Effects of green exercise on mental health: a systematic review and meta-analysis

Introduction: With the increasing global prevalence of mental health issues, green exercise has emerged as a promising intervention, though its effectiveness remains uncertain. This systematic review and meta-analysis aims to clarify the mental health benefits of green exercise by comparing its impact on well-being, positive affect, and negative affect with indoor exercise, built-up exercise, and non-exercise groups. Methods: Fifty-one relevant studies, the outcome data of which were used for the systematic review and meta-analysis, were identified across the PubMed, Web of Science, EBSCOhost, PsycINFO, and the Cochrane Central Register of Controlled Trials databases. Results: The meta-analysis revealed significant effects of green exercise on mental health outcomes. Compared to non-exercise, green exercise significantly improved well-being (SMD = 0.46), positive affect (SMD = [1.18, 1.83]), and reduced negative affect (SMD = [-0.34, -3.38]). Compared to indoor exercise, it significantly improved well-being (SMD = 0.65), positive affect (SMD = [0.68, 1.20]), and slightly reduced negative affect (SMD = [-0.31, -1.38]). Compared to built-up exercise, it significantly improved well-being (SMD = 0.22), had a large effect on positive affect (SMD = [0.59, 1.01]), and slightly reduced negative affect (SMD = [-0.21, -0.57]). Conclusion: Green exercise significantly improves mental well-being, with superior effects on positive affect and reduction of negative affect compared to indoor exercise, built-up exercise, and non-exercise. Future research should explore the long-term effects of green exercise and identify optimal conditions for maximizing its mental health benefits. Syestematic review registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251235047, Registration ID (Unique Identifier): CRD420251235047.