Illustration for article titled Hotter Days May Leave You More Stressed, Depressed
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The world is warming. That’s no secret. Extreme heat isn’t only dangerous for our physical health, though. New research shows hotter days may hurt our mental health as well.

A study published Wednesday in the journal PLOS One adds to a growing body of literature showing the way the climate crisis could harm individual mental health and cognitive functioning. This study, in particular, looks at how temperature affects how likely people are to self report their mental health using stress, depression, and emotional problems as measures. It also offers a dollar amount on these health impact, a first for this type of research.

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“In a rapidly warming world, temperature increases pose a challenge to achieving the [United Nations Sustainable Development] goal of ‘good health and well-being,” lead author Mengyao Li, who conducted this research as a PhD student at the University of Georgia, told Earther. “Our study is also the first to attempt to quantify the effect of temperature on self-reported mental health in monetary terms.”

In the age of climate change, we’ll all be seeing plenty of hotter days. We just lived through the hottest decade in recorded history. Temperature records seemingly break all the time whether its Russia, Australia, Pakistan, or even the Arctic. Attaching a more firm cost to this could be the push policymakers need to take action on global warming. Unfortunately, money talks.

In short, the study found that cooler days, compared to the 60 to 70 degree Fahrenheit range that is comfortable for most people, saw individuals report fewer days of poor mental health. Days hotter than these temperatures, on the other hand, increased the likelihood they’d report negative mental health. The study authors, all of whom hail from the University of Georgia’s Department of Agricultural and Applied Economics, relied on individual-level mental health data from the Behavioral Risk Factor Surveillance System that the Centers for Disease Control and Prevention maintains. This system uses annual surveys where people answer a question on how many of the last 30 days they experienced “stress, depression, and problems with emotions.”

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The team of economists reached the study’s conclusion after first analyzing county-level data on temperature and precipitation over 30-day periods from 1993 to 2010, the years the health surveys cover. The researchers examined how many days were higher than 60 to 70 degrees Fahrenheit. Then, they looked at how the self-reported mental health data for that period correlated to the hotter days, as well as cooler days where temperatures were colder than 20 degrees Fahrenheit.

The researchers were able to control for some social factors, such as poverty and seasonal weather fluctuations in states. For instance, summers in Minnesota are unlike summers in Georgia. Still, a major limitation to the study is that the data doesn’t allow the team to explore how community-level factors—like a neighborhood’s air quality, amount of green space, and safety level—affect this relationship. Mental health is complicated, and this all plays a part. And while they’ve found a correlation, the study authors aren’t declaring a causal impact between mental health outcomes and heat. 

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For the study’s cost analysis, the study controlled for individual demographic data, including household income, to see how temperature changes may affect the outcome. They also use a long-standing technique pioneered by Nobel Laureate Gary Becker to estimate how much the average American would be willing to pay to mitigate the impact of temperature on poorer mental health. This allowed the researchers to analyze the economic trade-off between household income and warmer days that happens when individuals suffer from this seasonal distress. That’s how they came up with the dollar cost of all this heat to mental health that adds up to nearly $5 per person for every additional warmer day suffered.

“Calculating people’s willingness to pay is a way to help us quantify the monetary effect of temperature on mental health,” Li said.

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Marshall Burke, the deputy director of the Center on Food Security and the Environment at Stanford University, has published research finding that suicide rates will increase with climate change. He wasn’t involved in this recent paper, but he told Earther in an email, “[t]he results line up very nicely with what the recent literature is saying.”

Alexander Trope, a physician with the University of California at San Francisco’s Department of Psychiatry who sits on the steering committee of the Climate Psychiatry Alliance, described the study’s methodology to Earther in an email as “robust.” He wasn’t involved in the study but noted that its release comes at an interesting time as the world deals with the mental health impacts that come with the fears and anxieties that surround the coronavirus and all the ways it’s changed our lives.

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As we approach the summer months, how will the covid-19 pandemic affect the already vulnerable state of individuals’ mental health? If summertime already brings along more stress and depression, what will that look like as individuals face social isolation and increased economic stress? We’ll have to wait and see if researchers tackle these questions next, but we already know that the future doesn’t look too reassuring if the world continues to ignore the climate crisis.

Senior staff writer, Earther. All things environmental justice, please. I'm addicted to Stardew and love few things more than I love my cat.

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