Mental illness is linked to economics

Mental illness increases with air pollution

CHICAGO. Living in polluted air is linked to an increased rate of mental illness, researchers from the University of Chicago report. You analyzed insurance data from 151 million US citizens.

Result: In people from regions with particularly poor air quality, the number of cases for bipolar disorder and severe depression was increased (PLOS Biology 2019; online August 20).

Examined frequency of four mental illnesses

The scientists led by Atif Khan and Andrey Rzhetsky examined the frequency of four psychiatric illnesses - bipolar disorder, severe depression, personality disorder and schizophrenia - as well as for the neurological diseases epilepsy and Parkinson's disease.

"These neurological and psychiatric diseases - both financially and socially very costly - seem to be related to the physical environment, especially the air quality," Khan is quoted in a statement from his university.

The researchers compared the health data with the air quality of the respective residential district, which they obtained from information from the US Environmental Protection Agency (EPA).

Results: In regions with the poorest air quality, six percent more people fell ill with severe depression than in areas with particularly good air. In the case of bipolar disorder, the risk of the disease was even increased by 27 percent.

Danish analysis with data from 1.4 million people

In the second part of the study, the researchers then analyzed a Danish treatment and environmental registry, which includes more than 1.4 million people born in Denmark between the beginning of 1979 and the end of 2002. Here, the rate of severe depression in areas with the highest air pollution was a good 50 percent higher than in the particularly clean areas.

The researchers in Denmark also found increased values ​​for the other mental illnesses: the risk of personality disorders was increased by 162 percent and that for schizophrenia by 148 percent. For bipolar disorder, the 24 percent increase was similar to that in the US data.

The authors explain the difference in the results with the difference in the evaluated data: "It is likely that this difference is due to the limited resolution of the pollutant estimates for the US data," they write. But the composition of the pollutants or country-specific genetic variations could also play a role.

Further studies needed

In a comment in "PLOS Biology", John Ioannidis of Stanford University in California criticizes the study as having "significant shortcomings and a long range of possible biases". In the US, for example, the environmental data were measured in the years 2000 to 2005, while the disease diagnoses came from 2003 to 2013.

“These analyzes, as well as subsequent studies in the field, would benefit from rigorous, carefully defined protocols that are registered before the data is analyzed,” writes Ioannidis.

Despite this criticism, Tilo Kircher from the Marburg University Clinic for Psychiatry and Psychotherapy considers the study to be an important contribution to medical research: "It will hopefully trigger further research in this area." The strength of the study is the huge amount of data.

Kircher thinks the results are plausible, although he is astonished that the analyzes of the US data only showed a clear association with air pollution for bipolar disorder.

The expert refers to results from animal experiments, according to which fine dust and pollutants could trigger inflammation in the brain. (dpa)