As climate change worsens, mental health will probably do too – Quartz

On October 8, a consortium of 90 scientists from 40 countries issued a report warning that inaction could lead to catastrophic climate change over the next 20 years (paywall). The same day, an article published in the Proceedings of the National Academy of Sciences by researchers at MIT, Harvard, and other renowned American research institutes concluded that climate change could potentially worsen large-scale mental health. And such changes may already be measurable in the American population.

The team used responses from the United States Centers for Disease Control's extensive US Adult Health Survey, which sampled randomly selected US residents each year. A question from the survey asks people about their mental health:

"Now think about your mental health, which includes stress, depression and emotional problems, how many days in the last 30 days, how bad was your mental health?"

Researchers used survey responses from 2002 to 2012, involving approximately 2 million participants. Since the survey included data on the respondents' place of residence and the date they answered the question, the team was able to relate the results to historical weather data.

They found that on average, each additional warming of 1 degree Celsius over five years was associated with a 2% increase in mental health problems in these areas. In already warm areas, where the average monthly temperature is between 25 ° C and 30 ° C, the simple switch to a monthly average temperature above 30 ° C has added 0.5% additional mental health problems. To the population.

To examine the impact of extreme weather disasters on mental health, they examined the effects of Hurricane Katrina. The storm has increased the prevalence of mental health problems among people affected by 4%, they found.

AP Photo / Kathy Willens

They also found that, on average, warmer temperatures hurt the most the mental health of low-income people. Women, on average, were also more affected than men. Given that these data were about people living in the United States – a rich country with a relatively mild climate – they note that countries "characterized by a less temperate climate, insufficient resources and greater dependency on in regard to ecological systems can see the more serious effects of climate change on mental health. "

Of course, the survey responses do not indicate clinically diagnosed mental health issues. However, since mental health problems are often not diagnosed in a clinical setting, researchers note that survey responses have the advantage of including distress cases that would otherwise go under the statistical radar.

In addition, the study is about correlation, not about causality – we still do not know conclusively what the climate can do, if any, for cause mental distress. Exposure to more extreme weather conditions "may produce physiological stressors precipitating poor mental health", or "such extremes may trigger inflammatory processes that deteriorate mental health", hypothesized researchers.

Or, they write, the effects can be "entirely due to a reduction in health-maintaining behaviors, such as exercise and sleep." Research is already linking nocturnal warming with the degradation of sleep quality, for example. And warmer summers in the southern states should already result in (pdf) less exercise. However, additional research is needed to truly determine the cause of the deteriorating mental health found in this study.

"Given the vital role that good mental health plays in personal, social and economic well-being, as well as the ability to meet pressing personal and social challenges, our results provide further evidence that climate change poses risks. for human systems, "said the president. the researchers write.

This is not the first indication that mental health problems could come from climate change: a consortium of scientists called the Climate Impact Lab has published peer-reviewed studies that have found higher temperatures to increase suicide rates (pdf) in the United States, Mexico and India.

Reuters / Issei Kato

In the India study, reported by the Guardian, researchers found that suicides increase, especially when heat damages crops during a given growing season. When it is warmer than 20 ° C (68 ° F), each degree increase in one day corresponds to about 70 additional deaths, which implies a warming of the temperature in about 59 300 suicides in India over a period of 30 years.

In 2017, the American Psychological Association published a 69-page literature review that identified "eco-anxiety" as a legitimate mental health problem, highlighting that disasters such as "daily desperation" of Prolonged drought or more insidious changes such as food shortages, sea-level rise and the gradual disappearance of natural environments "will result in some of the most resounding chronic psychological consequences".

"Long-term and gradual climate changes can also bring out different emotions, including fear, anger, feelings of helplessness or exhaustion," the association wrote.