Systematic review and meta-analysis investigating nature-based interventions for adolescent mental health: Program characteristics and effectiveness

Rates of psychological distress among adolescents have increased globally, alongside a marked decline in time spent in natural environments. Nature-based interventions (NBIs), structured therapeutic programs involving direct engagement with real, physical natural settings, have emerged as a potentially low-cost and scalable approach to supporting adolescent mental health. However, the characteristics and effectiveness of group-based NBIs for this population have not been comprehensively synthesised. A systematic review and meta-analysis was conducted in accordance with PRISMA 2020 guidelines on peer-reviewed studies published between 2015 and 2025 evaluating group NBIs for adolescents aged 11-19. Eligible designs included quasi-experimental trials with a comparison group and single-group pre-post studies reporting validated psychometric outcomes of mental health or psychological distress. Random-effects meta-analysis was undertaken where possible; when data were unsuitable for pooling, findings were synthesised using Synthesis Without Meta-analysis (SWiM). Program characteristics (e.g., duration, setting, facilitator expertise, and contents) were extracted and narratively synthesised. Twenty-five studies met inclusion criteria. Quasi-experimental designs assessing mental health outcomes demonstrated a large, statistically significant pooled effect ( g = 0.82, 95% CI [0.32, 1.31]). Single-group pre-post studies showed a moderate significant improvement in mental health ( g = 0.60, 95% CI [0.36, 0.85]) and a small but significant reduction in psychological distress was also detected ( g = 0.28, 95% CI [0.04, 0.52]). Narrative synthesis of four studies suggested positive emotional and wellbeing outcomes for some adolescents although findings remain tentative due to incomplete reporting and very small samples. Effectiveness patterns suggest that multi-day immersive programs and those facilitated by practitioners with relevant clinical or specialist outdoor expertise tend to yield the largest benefits. The overall certainty of evidence was low for quasi-experimental studies and very low for pre-post and SWiM evidence. This review was prospectively registered with PROSPERO (CRD420251033171). • Systematic review of group nature-based interventions for adolescent mental health • Synthesises effects on psychological distress and mental health • Nature-based programs show consistent benefits for adolescent wellbeing • Longer and more immersive programs show larger mental health benefits • Challenging programs led by trained facilitators show the strongest outcomes