Abstract
As mental health challenges continue to rise globally alongside increasing urbanization and treatment barriers, nature-based interventions (NBIs) may provide an accessible, affordable, and low-risk alternative to conventional mental health treatments. This systematic review synthesizes quantitative evidence on the impact of NBIs on mental health outcomes, following PRISMA 2020 guidelines. Randomized controlled trials with a nature-based intervention group and a non-nature control group, reporting at least one mental health outcome, were included. Of 10,113 identified records, 47 trials met the inclusion criteria. Most interventions involved horticultural therapy, green exercise, or nature walks. Seventeen studies reported significantly greater improvements in mental health, particularly depression, anxiety, and stress in NBI groups compared to controls. NBIs showed no evidence of inferiority to established treatments such as cognitive behavioral therapy or art therapy. However, studies varied widely in design, intervention type, duration, and outcome measures, and many showed moderate to high risk of bias. While initial evidence supports the effectiveness of NBIs, future research should prioritize long-term studies, higher methodological quality, and detailed subgroup analyses to better understand the specific conditions under which NBIs are most beneficial, as well as test the added benefits of combining NBIs with established treatments.