Urban Greenness, Environmental Indicators, and Major Depressive Disorder Severity: Insights from the FREEDOM Study

This study explores the impact of urban greenness on the severity of Major Depressive Disorder (MDD) within the FREEDOM study, emphasizing the role of environmental indicators in shaping mental health outcomes. A total of 396 MDD patients were recruited at Policlinico Hospital in Milan, where their clinical severity was assessed through multiple psychiatric rating scales. Exposure to urban greenness was quantified using the Normalized Difference Vegetation Index (NDVI) within a 100-meter radius of their residences, while air pollution levels, specifically fine particulate matter (PM2.5) and nitrogen dioxide (NO2), were also considered. Statistical models adjusted for demographic and temporal factors revealed that higher levels of urban greenness were consistently associated with a reduction in depressive symptom severity, including improvements in melancholic symptoms, anxiety, and overall functioning. This beneficial effect appeared to be more pronounced in environments with lower PM2.5 concentrations, highlighting the interplay between vegetation and air pollution in influencing mental health. The findings suggest that urban greenness has a protective role against severe depression, reinforcing the importance of integrating vegetation into urban planning. Future research should focus on advanced three-dimensional indicators of green space to better capture its volume and potential benefits, further refining our understanding of its impact on mental well-being.