Effect of nature-based health interventions for individuals diagnosed with anxiety, depression and/or experiencing stress—a systematic review and meta-analysis

OBJECTIVES: The use of natural environments and nature activities as elements in the treatment and rehabilitation of mental health challenges is gaining international attention. The objective of the present review was to summarise the knowledge on the effects of nature-based health interventions (NBHIs) targeting individuals diagnosed with anxiety, depression and/or experiencing stress. DESIGN: Systematic review and meta-analyses. The quality and certainty of evidence were assessed using the SIGN and GRADE. DATA SOURCES: Searches were performed in Embase, MEDLINE, PsycINFO, CINAHL, Cochrane and Web of Science. ELIGIBILITY CRITERIA: (1) NBHIs, (2) Individuals with a diagnosis of mild to moderate anxiety, depression and/or experiencing stress, (3) Age of participating individuals: 18-84 years, (4) Study designs: randomised controlled trials, cohort studies, case-control studies and case-series studies and (5) Publication date: 2000-2024. DATA EXTRACTION AND SYNTHESIS: Screening, quality appraisal and certainty of evidence, assessed using SIGN and GRADE, were performed by two independent reviewers, except title screening. Meta-analyses were performed using random-effect models. RESULTS: Nineteen articles were included, of which 14 were included in the meta-analyses. The articles showed substantial variation in design, interventions, settings and risk of bias, limiting the certainty of evidence according to GRADE. Participating in NBHIs led to a small to large effect in mental health with standardised mean changes of -0.80 (95% CI= (-1.56; -0.04)), -0.87 (95% CI= (-1.18; -0.56)), -0.32 (95% CI= (-0.74; 0.09)) and 0.58 (95% CI= (0.39; 0.77)) for anxiety, depression and stress scores and overall mental health scores, respectively. CONCLUSIONS: This is the first systematic review examining the effect of NBHIs exclusively on individuals diagnosed with anxiety, depression and/or experiencing stress. Our findings suggest small to large improvements after participating in NBHIs. However, methodological limitations to the included articles necessitate cautious interpretation. PROSPERO REGISTRATION NUMBER: CRD42024516270.