A Systematic Review of Randomised Controlled Trials on the Effectiveness of Ecotherapy Interventions for Treating Mental Disorders

Background: Systematic reviews on ecotherapy interventions (i.e. environmental therapies and animal-assisted therapies) in the general population have demonstrated promising findings. However, there is a need for systematic assessment of the evidence for the use of these interventions in people living with mental disorders. Hence, we conducted a systematic review of randomised control trials (RCTs) on exposure to ecotherapy interventions (i.e. environmental therapy, animal-assisted therapy, wilderness therapy) for individuals with mental disorders. Methods: The search was completed in September 2019 and comprised: Science Direct, PubMed Central, EBSCOHOST (via Academic Search Premier), the Cochrane Library, and Google Scholar. The primary outcomes that were assessed include treatment efficacy (on the CGI-I or similar), symptom severity, and/or dropout rates. Secondary outcome measures assessed included self-efficacy, perceived control, hope, quality of life, life skills, and coping. Results: A total of 2415 reports were identified, of which 94 were assessed for eligibility. Eight environmental therapy trials (i.e. gardening, forest therapy, horticultural therapy, nature adventure rehabilitation, and adventure-based therapy) and ten animal-assisted therapy trials (i.e. dogs, horses or dolphins) were included in the review. Risk of bias assessment was conducted, and qualitative analysis performed to describe the efficacy of the RCTs. The findings suggest that environmental therapies or animal-assisted therapies are efficacious in reducing symptoms of anxiety, depressive, substance-related and addictive, schizophrenia-spectrum and trauma- and stress-related disorders. Conclusion: There is suggestive, but not conclusive, evidence for the efficacy of some eco-therapy interventions in mental disorders. In particular, there are four environmental therapy trials and five animal-assisted therapy trials for depression and/or anxiety; one environmental therapy trial for post-traumatic stress disorder; three environmental therapy and animal-assisted therapy trials for general psychiatric disorders; one environmental therapy trial and two animal-assisted therapy trials for substance use disorders; and, one environ-mental therapy and two animal-assisted trials for people living with a schizophrenia spectrum disorder. The use of standard reporting guidelines may improve evidence quality of future ecotherapy RCTs, and provide a foundation meta-analysis of the evidence.