Residential greenness associate with psychiatric problem and physical-psychological multimorbidity among 6900 Chinese...

Psychological problem and physical-psychological multimorbidity is rising among middle-aged and older adults in China. Whether residential greenness, air pollution and systemic inflammation jointly influence psychiatric outcomes remains unclear. Using a retrospective cross-sectional design based on 2015 China Health and Retirement Longitudinal Study (CHARLS) data, we investigated the link between the Normalized Difference Vegetation Index (NDVI) and psychiatric problems/comorbidities, and evaluated the roles of ambient pollutants (PM₂.₅, PM₁₀) and the inflammatory biomarker C-reactive protein (CRP). The final sample included 6900 adults aged ≥ 45 years. Key findings revealed that a 0.1-unit increase in NDVI was associated with an 18% lower risk of psychiatric problems (OR = 0.82, 95% CI 0.68-0.97, P = 0.024) and a 19% lower risk of physical-psychological multimorbidity (OR = 0.81, 95% CI 0.67-0.99, P = 0.035). Conversely, each unit increase in PM₂.₅ and PM₁₀ was linked to a 1% higher risk of psychiatric problems (PM₂.₅: OR = 1.01, 95% CI: 1.00-1.02, P = 0.033; PM₁₀: OR = 1.01, 95% CI 1.00-1.02, P = 0.042) and multimorbidity (PM₂.₅: OR = 1.01, 95% CI 1.00-1.03, P = 0.048; PM₁₀: OR = 1.01, 95% CI 1.00-1.02, P = 0.052). Inflammatory marker analysis showed that a 10-unit increase in CRP was associated with a 20% higher risk of psychiatric problems (OR = 1.20, 95% CI 1.04-1.39, P = 0.013) and a 22% higher risk of comorbidities (OR = 1.22, 95% CI 1.06-1.42, P = 0.007). Pathway analysis confirmed no significant evidence of mediation effects of PM₂.₅, PM₁₀, or CRP on the association between NDVI and physical-psychological multimorbidity. Cross-sectional analyses indicate an inverse association between residential greenness and psychiatric morbidity, yet longitudinal or interventional evidence is required to establish the clinical significance of this relationship and to determine whether air pollution or inflammation represents a causal mediator before findings can guide policy or practice.