The heat index is soaring: Are you feeling more depressed?

Day after day of unbearable heat, Jan Cox feels herself sinking more into a depression.

“There does not seem to be any relief,” said Cox, who has given up gardening and outside activity as the heat index climbs to new records in the Sunshine State.

The 79-year-old Central Florida resident says she has lived in the state all her life, but the unrelenting heat this summer has affected her mental health. “I try not to dwell on it, but the feeling is there,” she said.

While health officials issue warnings for physical danger from extreme heat, like heat stroke and heat exhaustion, just as concerning are the links between high temperatures and mental health issues.

Research shows the high temperatures combined with the thick humidity plaguing the state can take a toll on everything from Floridians’ day-to-day moods to the potential for a mental health crisis, or self-harm.

“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.”

The correlation between heat and mental health is only beginning to be measured as scientists consider whether Americans have the coping mechanisms to handle heat waves as climate change worsens.

Emergency department doctors like Dr. Brian Drummond in Tucson are seeing patients arrive with manic behavior, rage and severe depression just as much as with heat stroke this summer. “It’s the heat and all the other stressors,” he said.

A study of more than 2.2 million people who visited U.S. emergency departments during a 10-year period through 2019 found 8% more visits for men and women for mental health concerns on the hottest days of summer, according to research published in JAMA Psychiatry in February. Earlier research has shown schizophrenia can make people more vulnerable to heat and lead to hospitalizations. And some psychiatric medications can raise body temperature, which can have dangerous effects when coupled with extreme heat.

In Davie, Dr. Johannes Vieweg, dean of the Kiran C. Patel College of Allopathic Medicine at Nova Southeastern University, sees how the daily record high temperatures are affecting students, teachers, drivers and people who work or spend time outdoors. “The chronic heat creates multiple effects on the body,” he said. “Whether hormonal or chemical, the stress can manifest through depression.”

Researchers are studying both brain function and behaviors as mental health triggers. Are people more isolated when it’s hot outside? Do they exercise less and eat less healthy foods? Or is there something physically taking place in the brain that worsens mental health symptoms?

Poor quality sleep may be one of the key links between extreme heat days and mental health declines, experts say.

“There is a close relationship between sleep and temperature,” said Jamie Tartar, a research director with NSU’s Department of Psychology and Neuroscience.  “Extreme temperatures can interrupt sleep quality, and anything that disrupts our sleep can disrupt our mood. At night we want to keep the bedroom dark and cool.”

Genetics may also play a role in someone’s ability to tolerate the adverse effects of high temperatures.

Thomas E. Bernard,  a professor of public health at the University of South Florida in Tampa, believes some people are naturally better able to withstand high temperatures. However, he believes there are actions you can take to build tolerance, such as improve your cardiovascular capacity and stay well-hydrated.

Recognizing your mental and physical limits is critical in Florida this summer, he said.

“If you don’t tolerate heat well, don’t ignore the signs and push ahead,” he said. “If you do that, you are going to be in trouble.”

Sun Sentinel health reporter Cindy Goodman can be reached at cgoodman@sunsentinel.com.