Climate change takes a chronic psychological toll

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Heat waves, stretches of wet weather, long-term climate warming, and hurricanes all take a toll on mental health, researchers reported yesterday in the Proceedings of the National Academy of Sciences. All of these phenomena are expected to become more frequent and intense with climate change, suggesting a need to bolster our collective psychological as well as physical infrastructure to prepare.

Scientists have been investigating the mental health consequences of climate change for about a decade. So far, most studies have focused on local areas, specific weather events, or the most severe mental health consequences. The new study starts to sketch in a broader picture of how climate change might trigger a slow erosion of overall mental well-being across a whole country.

The researchers analyzed data on mental health difficulties reported by 2 million randomly selected US residents between 2002 and 2012 as part of the US Center for Disease Control and Prevention’s Behavioral Risk Factor Surveillance System.

This survey asks respondents about poor mental health, including stress, depression, or emotional problems, they have experienced in the past 30 days. (The study does not track the same individuals over time – but it can provide a series of snapshots to gauge shifts in a community’s mental health.)

The researchers cross-referenced the survey responses with daily temperature and precipitation data from each participant’s geographical location to reveal the links between weather, climate, and mental health. They found that hotter temperatures and increased precipitation in the short term worsen mental health.

For example, when the average monthly temperatures jump from 25 – 30 °C to hotter than 30 °C, the prevalence of mental health issues increases by half a percentage point. Temperatures over 30 °C are likely to become more common in the US in the coming decades, especially in the South.

During months with more than 25 days of precipitation, mental health problems are 2 percentage points more common than during months with no precipitation. However, how climate change will change precipitation patterns is less certain than for temperature.

Climate warming also takes a chronic toll. The researchers found that a 1 °C increase in average maximum temperature over 5 years is associated with a 2 percentage point increase in mental health difficulties. Not surprisingly, warming during the spring and summer has a bigger impact than increased winter temperatures.

Finally, to determine the mental health effects of climate-related natural disasters, the researchers homed in on the months after August 2005, when Hurricane Katrina made landfall along the US Gulf Coast. “Katrina exposure increased the occurrence of mental health issues by approximately 4% points compared with nondisaster areas,” the researchers write.

Climate change commentators often speak of “brittleness” versus “resilience” to climate change, and the need to “ruggedize” society in preparation. Often, this centers around physical infrastructure such as roads that might be vulnerable to flooding, or food distribution systems that might be vulnerable to drought. But is it possible to make ourselves more psychologically resilient to climate change?

In the new study, mental health difficulties associated with climate change are worse among those with lower incomes. And the researchers point out that this is in the United States, a very wealthy country overall – the psychological impacts of climate change may be more severe and widespread in poorer countries, they say.

That suggests that on the flip side, efforts to reduce poverty are also strategies to increase climate change resilience. And in turn, that shows how more and more, all political issues are really part of the same overarching one.

Source: Obradovich N. et al. “Empirical evidence of mental health risks posed by climate change. Proceedings of the National Academy of Sciences. 2018.

Image: “Melting Men” sculpture by Nele Azevedo.

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