An international team of researchers have discovered a strong association between pollution and psychiatric disorders.
Bipolar disorder and major depression in the US and Danish populations were found to be extremely high due to poor air quality, according to the new study. The risk of schizophrenia and personality disorders was particularly high for those exposed to polluted air in the first 10 years of their life in Denmark.
To investigate air pollution exposure among individuals in the US, University of Chicago researchers examined data from the US Environmental Protection Agency's measurements of 87 air quality measurements. In Denmark, researchers used a national pollution register to monitor pollutants that have a higher spatial resolution.
The team also studied two population data sets from both countries. "We strived to provide validation of association results in independent large datasets," study author Andrey Rzhetsky told a news portal.
"Our study shows that living in polluted areas, especially early on in life, is predictive of mental disorders in both the United States and Denmark," the first author of the study and computational biologist Atif Khan told a news portal. Adding, "The physical environment -- in particular air quality -- warrants more research to better understand how our environment is contributing to neurological and psychiatric disorders."
Even though mental issues such as schizophrenia can occur due to genetic predispositions and life experiences, genes alone are not the primary contributing factor. Many scientists believe the interaction between genetic, neurochemical and environmental factors can cause one to develop such conditions.
More and more research in recent years is shedding new light on just how toxic air pollution can be for the brain. A study conducted on rodents found environmental issues like fine dust (particulate matter) can make its way to the brain via the nose and lungs. Researchers have found animals that are exposed to pollution suffer from cognitive impairment and exhibit behaviours linked to depression.
"We hypothesized that pollutants might affect our brains through neuroinflammatory pathways that have also been shown to cause depression-like signs in animal studies," Rzhetsky told a news portal.
However, the findings have created some controversy. "This study on psychiatric disorders is counterintuitive and generated considerable resistance from reviewers," Rzhetsky told a news portal.
"A causal association of air pollution with mental diseases is an intriguing possibility. Despite analyses involving large datasets, the available evidence has substantial shortcomings and a long series of potential biases may invalidate the observed associations," Professor John Ioannidis of Stanford University, told a news portal. Adding, "More analyses by multiple investigators, including contrarians, are necessary."
The study's findings were originally published in the journal PLOS Biology.
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