Increasingly, scientists around the world are focusing their research on the connection between environmental conditions and psychiatric and neurological responses.
Now, an international team of experts has analyzed data from 151 million people in the US and 1.4 million people in Denmark , finding that there is a strong correlation between poor air quality and high rates of disorder. bipolar, schizophrenia, personality disorders and major depression. This suggests that there is a link, but it does not necessarily mean that the contamination is causing it.
When the team examined health insurance claims in the United States they found that the strongest predictor of being diagnosed with bipolar disorder, after ethnicity, was air quality. Previous studies have found a correlation between contaminated areas and adolescents with psychotic experiences.
How consistent is the evidence?
Mounting evidence is beginning to provide information on how components of air pollution can be toxic to the brain; however, the study has not been without controversy.
One problem is the lack of data on what an individual’s true exposure to air pollution has been, as some research looks at air quality measurements across the city rather than in specific areas. This represents a great weakness since we know that exposure to air pollution can vary significantly from one street to another adjacent street.
In the new study, exposure in the United States is analyzed at the county level, taking into account that some have an area of thousands of square kilometers.
The study tried to account for confounding factors about available data, including income, ethnicity, and population density. But one obvious factor that could be related to both mental health and pollution could be traffic noise , which is known to increase stress and disrupt sleep.
So how seriously should we take the link between air pollution and mental health?
While the evidence is not yet very strong, experts say it shows that there is an association between polluted air and mental disorders that warrants further investigation.
How could pollution affect our brain?
Some of the smallest pollutants, particles known as PM2.5 , can cross the blood-brain barrier and potentially affect the brain. Another possibility is that increased inflammation in the body, which is known to cause air pollution, can ignite the brain’s stress response. A third possibility is contamination that causes epigenetic changes, affecting DNA activity, and perhaps leading to altered levels of brain chemicals.
Because it is important?
If polluted air were found to be causing mental disorders, “it would open up new avenues for the prevention and treatment of mental conditions,” writes John Ioannidis of Stanford University in PLOS Biology .
What is being done to obtain more information?
The two key things that need to be addressed are studies looking at exposure to polluted air over longer periods of time and a much better geographic resolution, with the help of people wearing individual pollution monitors. Fortunately, such an investigation is ongoing.
Expert opinions
Daniel Maughan of the Royal College of Psychiatrists, who was not involved in the study, told the Science Media Center :
“This paper is based on growing evidence for a link between air pollution and the development of mental illness. While the study does not show that air pollution causes mental illness , it does suggest that there is a strong link between early exposure. air pollution and an increased risk of developing several different mental illnesses, such as schizophrenia, bipolar, depression, and personality disorder. However, there are many environmental factors that could contribute to poor mental health for people living in areas high pollution, such as population density and decreased access to green spaces, making it difficult to isolate poor air quality as the cause of mental illness.
“The College would welcome further research to help increase our understanding of how toxins in the air interact with the brain and how that might affect brain function,” concludes Maughan.
Referencia: SHORT REPORT: Khan A, Plana-Ripoll O, Antonsen S, Brandt J, Geels C, Landecker H, et al. (2019) Environmental pollution is associated with increased risk of psychiatric disorders in the US and Denmark. PLoS Biol 17(8): e3000353. https://doi.org/10.1371/journal.pbio.3000353 PRIMER: Ioannidis JPA (2019) Air pollution as cause of mental disease: Appraisal of the evidence. PLoS Biol 17(8): e3000370. https://doi.org/10.1371/journal.pbio.3000370
