Air Pollution Linked to Bipolar Disorder and Major Depression

©. LanaElcova

A new study suggests a significant link between exposure to environmental pollution and an increase in rates of neuropsychiatric disorders.

Air pollution is no fun. It is ugly, it literally hurts, and it has been linked to all kinds of health problems, with lifelong effects ranging from loss of lung function to asthma, obesity, diabetes and neurological disorders. And now a new study from the University of Chicago Medical Center adds to pollution's grim bag of tricks by suggesting a link between pollution and neuropsychiatric disorders.

Looking at large population data sets from the United States and Denmark, the researchers found that in both countries, poor air quality was associated with increased rates of bipolar disorder and major depression.

"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, PhD, the first author of the study. "These neurological and psychiatric diseases – so costly in both financial and social terms – appear linked to the physical environment, particularly air quality."

The study's senior author, Andrey Rzhetsky, has been studying the genetic roots of a wide variety of neuropsychiatric diseases for over two decades – but scientists have long suspected that there is more to these illnesses than genetics. This led Rzhetsky to start looking for other factors that might add to or jumpstart the disease mechanism. "What aspects of human environments are driving psychiatric and neurological disease prevalence?" ask the authors.

The researchers started with a U.S. health insurance database of 151 million people with more than a decade of claims for neuropsychiatric diseases. They compared the locations of the claims to measurements of 87 potential air pollutants from the U.S. Environmental Protection Agency (EPA). As the University explains, in the U.S. they found:

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

The connection seemed so strong that they decided to check it against similar data from another country. Denmark tracks their environmental quality more thoroughly than does the EPA, making it a good choice for comparison. For this second part of the study, they analyzed Danish national treatment registers with data from 1.4 million people born in Denmark between 1979 and 2002 – they specifically looked at neuropsychiatric disease in Danish adults who had lived in areas with poor environmental quality up to their tenth birthdays. Again from the University:

The associations the team found, especially for bipolar disorder, mirrored those in the United States: a 29 percent 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 percent increase); with schizophrenia (a 148 percent increase); and with personality disorders (a 162 percent increase) over individuals who grew up in areas with the highest quality air.

The team spent two years working with and improving their models with additional mathematical analyses and data sources. While they point out that a significant correlation does not confirm pollution actually triggers the diseases, it is still pretty sobering. And Rzhetsky says that in research on animals exposed to pollution, the animals show signs of cognitive impairment and depression-like symptoms. (Sorry, animals.)

The research did not delve into how air pollution might be sparking these illnesses, but the authors note that growing evidence from human, animal, and in vitro studies show that airborne pollutants target the brain and are implicated in neurological and psychiatric disorders. The authors conclude that their study sets the stage for more research on the topic, writing, "Our results indicate that the physical environment, in particular air quality, warrants further attention in research seeking to elucidate environmental contributors to neurological and psychiatric disease risk."

The study, "Environmental pollution is associated with increased risk of psychiatric disorders in the US and Denmark," was published in PloS Biology.