Nature-Based Programs May Help Mental Health, Evidence Uncertain
Adults diagnosed with anxiety, depression, or stress participated in structured nature-based interventions, which were associated with improvements in some mental health outcomes.
Structured programs in natural settings were linked to reductions in anxiety and depression symptoms and moderate improvements in overall mental health in adults with diagnosed conditions, though results were inconsistent and the evidence was rated very low certainty, according to a systematic review and meta-analysis. The analysis included 19 studies published between 2000 and 2024 that evaluated nature-based health interventions (NBHIs) in participants aged 18 to 84 years with mild to moderate anxiety, depression, or stress-related conditions. Fourteen of these studies were included in the meta-analyses. NBHIs took place in green or blue spaces—such as parks, forests, therapy gardens, and coastal areas—and were delivered by trained health professionals over one to 24 weeks. The review found a large reduction in depression symptoms, with a standardized mean change of −0.87, based on six studies. Anxiety symptoms were also reduced, based on three studies. A small, non-significant reduction in stress was observed . Seven studies showed a moderate improvement in overall mental health. The interventions included multiple sessions and involved structured activities such as nature walks, therapeutic horticulture, forest therapy, and sea swimming. Session counts ranged from 5 to 96. Most interventions were group-based and required repeated exposure to nature. Eight of the included studies were randomized controlled trials, and 11 were cohort studies. The quality of evidence was rated low to moderate. Most studies lacked blinding and showed variability in outcome reporting, study design, and participant characteristics. According to the GRADE system, the certainty of evidence was rated as very low for all outcomes due to risk of bias, heterogeneity, and imprecision. Across the 19 studies, 45 different mental health outcome measures were identified. Most were patient-reported symptom scales for anxiety, depression, stress, and general well-being. Three of five randomized trials that assessed overall mental health found significantly greater improvements in NBHI participants than in control groups. However, two randomized controlled trials showed no significant differences between groups. The findings suggest that NBHIs may serve as complementary strategies in mental health care,although the evidence is of very low certainty and results were not consistent across all trials. The authors called for more rigorous trials to determine which types of NBHIs are most effective, for whom, and under what conditions. Further research is also needed to clarify the underlying psychological and physiological mechanisms associated with nature exposure. The authors reported no conflicts of interest. Source: BMJ Open
