A study posted on the website of the University of Chicago (UChicago) suggests a significant link between exposure to environmental pollution and an increase in the prevalence of neuropsychiatric disorders.
The researchers used a U.S. health insurance database of 151 million individuals with 11 years of inpatient and outpatient claims for neuropsychiatric diseases, and compared the geo-incidence of claims to measurements of 87 potential air pollutants from the United States Environmental Protection Agency.
The counties with the worst air quality had a 27 percent increase in bipolar disorder and 6 percent increase in major depression when compared to those with the best air quality. The researchers also found a strong association between polluted soil and an increased risk of personality disorder.
As these correlations seemed unusually strong, the researchers 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 UChicago researchers collaborated with Denmark-based researchers 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.
Analysis of the Danish data is the same as in the United States: a 29 percent increase in bipolar disorder for those in Danish counties with the worst air quality. Using the more specific Danish data, the researchers further found early childhood exposures suggest an even stronger correlation: a 50 percent increase in major depression; a 148 percent increase in schizophrenia; and a 162 percent increase in personality disorders, over individuals who grew up in areas with the highest quality air.
"Our studies in the United States and Denmark show that living in polluted areas, especially early in life, is predictive of mental disorders," said computational biologist Atif Khan, the first author of the new study. "These neurological and 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 study was published on Tuesday in PLoS Biology.
