Pollution related to an increase in bipolar disorder and depression



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A new study by researchers at the University of Chicago suggests a significant link between exposure to environmental pollution and an increase in the prevalence of neuropsychiatric disorders.

Based on the analysis of large population datasets from the United States and Denmark, the study, published on August 20 in PLoS Biology, found poor air quality associated with increased rates of bipolar disorder and major depression in both countries.

"Our studies in the United States and Denmark show that living in polluted areas, especially early in life, is a predictor of mental disorders," said computer biologist Atif Khan, the first author of the report. new study. "These neurological and psychiatric diseases – so costly both financially and socially – seem to be related to the physical environment, especially to air quality."

Khan and Andrey Rzhetsky, professor of medicine and human genetics Edna K. Papazian, used a US health insurance database of 151 million people with 11 years of claims for neuropsychiatric diseases in hospital and outpatient settings. They compared the geo-incidence of claims to measures of 87 potential air pollutants from the United States Environmental Protection Agency. Counties with poor air quality had a 27% increase in bipolar disorder and 6% greater depression compared to those with better air quality. The team also found a strong association between polluted soil and an increased risk of personality disorders.

Since these correlations seemed exceptionally strong, the team sought to validate its findings by applying the methodology to data from another country. Denmark tracks environmental quality indicators over much smaller areas (just over a quarter of a mile) than the EPA does. The UChicago team collaborated with Danish 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 diseases in Danish adults who lived in areas where the quality of the environment was poor. until their tenth birthday.

The associations the team found, especially for bipolar disorder, mirrored those in the United States: a 29% increase for those in counties where air quality was the most degraded. Using this more specific Danish data, the team found that early childhood exposures correlated even more strongly with major depression (50% increase); with schizophrenia (an increase of 148 percent); and with personality disorders (162% increase) compared to individuals who grew up in areas where the air is of the best quality.

Researchers have long suspected that genetic and neurochemical factors interact at different levels to influence the onset, severity and progression of these diseases. Until now, scientists have found only modest associations between individual genetic variants and a neuropsychiatric disease: for the most common polymorphisms, the increased risk of disease is low, possibly be less than 10%. This fact has led Rzhetski, who has been studying the genetic roots of a wide variety of neuropsychiatric diseases for more than two decades, to look for other molecular factors that may trigger or contribute to the mechanism of the disease.

Khan, Rzhetsky and the team worked on the project for over two years, improving their models with additional mathematical analysis and data sources. Nevertheless, their results are not without controversy: other researchers in the field have noted that this substantial correlation still does not confirm that pollution actually triggers diseases. Rzhetsky's earlier work on the correlation between air quality and asthma – which used a similar methodology – met with no resistance from journals or the broader scientific community. Rzhetsky adds that, during experiments on animals exposed to pollution, they show signs of cognitive impairment and behavioral symptoms similar to those of depression.

Although the study did not address the question of how air pollution could cause neuronal effects, many experimental studies on animal models suggest that polluting chemicals affect neuroinflammatory pathways and lead the way. subsequent neurodevelopmental issues, many of which occur at the end of the year. childhood when children become adults.

Quote: "Environmental pollution is associated with an increased risk of psychiatric disorders in the United States and Denmark" PLoS Biology August 20, 2019 DOI: 10.1371 / journal.pbio.3000353

Funding: Liz and Kent Dauten, the National Institutes of Health, NordForsk, and the DARPA Big Mechanism Program

-The article originally appeared on the website of the University of Chicago Medicine

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