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 93 empirical studies and 929 bibliometric records to map theoretical advances, methodological evolution, and governance implications in the UGS–MH field. We integrate the following six validated pathways into a unified socio-ecological framework: 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 reveals increasing interdisciplinarity, geographic diversification, and growing attention to dynamic exposure science. Persistent challenges include spatial and temporal misalignment between exposure and outcome measures, reliance on single-modality indicators, limited causal inference, and constrained cross-cultural generalizability. Building on these findings, 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 bridge from evidence to action at the interface of urban sustainability and population mental health.