another.

Clinicians describe a path that runs through both the body and the daily routine.

"When heat cuts down how much people go out and move, the risk of depression and anxiety disorders rises," said Lee Hae-kook, a professor of psychiatry at Uijeongbu St. Mary's Hospital. "When it is hot and humid, the body's response resembles the symptoms of panic, so extreme heat can act as a trigger for it."

A team from the Catholic University of Korea, Seoul National University and Pusan National University put numbers on the effect. Writing in the Journal of Affective Disorders in December 2024, the researchers found that a rise of 1 degree Celsius (1.8 degrees Fahrenheit) above a district's long-term average temperature was associated with a 13 percent higher likelihood of moderate depressive symptoms and a 24 percent higher likelihood of a depressed mood.

The study drew on responses from 219,187 people in the 2021 Korea Community Health Survey. The effect on depressed mood held across every age group.

A Yale University and Korea University team has tied heat to aggression. Reporting in Scientific Reports in February 2024, the researchers analyzed daily crime and weather records from 201 districts across Korea between 2016 and 2020.

They found the risk of violent crime ran 11 percent higher on days when the local mean temperature sat at the 70th percentile of the summer range than on days at the 10th percentile. Assault and domestic violence were each 12 percent higher.

Korea's own crime figures follow the seasons. National Police Agency statistics show 386,051 crimes in the first quarter of last year against 451,278 in the third, about 17 percent more. Violent crime rose from 48,931 to 57,662 over the same quarters, an increase of about 18 percent.

Frontline officers say they feel the difference.

"Callouts seem to run about 40 percent higher in summer than in winter," said a senior inspector at Geumcheon Police Station with 29 years of service. "It is hot and humid, so people react more sharply to the slightest brush against them, and small arguments often escalate into assault."

Some experts now argue that heat should be treated as a social problem, with responses tailored by region, age and income. Average summer temperatures are climbing and the number of punishing days is growing, they say. On that reading, heat has reached the point of threatening individual mental health and public safety.

"Climate stress, the mental harm done by weather such as extreme heat, varies in severity above all by socioeconomic level," Lee said. "If you do not have the means to escape the heat, you are exposed to more of the risk."

Heat policy, on that argument, would have to go beyond issuing weather bulletins to active support for the people most exposed. You Myoung-soon, a professor at the Seoul National University Graduate School of Public Health, made the same case when releasing the perception survey.

"The government and local governments should treat heat waves as a social risk and respond in a way that examines risks at various levels, including the threat to mental health," You said.

BY LEE GYU-RIM [cho.yongjun1@joongang.co.kr]