Forest therapy involves engaging in a combination of forest-based activities to improve one’s health or wellbeing. We conducted an overview of systematic reviews (SRs) and meta-analyses of primary studies to provide the most comprehensive summary of the effect of forest therapy on depression. We included 13 primary studies that matched our eligibility criteria - all were included in four recent SRs and were conducted in the Republic of Korea. We carried out meta-analyses with data extracted directly from these 13 studies and assessed their risk of bias. Outcomes of interest were depressive symptoms, temporary recovery from depression (i.e. remission), response to treatment (i.e. ≥ 50 % reduction on depressive symptoms from baseline), adherence to treatment, and adverse effects. Considering pooled estimates from randomized controlled trials with adults, we found that compared to no intervention/usual care, forest therapy produced a greater reduction of depressive symptoms (Hedges’g = 1.18, 95 % CI [0.86, 1.50], p < .00001). Also compared to no intervention/usual care, participants in the forest therapy group were 17 times as likely to achieve remission (Risk Ratio = 17.02, 95 % CI [3.40, 85.21], p = .0006) and three times as likely to have a ≥ 50 % reduction on depressive symptoms (Risk Ratio = 3.18, 95 % CI [1.94, 5.21], p < .00001). Forest therapy, on average, reduced depressive symptoms more than engaging in similar activities in a hospital or non-forested urban area, or participating in an intervention focused on diet plus forest-based exercise. We did not find evidence that adherence to forest therapy is different from the adherence to alternative interventions and the adverse effects of forest therapy appear to be rare. These results indicate that, relative to many more conventional alternatives, forest therapy is a more effective short-term intervention for the prevention and treatment of depression in adults.

森林疗法涉及多种以森林为基础的活动，以改善人们的健康或福祉。我们对主要研究的系统评价（SR）和荟萃分析进行了概述，以最全面地概述森林疗法对抑郁症的影响。我们纳入了13项符合我们入选标准的基础研究-所有这些研究均纳入了最近的四个SR中，并在大韩民国进行。我们使用直接从这13项研究中提取的数据进行了荟萃分析，并评估了其存在偏见的风险。感兴趣的结果是抑郁症状，从抑郁状态暂时恢复（即缓解），对治疗的反应（即抑郁症状从基线水平降低≥50％），坚持治疗以及不良反应。g = 1.18，95％CI [0.86，1.50]，p <.00001）。此外，与不进行干预/常规护理相比，森林治疗组的参与者缓解的可能性是其的17倍（风险比= 17.02，95 ％CI [ 3.40，85.21 ]，p = .0006），是获得缓解的三倍。抑郁症状减少≥50％（风险比= 3.18，95％CI [1.94，5.21]，p<.00001）。平均而言，森林疗法比在医院或没有森林的城市地区从事类似活动，或参与以饮食加森林为基础的干预措施，更能减轻抑郁症状。我们没有发现证据表明坚持森林疗法与坚持其他干预措施不同，而且森林疗法的不良影响似乎很少。这些结果表明，相对于许多其他常规选择，森林疗法是预防和治疗成人抑郁症的更有效的短期干预措施。