Pollution and depression: identified one of the underlying mechanisms

What links pollutants to our minds?

It damages not only lungs, skin, cardiovascular system, kidneys, metabolism, and reproductive system.

Exposure to air pollution also seems to have negative consequences on mental health: in fact, there are more and more robust scientific studies showing a link between exposure to pollutants and mental problems, including anxiety, psychotic episodes, and depression.

It is precisely with respect to the latter disorder that a team of scientists from the Lieber Insitute for Brain Development in Baltimore, the Institute of Mental Health in Beijing, and other research institutions has recently spoken out: as they recount in a study published in the Proceedings of the National Academy of Sciences, the experts have in fact identified a mechanism by virtue of which exposure to air pollutants could trigger depression in individuals genetically predisposed to the disease.

The study in Beijing

To investigate the phenomenon, the authors of the paper analyzed the genetic makeup of 352 healthy volunteers, all living in Beijing, looking for markers known to be associated with the development of depression.

In doing so, they calculated for each of them what is known as a “polygenic risk score,” a magnitude that expresses the mathematical probability, based on genetic factors alone, that a subject may suffer from depression at some point in his or her life. The choice to conduct the study in Beijing is not accidental: although it is a city with a large population, its population is in fact quite homogeneous from a genetic point of view.

A factor that greatly simplifies experiments of this kind, since it minimizes the role of other genes that might make the results more confusing.

The role of pollution

At this point, the researchers cross-referenced each participant’s polygenic depression risk score with data on air quality around their homes obtained from monitoring stations scattered throughout the city.

Coincidentally, among other things, shortly before the study began, Beijing municipality introduced regulations to reduce pollution by closing the most polluting plants and replacing coal-fired fuels with natural gas fuels.These measures, implemented incrementally, caused a kind of “gradient” in air quality, which was found to be highly polluted in some areas and significantly healthier elsewhere.

To monitor in real time whether and how pollution exposure had an effect on mental health, the researchers also subjected the experiment participants to functional magnetic resonance imaging and cognitive tests specifically designed to assess a state of possible depression.

A multiplicative effect

These are the results of the study: subjects with low polygenic risk and low exposure to pollution scored higher in performing cognitive tests; in contrast, subjects with high polygenic risk of depression reported lower scores on average, particularly if they lived in particularly polluted areas.

Which suggests a rather clear conclusion: pollution has a “multiplicative effect” on depression, probably because it activates genes linked to the disorder and amplifies its effects of emotional and cognitive confusion. All the more reason to take care of our environment and remember that the air we breathe plays a crucial role in our health, both physical and mental.

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