Here’s why living near busy roads could ruin your mental health

BOSTON — Living near a busy road can elevate the risk of depression in older individuals, a recent study suggests. The significant influence of polluted air on mental health, particularly at the population level, raises considerable concerns as urbanization spreads globally.

The study involved close to nine million participants in the United States, with over 1.5 million developing depression. Those exposed to higher concentrations of pollutants from traffic and industrial sources were found to be most susceptible. A correlation was observed between the incidence of depression and exposure to nitrogen dioxide (NO2), fine particulate matter known as PM2.5, and ozone (O3). NO2 and PM2.5 are primarily emitted from engines, factories, wood-burning stoves, and agriculture, while O3 is produced from their interaction with sunlight during warm summer days.

“Late-life depression should be a geriatric issue that the public and researchers need to be paying more attention to, like on a similar level with Alzheimer’s and other neurological conditions,” says Dr. Xinye Qiu of Harvard University, the study’s lead author, in a media release. “There’s no real threshold [for exposure to air pollution], so it means future societies will want to eliminate this pollution or reduce it as much as possible because it carries a real risk.”

Photo by Roger Victorino on Unsplash

The study followed the participants, all over the age of 64, for over a decade, using insurance claims to identify diagnoses of depression. According to Dr. Qiu, all three pollutants displayed an association with an increased risk of developing depression. To calculate exposure to pollutants, the team used computer models and took into account changes in residential zip codes throughout the years.

“Existing evidence suggests harmful associations between air pollution and neurodegenerative diseases among older adults. However, our understanding of the impacts on late-life mental disorders, such as geriatric depression, is limited. We observed harmful associations between long-term exposure to air pollution and increased risk,” adds Dr. Qiu in JAMA Network Open.

Prior studies in mice suggest that air pollutants inhaled through the nose can reach the central nervous system, inducing inflammation in the brain that may trigger stress hormones associated with cognitive illnesses, including depression. The process of aging could also exacerbate these effects by releasing pro-inflammatory chemicals.

“We hope our study encourages further investigation into potential environmental risk factors, such as air pollution and living conditions, for the prevention of geriatric depression. If we can establish statistically significant associations between depression and modifiable risk factors like air pollution, we could implement preventive population-based solutions, including air quality regulation, emission control, and greener urban planning,” the study authors report.

“You can try and limit it to some degree,” adds Marc Weisskopf, professor of environmental epidemiology and physiology. “But it’s the kind of thing at the population level that really needs regulatory action.”

South West News Service writer Mark Waghorn contributed to this report.

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