A nationwide epidemiological study on the associations between ambient particulate matter and suicide in Finland

Growing evidence suggests that air pollution is associated with an increased risk of suicide, albeit with a limited understanding of the mechanisms. Here we examine the short-term association between suicide and particulate matter with a diameter ≤10 µm (PM₁₀) or ≤2.5 µm (PM_2.5) using a time-stratified case-crossover design and nationwide data from Finland from 1985 to 2014, including 35,534 suicides, and investigate whether the association differed by demographic, spatial and temporal factors. We observed immediate associations for particulate matter (odds ratio for suicide per 5.64 µg m⁻³ increase in PM_2.5 from the current day (lag0) of 1.010 and 95% confidence interval 1.000–1.020, estimated from single lag models), with a greater magnitude of the associations in the warm season. The associations between exposure to particulate matter and suicide were particularly evident among males, people under 65 years of age and those who died by suicide using violent methods, particularly during the warm season. Our findings help to better understand susceptibility changes and vulnerable subpopulations in the PM–suicide association and improve mental health promotion programs.