Heat Wave

As the planet warms, study reveals just how much humans will pay to avoid hot weather

New research underscores the true cost of heat waves on our well-being, and our wallets.

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High temperatures can cause high tempers, too. Now, new research shows exactly how much damage hot weather may do to a person's mental health — and how much we are willing to pay to avoid it.

In the new study, researchers find a link between high temperatures and individuals' self-reported mental health. The data comes from 3 million Americans' mental health reports, collected over 17 years. The researchers then compared these with daily weather data from the same time period.

Study participants were asked to report their mental health over the preceding 30 days. Assuming a baseline, "average" temperature of 60 - 70 degrees Fahrenheit, researchers found that when the temperatures dropped below baseline, people tended to report better mental health than when temperatures were hotter.

The researchers also looked at how far people were willing to go to avoid mental distress associated with too hot weather. Across the study participants, Americans were willing to pay $2.60 to $4.60 per day to avoid hot weather, the study found.

The results were published Wednesday in the journal PLOS ONE.

Can't stand the heat

Interestingly, while cooler days had an immediate effect on people’s mental wellbeing, the researchers observed a lag when it came to the toll of higher temperatures. The mental effects of hot days became more obvious as the heat went on, especially after 10 days. The longer heat waves lasted, the stronger their negative effect on mental health, the results suggest.

Conversely, sustained cooler temperatures did not build up good mental health.

Chart showing the number of people who had more or fewer than 14 days of distressed, based on temperature.Li et al, 2020

One reason for this effect, the researchers suggest, may be sleep quality. Hotter days mean losing sleep, which can add to feelings of distress, the authors say. That theory fits with previous research suggesting a link between poor sleep and mental-health conditions like depression.

Managing mental health

In addition to hot weather's toll on mental health, the medications some people take in order to manage mental-health conditions like depression can also cause problems in warmer weather.

Certain mental-health medications, including Beta-blockers, which are used to treat anxiety, can inhibit the body’s ability to sweat, hampering our primary, natural cooling system.

Other medications can cause people’s thirst to change, and many common prescription and over-the-counter drugs can cause dehydration.

If you take more than one drug to manage your health at any one time, that can also magnify the effects of heat on the body's physiological well-being. And as heat waves become more common as the planet warms, these dangers could become increasingly apparent.

Ultimately, the results, while not proving a cause-and-effect relationship between mental health and temperature, do suggest that tracking temperature data and reported mental health may help shed light on the real costs of global warming to our health.

Abstract: This study estimates the association between temperature and self-reported mental health. We match individual-level mental health data for over three million Americans between 1993 and 2010 to historical daily weather information. We exploit the random fluctuations in temperature over time within counties to identify its effect on a 30-day measure of self-reported mental health. Compared to the temperature range of 60–70˚F, cooler days in the past month reduce the probability of reporting days of bad mental health while hotter days increase this probability. We also find a salience effect: cooler days have an immediate effect, whereas hotter days tend to matter most after about 10 days. Using our estimates, we calculate the willingness to pay to avoid an additional hot day in terms of its impact on self-reported mental health.
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