Air Pollution Linked to Psychiatric Disorders Like Depression and Schizophrenia

Air pollution has been proven to have a variety of negative impacts on public health — and according to a new study, living in an area with significant air pollution can also negatively impact our mental health. Interestingly, the study found significant associations between air pollution and rates of six psychiatric and neuropsychiatric disorders in both the U.S. and Denmark. And even though the findings are preliminary, it's just one more piece of information showing how the climate crisis affects people — especially those living in poverty.

The study, published Tuesday, Aug. 20 in the journal PLOS Biology, studied four psychiatric conditions: bipolar disorder, major depression, personality disorder, and schizophrenia; it also looked at two neurological conditions: epilepsy and Parkinson's disease. For the U.S. part of the study, the authors studied insurance claims data for more than 151,104,811 U.S. residents between 2003 and 2013. They then studied EPA data on environmental factors, such as quality of air, water, and land, vehicular pollution, weather, and various sociodemographic factors (which are also known to affect psychiatric disorders), and compared the two data sets to look for correlations between pollution and those disorders.

After studying the U.S. data, researchers observed a 27 percent increase in bipolar disorder in people living in areas with poor air quality, a 6 percent increase in major depression in those living in counties with the highest air pollution, and a 19.2 percent increase in the rate of personality disorder in counties with the poorest land quality. 

For the Denmark portion of the study, instead of measuring things by county, the authors looked at air pollution during childhood across the entire country. To do so, the authors studied Danish pollution registers for all 1,436,702 people who were born in Denmark between 1979 and 2002 and still lived there on their 10th birthdays. They then compared exposure to air pollution to development of the four psychiatric disorders (the two neuropsychiatric disorders were not included in the Danish part of the study).

The authors found that the rate of all four psychiatric disorders increased along with increasing air pollution. In areas with poor air quality vs. areas with better air quality, the estimated rates were 148 percent higher for schizophrenia, 24 to 29 percent higher for bipolar disorder, 162 percent higher for personality disrorder, and 51 percent higher for major depression.

These findings echo a January 2019 study that found that young people exposed to poor air quality had a three to four times greater chance of developing depression at age 18, as reported by The Guardian.

All that being said, the authors of this new study emphasize multiple times throughout the paper that their findings do not definitively mean pollution causes these psychiatric disorders. "Increased knowledge of environmental risk factors is therefore vital for a more comprehensive understanding of disease causation," the authors wrote. Additionally, Andrey Rzhetsky, who co-authored the study, told National Geograhpic that while the study is not necessarily proof of a causation between air pollution and mental illness, "it shows where a person might be slightly more at risk." 

Not to mention, mental health disorders often go undiagnosed or unreported, especially in low-income communities where people may not be able to afford treatment — so getting definitive answers on this behemoth topic will require many more comprehensive studies in the future.

In addition to air pollution's possible effects on mental health, air pollution can cause illnesses like strokes, lung cancer, respiratory infections, and heart disease — in fact, in 2016, air pollution was responsible for an estimated 4.2 million deaths worldwide, according to the World Health Organization.