Air pollution suffocates the lungs and shortens life, but may also be associated with a higher risk of mental illness. This was announced by scientists who analyzed health information for millions of patients in the US and Denmark, according to Reuters and BTA.

People exposed to poor quality air in both countries are more likely to receive diagnoses such as bipolar disorder and depression, according to scientists at the University of Chicago, although some have argued that the work is flawed and more definitive conclusions are needed.

Andrey Rzhetsky, study author and professor of medicine and human genetics at the University of Chicago, said in a statement: “There’s quite a few known triggers but pollution is a new direction.

“Research on dogs and rodents shows air pollution can get into the brain and cause inflammation which results in symptoms resembling depression. It’s quite possible that the same thing happens in humans.”, Standard UK reported.

Scientists have compared health data and pollution indicators in the area to 151 million Americans and 1.4 million Danes. Exposure to childhood pollution is associated with twice as many cases of schizophrenia among Danish patients, as well as more personality disorders and depression.

Among US patients, dirty air is also associated with higher levels of bipolar disorder and depression, but not with other conditions such as schizophrenia, epilepsy, and Parkinson's.

According to the World Health Organization, 7 million people die annually due to dirty air - 13 per minute more than war, homicide, tuberculosis, HIV, AIDS and malaria combined.