A recent nationwide study has highlighted a connection between long-term exposure to fine particulate matter (PM2.5) and an increased risk of depression and anxiety, emphasizing the growing mental health burden linked to environmental factors in India.
The study, spearheaded by researchers from IIT-Delhi in collaboration with AIIMS New Delhi, NIMHANS, and St John's Medical College, analyzed data from 34,802 adults across 12 states, including Punjab, UP, Rajasthan, and Assam. The findings, published in the international journal iScience, revealed that prolonged exposure to PM2.5 is associated with an 8% higher likelihood of depression and a 2% increase in anxiety.
It is important to note that the analysis is cross-sectional, drawing upon clinically diagnosed cases from the National Mental Health Survey (2015–16), which means it establishes an association rather than a direct causation. Dr. Anand Krishna from AIIMS emphasized the importance of this distinction, while also pointing out that even modest associations are significant due to the widespread exposure to air pollution.
The study identified specific demographics that are most vulnerable, including urban metro residents, individuals aged 40-49 years, and those from lower-income groups. Regionally, the link between pollution and depression was stronger in eastern India, while anxiety was more prominent in the western region. The post-monsoon season, characterized by increased pollution levels, also saw a peak in mental health risks.
Researchers delved deeper into the chemical constituents of air pollution, pinpointing specific components with stronger links to depression, such as sulfates, nitrates, and ammonium, which are largely generated by traffic, industry, and agricultural activities. Elemental carbon, a marker of diesel and fossil-fuel combustion, was most strongly associated with anxiety.
These findings align with a growing body of global research highlighting the detrimental effects of PM2.5 on mental health. For instance, a systematic review and meta-analysis revealed a significant positive association between PM2.5 exposure and the risk of depression and a marginally significant positive association with the risk of suicide. The study indicated that for every 10 µg/m³ increase in PM2.5, there was a 19% increased risk of depression. Another study using data from the All of Us Research Program found that depression risks were elevated even at PM2.5 levels below the EPA standard of 9.0 μg/m3.
The implications of this study are particularly relevant as the Union Budget increases its focus on strengthening mental health infrastructure. By identifying specific pollution components and vulnerable populations, the study paves the way for targeted interventions and policies to mitigate the mental health impacts of air pollution. This includes stricter regulations on traffic, industrial emissions, and agricultural practices, particularly in urban areas and during high-pollution seasons. Further research is needed to establish causation and explore the underlying mechanisms through which PM2.5 exposure affects mental health.