Hot, sticky Louisiana nights when temperatures stay above 70 degrees have a measurable effect on residents’ mental health, according to a study that adds to a growing body of research on the links between heat and psychological well-being.
Researchers analyzing nearly 12,000 calls to Louisiana’s 988 suicide hotline found that calls about suicide increased 19% after nights in the 90th percentile for heat, 55% after nights in the 95th percentile and 166% after the most extreme hot nights, according to the peer-reviewed study, published earlier this year in PLOS Mental Health.
The researchers defined “extreme” heat relative to what is typical for each parish, using percentiles rather than a fixed temperature. A “hot night” in the study generally meant overnight low temperatures in the low to mid-70s in Baton Rouge, New Orleans and Lafayette and the mid- to upper-60s in Shreveport, which reflect the 90th percentile of what is typical for each area.
The findings represent some of the latest research linking heat to mental health crises. Studies across the United States and internationally have found connections between higher temperatures and suicide deaths, emergency department visits for suicidal behavior, violent crime and domestic violence.
Researchers say Louisiana, with its humid subtropical climate and rising nighttime temperatures, offers an example of how heat can strain both the body and the mind.
“This is consistent with what we’re seeing in the broader literature,” said Mostafijur Rahman, an environmental health researcher at Tulane who has studied the relationship between temperature and mental health and was not involved in the Louisiana analysis. “The strongest effects are often tied to nighttime temperature.”
Hot nights
The Louisiana study examined 11,684 crisis hotline risk assessments conducted between 2019 and 2023 by VIA LINK, the nonprofit that operates the 988 Suicide & Crisis Lifeline in the state. Researchers looked at whether suicide-related calls increased on the day of and up to two days after extreme temperatures.
The strongest association was at night, rather than scorching temperatures during the day.
“When it stays hot overnight, you don’t get a break,” said Sophia Ryan, the study’s lead author and a geographer at UNC Chapel Hill who studies climate and mental health. “Your body doesn’t have a chance to cool down.”
Callers didn’t necessarily mention heat as a stressor, Ryan said. But they did talk about difficulty sleeping and having fewer future plans.
Researchers saw that kids were calling at an even higher rate than adults. During heat waves, typical social outlets like sports practice may be cancelled or interrupted, leading to more feelings of isolation, said Ryan.
Heat as a warning
The findings come as Louisiana continues to grapple with intensifying heat. While daytime highs have not increased dramatically in recent decades, minimum temperatures — nighttime heat — have risen steadily since 2000, according to the study.
As Louisiana looks to another sweltering summer, the research suggests that heat waves could serve as a warning signal.
“These are predictable increases in demand,” Ryan said. “If we know we’re going to have a week of really hot nights, that may be a time to consider additional staffing or outreach.”
Rahman said lawmakers could consider policies to to keep air conditioning running during extreme heat. In northern states, utility companies are prohibited from turning off electric service during colder months. The same policies could be put in place in Louisiana for warmer periods, he said.