Ambient air pollution exposure and risk of depression: A systematic review and meta-analysis of observational studies

Recent studies have reported an association between air pollution exposure and depression, with inconsistent results. To address this controversy, we conducted a systematic review and meta-analysis of published observational studies that investigated outdoor air pollution and depression. Five electronic databases were searched, and fifteen articles were finally identified. Pooled odds risks were calculated separately based on pollutant type, exposure duration and outcome. Subgroup analyses were conducted based on design, population, important potential confounders, and pollutants levels. We found a significantly increased risk of depression with long-term exposure to PM_2.5 and short-term exposure to PM₁₀, NO₂, SO₂, CO. No evidence was found in the association between exposure to O₃ and depression. Besides, exposure to high levels of pollutants indicates a higher risk of depression. Our results highlight the necessity of air pollution control for depression. However, further studies with standardized methods are still required to support the results due to the inconsistent results in stratified analyses and methodological limitations of the included studies.