Exposure to air pollutants, especially fine particulate matter and nitrogen dioxide, significantly increases suicidal thoughts and the risk of death by suicide, according to a meta-analysis published today in the Journal of Epidemiology & Community Health.
The results of the study, conducted by the Public Health Centre at Queen’s University Belfast, in the United Kingdom, indicate that environmental factors — especially environmental exposures — should be treated as risk-enhancing factors in suicide prevention strategies.
Therefore, the authors recommend integrating environmental protection and urban planning as essential tools for suicide prevention.
The work recalls that, every year, more than 720,000 people die by suicide worldwide, which led the World Health Organization to develop a Mental Health Action Plan to reduce this global public health issue by at least one third between 2013 and 2030.
The effect of exposure to environmental factors on mental disorders such as depression or anxiety has been extensively studied, but the risk of suicide is less well understood.
To uncover this, the researchers analyzed existing data on environmental, acoustic, luminous, and water pollution, and took into account sociodemographic factors such as sex and income, which could also influence the risk of death by suicide and suicidal behaviors.
After exhaustively searching research databases and studies published in English between January 2010 and April 2024, the authors selected 45 studies (38 on environmental pollution, 3 on acoustics, and 1 on lighting), of which 29 were subjected to a meta-analysis and 16 to a review.
The analysis showed that short-term exposure (less than six months) to fine particulates PM2.5 (13 studies) and PM10 (7 studies) and long-term exposure (more than six months) to PM2.5 (6 studies) and NO2 (7 studies) are related in a statistically significant way to the risk of death by suicide, suicide attempts, and suicidal thoughts.
Moreover, the review revealed associations with other air pollutants, such as sulfur dioxide (SO2), ozone (O3) and carbon monoxide (CO), and with noise pollution.
The limited number of studies prevented assessment of the effects of water and light pollution.
Finally, the analysis found clear associations between the risk of death by suicide or suicidal thoughts and sociodemographic factors.
The authors explain that the fact that pollution influences the risk of suicidal behaviors is due to atmospheric pollutants, including PM2.5, PM10, NO2, SO2 and O3, and water contaminated with arsenic, lead, lithium or nitrate, causing chronic inflammation and nerve damage, which alters brain function and influences mood and stress resilience.
The researchers also note that there is evidence that noise pollution influences some mental health disorders, such as anxiety and depression, and that exposure to environmental noise, such as nighttime or railway traffic, generates chronic stress and alters the circadian clock.
Although the researchers acknowledge several limitations in their findings, among them the small number of studies available on each outcome, they conclude that the results “highlight the crucial importance of recognizing environmental exposures as modifiable risk factors in suicide prevention efforts.”
“The integration of environmental health into mental health policies, through intersectoral collaboration, pollution-reduction strategies and public health interventions, could play a vital role in reducing suicide risk and improving the population’s overall mental well-being,” the authors write.
