Scientists have explained the impact of polluted air on the psyche

Polluted air can affect not only the condition of the lungs and cardiovascular system, but also be associated with changes in mental health. Studies have linked exposure to fine particles and other pollutants to depression, anxiety, and changes in brain function, and new evidence suggests a possible link to suicidal thoughts and attempts. The article "Izvestia" describes how polluted air can affect the psyche, what conditions are associated with exposure to pollutants and why scientists are not yet talking about a direct cause-and—effect relationship.

Not just breathing: what does pollution do to the human psyche?

The impact of air quality on mental health has become a separate area of research in recent years. Scientists are primarily studying fine particles of PM2.5 and PM10, nitrogen dioxide and black carbon. These pollutants are considered in studies as possible factors associated with changes in mental state, however, the degree of evidence of such a relationship varies for different substances and diseases.

In a systematic review and meta-analysis published in the journal Environmental Research, researchers analyzed 81 studies on the association of air pollution with depression and anxiety. The studies included data on short—term exposure to pollutants — less than 30 days - and long-term exposure lasting 30 days or more. The authors found statistically significant associations between both types of exposure and the risk of depression and anxiety.

The European Environment Agency also notes that existing studies have consistently linked air pollution, particularly PM2.5 and nitrogen dioxide, to depression and depressive symptoms. At the same time, experts emphasize that mental health is formed under the influence of many factors, including genetic characteristics, social and economic conditions, lifestyle and psychological circumstances. Therefore, the link between pollution and mental state alone does not prove causality.

Scientists talked about the effect of dirty air on the work of the heart

Why Pollution is associated with depression and anxiety

The possible association of polluted air with depression and anxiety has been studied in the most detail. In the meta-analysis, long-term exposure to all pollutants studied was positively associated with both conditions. For anxiety, the most consistent results were obtained with respect to PM2.5, and for depression, the most pronounced associations were observed for PM2.5 and black carbon.

The authors also found statistically significant associations between short-term exposure to PM2.5, PM10, and nitrogen dioxide and the risk of depression and anxiety. However, the results of individual studies varied, and the quality and uniformity of evidence varied. Therefore, the data obtained primarily indicate a link between exposure to pollutants and mental health, rather than the fact that polluted air directly causes these disorders.

An earlier systematic review published in the journal NeuroToxicology also showed an association of air pollution with anxiety and depressive symptoms. The researchers examined 111 papers on mental health, with 76% of them involving humans and the rest on animals. 73% of the studies noted a greater number of anxiety or depressive symptoms and related behaviors with higher levels of pollution exposure. The most frequently studied were PM2.5, nitrogen dioxide and PM10.

Scientists talked about damage to the oral mucosa due to polluted air

From lungs to brain: how can the mechanism work?

Scientists consider the effects of pollutants on the brain to be one of the possible explanations for the observed connections. In another systematic review of the journal NeuroToxicology, researchers analyzed 92 papers on brain structure and function. In 95% of these studies, statistically significant changes related to pollution exposure were found. Among them, the authors identified signs of inflammation and oxidative stress, as well as changes in neurotransmitters and other substances involved in the nervous system.

The research also affected the hippocampus, prefrontal cortex, and amygdala, areas of the brain associated with emotional regulation and psychiatric disorders. At the same time, PM2.5, ozone and diesel exhaust particles were most often studied. The authors of the review noted that existing data suggest a link between pollution, brain changes, and anxiety or depressive symptoms.

However, there is a significant limitation here: 86% of studies on the structure and functions of the brain have been performed on animals and only 11% on humans. Therefore, the discovered biological mechanisms cannot be directly considered a proven explanation of why a person develops a particular mental disorder when exposed to polluted air. This requires additional research involving humans.

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Are pollutants associated with the risk of suicide

Separately, scientists are investigating a possible link between environmental pollution and thoughts of suicide, self-harm, and deaths. In a systematic review and meta-analysis published in the Journal of Epidemiology & Community Health (JECH), researchers examined work on the effects of air pollution, noise, light, and water. Of the 287 publications selected for detailed review, 45 met the research criteria: 33 were devoted to deaths, seven to suicidal thoughts, and five to attempts.

The majority of the papers — 38 — studied air pollution specifically. The combined statistical analysis includes the results of 29 studies. Scientists have found statistically significant associations between short-term exposure to PM2.5 and PM10, as well as long-term exposure to PM2.5 and nitrogen dioxide, and the risk of deaths, attempted suicide, and suicidal thoughts.

At the same time, the researchers themselves point out the limitations of the work: the number of studies for individual outcomes was small, and the methods and design of the work varied significantly. The experts who commented on the results also stressed that most of the initial data were observational and did not allow us to establish that it was air pollution that caused such conditions or actions. Mental health can simultaneously be affected by socio-economic conditions, urban environment, health status, housing quality, and other factors.

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Connection or reason: what science doesn't know yet

Despite the growing number of studies, scientists are still cautiously assessing the possibility of a direct effect of polluted air on mental disorders. One of the main problems is that people living in areas with high levels of pollution may simultaneously face other circumstances that can affect mental health. Among them are the socio-economic situation, living conditions, access to green areas, features of the urban environment and lifestyle.

In addition, the studies differ in the duration of observation, methods of assessing pollution, and methods of diagnosing mental conditions. The European Environment Agency notes that much of the available work is at a relatively early stage and that more extensive and comprehensive studies are needed to establish cause-and-effect relationships that can take into account related factors.

Thus, current data allow us to consider air pollution as one of the possible factors related to mental health. The most consistent results have been obtained for depression and anxiety, while the mechanisms of exposure and possible links to more severe consequences require further study. Reducing pollution levels is considered by experts as a potentially significant factor in public health, but the mental state of a person cannot be explained solely by air quality.