“It’s been proven that protracted hot weather can make people depressed,” said Dr. Charles Raison, who has done research on heat intolerance and summer-related depression. “It seems as if the system that modulates body temp also modulates mood.”
Raison, professor of psychiatry at the University of Wisconsin-Madison School of Medicine and Public Health, said people with mental illness often have trouble with thermal regulation. “From our data, we know that people with depression tend to run body temperatures higher than average, and they don’t sweat as much. So being depressed could set you up to not be able to tolerate heat well.”