Air pollution linked to high risks of bipolar disorder, depression

In a new study, researchers found a strong link between exposure to environmental pollution and higher risks of neuropsychiatric disorders.

They found in the United States and Denmark, poor air quality is linked to increased rates of bipolar disorder and major depression.

The research was led by a team from the University of Chicago.

The team used a U.S. health insurance database of 151 million individuals with 11 years of inpatient and outpatient claims for neuropsychiatric diseases.

They compared the geo-incidence of claims to measurements of 87 potential air pollutants from the United States Environmental Protection Agency (EPA).

They found the counties with the worst air quality had a 27% increase in bipolar disorder and a 6% increase in major depression when compared to those with the best air quality.

The team also found a strong association between polluted soil and an increased risk of personality disorder.

Because these correlations seemed unusually strong, the team sought to validate their findings by applying the methodology on data from another country.

Denmark tracks environmental quality indicators over much smaller areas (a little over one-quarter of a mile) than does the EPA.

The team collaborated with Denmark-based researchers Aarhus to analyze Danish national treatment registers with data from 1.4 million people born in Denmark between 1979 and 2002.

The researchers examined the incidence of neuropsychiatric disease in Danish adults who had lived in areas with poor environmental quality up to their tenth birthdays.

They found a 29% increase for those in counties with the worst air quality.

Using this more specific Danish data, the team found early childhood exposures correlated even more strongly with major depression (a 50% increase); with schizophrenia (a 148% increase); and with personality disorders (a 162% increase) over people who grew up in areas with the highest quality air.

The team says the research in the United States and Denmark shows that living in polluted areas, especially early in life, is predictive of mental disorders.

These psychiatric diseases—so costly in both financial and social terms—appear linked to the physical environment, particularly air quality.

While the study did not address the question of how air pollution might trigger neural effects, a large body of experimental studies in animal models suggests that polluting chemicals affect neuroinflammatory pathways and set the stage for later neurodevelopmental problems—many of which occur at the end of childhood as children become adults.

The lead author of the study is computational biologist Atif Khan, Ph.D.

The findings are published in PLOS Biology.

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