Does the hot weather have you feeling moodier or less productive?
It’s not just you. Decades of science show that higher-than-comfortable temperatures lead to poorer work performance and mental health.
As a heat wave hits the Midwest this week, and global temperatures rise, some scientists say we should consider the wide-ranging implications of higher temps.
Higher temps have been linked to lower motivation, higher suicide rates, higher ER visits for mental health reasons and poorer test scores. Other scientists say it’s still unclear how high temps exacerbate brain diseases.
“It’s very alarming to think of the implications of a higher average temperature,” says José Guillermo Cedeño Laurent, researcher of climate effects on the brain at Rutgers University.
He led a study that showed student cognitive performance declined in dorms without air conditioning during a 2016 heat wave in Boston.
Students randomly assigned to dorms with and without AC were tracked over 12 days when the Boston area had a heat wave. The students performed tests on their phones that measured reaction time. They were tested on simple addition and subtraction, and with a Stroop test, where students were presented with a word of a color printed in a different color. Students had to answer with the color of the word, not the word itself.
Students without AC were in rooms with temps averaging around 80 degrees, compared to 71 degrees in rooms with AC. The warmer students’ cognitive performance was 10% lower than that of the cooler students, the study found.
“It was surprising to see the size of the effect,” Cedeño Laurent says.
For the first time, a study showed that excessive heat affects not just the elderly or very young — who are more prone to be hurt or killed in heat waves — but also affects young adults who are usually considered to be immune to heat, he said.
Studies as far back as 1976 have linked lower work performance with uncomfortably high temperatures.
The ideal indoor working temperature is 72 degrees, studies show. But even though some workers still felt comfortable in air between 75 and 82 degrees, their mental performance declined between 6% and 10%, according to a 2021 study.
It’s unclear how the heat affected mental performance, Cedeño Laurent says. He was able to measure how the heat interrupted sleep — about a half hour of lost sleep on average for the students in the hotter rooms in his dorm study. But it’s unclear if mental performance was affected by the heat, or because of an underlying effect on the brain, he says.
High heat has also been linked to higher suicide rates, according to a 2018 study in the U.S. and Mexico. The authors estimated that unmitigated global warming could result in between 9,000 and 40,000 additional suicides in the two countries by 2050.
Visits to emergency rooms for mental health reasons also rise on days with extreme heat, a 2022 study found.
It’s important to understand how high heat affects emotional health on a community level because global warming is causing more heat waves, says Elena Grossman, who heads University of Illinois Chicago’s Climate and Health Institute.
The mental health effects of heat waves have two components, she says. There’s the event itself, like the stress of having to leave your home for a cooling center, or losing a loved one. Then there’s the potential for post-traumatic stress disorder and anxiety about future heat waves, Grossman says.
Excessive heat has also been linked to a rise in violence. Grossman pointed to a 2020 study that found heat waves in Africa led to violence between herders and farmers.
“Whether it’s heat impacting a person’s decision-making processes or sleep, we know that it’s linked to our physical and mental health,” Grossman says.
Staying hydrated is one of the best ways to combat excessive heat. In his dorm study, Cedeño Laurent found that students who drank six glasses of water a day were able to minimize the performance declines from the excessive heat.
“It was basically protecting people from the bad effect,” he said.
