The burden, drivers, and inequalities of depression attributable to fine particulate matter from 1998 to 2021: a global analysis

To date, there is a lack of studies that systematically assess the depression burden attributable to fine particulate matter (PM_2.5), its associated driving factors, and the evolving spatial inequalities therein. Using an exposure attribution method, we estimated the PM_2.5-attributable depression burden and associated drivers for 204 countries in 1998–2021. Results reveal that the depression cases attributable to PM_2.5 increased from 33.448 million (95% CI: 10.538–55.674 million) in 1998 to 65.759 million (95% CI: 21.096–108.470 million) in 2021, primarily driven by population growth (44.8%), rising pollution (28.9%), and an increasing prevalence of depression (26.3%). The burden was primarily concentrated in Africa and Asia, which together accounted for approximately 89.2%, and was significantly higher in the Southern Hemisphere compared to the Northern Hemisphere. Region-specific drivers varied: population growth was the primary driver in Africa, whereas the combined influence of population growth and rising PM_2.5 concentrations drove the burden in Asia and South America. Europe was the only region to experience a decline due to a consistent decrease. The PM_2.5-attributable depression burden was negatively associated with per capita GDP and the proportion of the population aged 65 and above, highlighting a paradoxical relationship where developed nations exhibit higher depression prevalence but lower attributable burdens. The global Gini coefficient for attributable depression burden rose from 0.358 in 1998 to 0.377 in 2021. Notably, low-latitude regions maintained persistently high inequality, whereas high- and mid-latitude regions showed more pronounced increases in spatial inequality, primarily driven by widening gaps in PM_2.5 exposure. These increasing disparities highlight the need for region-specific air pollution control strategies to promote global mental health equity.