Urban Green Space and Mental Health: Mechanisms, Methodological Advances, and Governance Pathways for Sustainable Cities

Urban green space (UGS) is a critical component of sustainable cities and a modifiable determinant of mental health (MH). This review synthesizes 113 empirical studies and 929 bibliometric records to map theoretical advances, methodological evolution, and governance implications in the UGS–MH field. We integrate six validated pathways into a unified socio-ecological framework, including attention restoration, stress recovery, behavioral activation, physiological regulation, social cohesion, and environmental buffering. Methodological trends indicate a shift from static greenness proxies to street view and multimodal exposure measures, and from cross sectional correlations to models that address spatial heterogeneity, causal identification, and AI enabled prediction. Bibliometric mapping shows increasing interdisciplinarity, geographic diversification, and a growing focus on dynamic exposure science. Persistent challenges include exposure outcome spatial and temporal misalignment, reliance on single modality indicators, limited causal inference, and constrained cross cultural generalizability. Building on these insights, we propose a governance oriented framework to support sustainable and healthy cities through equitable green access, behavior informed planning, nature based interventions, and data driven decision support. Overall, this review strengthens the evidence to action bridge at the interface of urban sustainability and population mental health.