Forest therapy for psychological stress and emotional disorders: a systematic review and meta-analysis

Forest therapy has attracted growing research interest as a nature-based intervention for mental health. However, the true magnitude and consistency of its benefits remain uncertain, owing to heterogeneous findings across individual studies and notable methodological variability. This systematic review and meta-analysis sought to quantitatively synthesize evidence on the effects of forest therapy on psychological stress and emotional disorders (operationally defined here as depressive and anxiety symptoms), and to explore potential moderating factors. We searched PubMed, Web of Science, Cochrane Library, CNKI, and Wanfang databases through December 2024. Randomized controlled trials and quasi-experimental studies that examined forest therapy interventions using validated self-report psychological outcome measures were eligible. Random-effects models pooled standardized mean differences (SMDs). Heterogeneity was assessed with Q statistics and I² values; subgroup analyses and meta-regression explored candidate moderators. All analyses were conducted in R (version 4.3.2) using the metafor package (Viechtbauer W. J Stat Softw. 2010;36(3):1-48). Twenty-five studies involving 1,876 participants met the inclusion criteria. Forest therapy was associated with reductions in psychological stress (SMD = − 0.71, 95% CI: −0.89 to − 0.53), depressive symptoms (SMD = − 0.68, 95% CI: −0.86 to − 0.50), and anxiety symptoms (SMD = − 0.77, 95% CI: −0.97 to − 0.57). Substantial heterogeneity was present across all outcomes (I² > 74%), and the evidence quality was rated moderate for stress and low for emotional disorder outcomes under the GRADE framework. Among the stress outcomes, subgroup analyses indicated that extended intervention periods and clinical populations were linked to larger effect sizes. Publication bias assessment showed modest asymmetry for emotional disorder outcomes; trim-and-fill adjusted estimates remained statistically significant but were attenuated. Forest therapy appears to be associated with medium-to-large short-term reductions in psychological stress, depressive symptoms, and anxiety symptoms, although high between-study heterogeneity and methodological limitations—particularly the reliance on self-report measures and the impossibility of participant blinding—call for cautious interpretation. The findings tentatively support incorporating forest-based interventions into mental health promotion strategies, especially through sustained, multi-session programs. Longer-term follow-up and more rigorous trial designs are needed before firm clinical recommendations can be made.