Effects of Forest-Based Interventions on Mental Health: A Meta-Analysis of Randomized Controlled Trials.

Forest-based interventions are a promising alternative therapy for enhancing mental health. The current study investigated the effects of forest therapy on anxiety, depression, and negative and positive mental condition through a meta-analysis of recent randomized controlled trials, using the PRISMA guideline. Of 825 articles retrieved from databases including PubMed, EMBASE, CINAHL, Cochrane, and PsycINFO, 6 met the inclusion criteria. The results of this study showed that forest-based interventions improved the mental health of participants in the intervention groups when compared to those in the control groups. Thirty-four outcome variables were analyzed from six studies. The overall effect size of the forest therapy programs was 1.25 (95% CI = 0.93−1.57, p < 0.001), which was large and statistically significant. These findings imply that forest-based interventions can improve mental health as a nonpharmacological intervention. This study is significant in that it is a meta-analysis of mental health that included only high-quality domestic and international RCTs. In future studies, more RCTs related to various forest interventions and studies involving many participants should be undertaken, which will complement heterogeneity in future meta-analysis studies.