Air pollution linked to higher suicide risk, but experts warn against assuming cause

People living with high levels of air pollution face a greater risk of suicidal thoughts, suicide attempts, and dying by suicide, according to a new analysis of international research.

Scientists at Queen's University Belfast pooled data from 29 studies conducted worldwide to examine how environmental factors affect mental health. They found that both short- and long-term exposure to fine particulate matter, known as PM2.5, and long-term exposure to nitrogen dioxide—pollutants heavily linked to road traffic and burning fossil fuels—were associated with significantly higher odds of suicidal behaviour.

The research, published in the Journal of Epidemiology and Community Health, also pointed to possible risks from other pollutants. A wider review of 16 further studies suggested potential links to sulphur dioxide, ozone, and noise pollution. However, the evidence for water and light pollution was either too inconsistent or too limited to draw clear conclusions.

Globally, more than 720,000 people die by suicide every year, according to the World Health Organization. It is the third leading cause of death among 15- to 29-year-olds. The WHO has set a target to reduce global suicide rates by one-third between 2013 and 2030.

The Belfast researchers argued their findings mean environmental exposures should be treated as "modifiable risk factors" in suicide prevention policies. They suggested that reducing pollution through cross-sectoral collaboration could help improve overall population mental wellbeing.

Biologically, the connection is plausible. The researchers noted that air pollutants have been linked in other studies to chronic inflammation and nerve damage, which can impair brain function and alter mood. Noise and light pollution are also known to disrupt sleep cycles and increase stress.

However, independent experts have urged strong caution, pointing out that the study shows a statistical link rather than a direct cause.

Dr Jon Van Niekerk, chair of the general adult faculty at the Royal College of Psychiatrists, said that while the study adds to the evidence, the underlying research is observational. "This study cannot establish that air pollution itself causes suicidal thoughts or attempts," he said, adding that dirty air is heavily concentrated in areas with socioeconomic deprivation, poor housing, and poor physical health.

Other scientists agreed that the study fails to untangle these closely related social factors. Alexander Larcombe, an associate professor at Curtin University, noted that highly polluted areas tend to have higher unemployment, more social isolation, and poorer access to mental healthcare.

Dr Rosie Cornish, a senior research fellow in epidemiology at the University of Bristol, pointed out that if air pollution is not a direct cause, cleaning up the air will not prevent suicides. "The authors do not acknowledge this when drawing their conclusions," she said.

Dr Stephen Burgess, a biostatistics professor at the University of Cambridge, said the paper "confuses two fundamentally different concepts: causation and association." He argued that areas with high pollution differ in many other ways that could explain the higher suicide rates, and that much more research is needed before claiming a direct causal link.