Effect of Forest Therapy on Depression and Anxiety: A Systematic Review and Meta-Analysis

Abstract

This systematic review and meta-analysis aimed to summarize the effects of forest therapy on depression and anxiety using data obtained from randomized controlled trials (RCTs) and quasi-experimental studies. We searched SCOPUS, PubMed, MEDLINE(EBSCO), Web of science, Embase, Korean Studies Information Service System, Research Information Sharing Service, and DBpia to identify relevant studies published from January 1990 to December 2020 and identified 20 relevant studies for the synthesis. The methodological quality of eligible primary studies was assessed by ROB 2.0 and ROBINS-I. Most primary studies were conducted in the Republic of Korea except for one study in Poland. Overall, forest therapy significantly improved depression (Hedges’s g = 1.133; 95% confidence interval (CI): −1.491 to −0.775) and anxiety (Hedges’s g = 1.715; 95% CI: −2.519 to −0.912). The quality assessment resulted in five RCTs that raised potential concerns in three and high risk in two. Fifteen quasi-experimental studies raised high for nine quasi-experimental studies and moderate for six studies. In conclusion, forest therapy is preventive management and non-pharmacologic treatment to improve depression and anxiety. However, the included studies lacked methodological rigor and required more comprehensive geographic application. Future research needs to determine optimal forest characteristics and systematic activities that can maximize the improvement of depression and anxiety.

Mapping of Research in the Field of Forest Therapy-Related Issues: A Bibliometric Analysis for 2007–2021

“…However, most of the primary studies had quality problems or risk of bias, including study design, research process, report quality, and so on ( Stier-Jarmer et al, 2021 ; Yeon et al, 2021 ). Therefore, more detailed and rigorous research is needed in future evidence-based experiments, such as using strict randomized controlled trials and blinded design of experiments, adopting objective physiological indicators (e.g., electroencephalograph and facial action coding system) to assist in confirming subjective psychological outcomes, and focusing on the dose of green space exposure to obtain the maximum effects on health and its durations ( Labib et al, 2020 ; Yeon et al, 2021 ).…”

“…The progressive growth of systemic reviews and meta-analyses suggested that the research showed a tendency from early empirical knowledge to potential non-pharmacological treatments, which will help nature therapy serve as preventive medicine to reduce medical expenditures of the whole society ( Yeon et al, 2021 ; Park et al, 2022 ). However, it is noteworthy that the systematic errors can affect the accuracy of the results of meta-analyses, such as different search strategies, selection criteria, research heterogeneity, and misestimated effect sizes caused by a small number of primary studies ( Mikolajewicz and Komarova, 2019 ; Rojas-Rueda et al, 2019 ; Rosa et al, 2021 ; Stier-Jarmer et al, 2021 ; Yeon et al, 2021 ; Park et al, 2022 ).…”

“…The progressive growth of systemic reviews and meta-analyses suggested that the research showed a tendency from early empirical knowledge to potential non-pharmacological treatments, which will help nature therapy serve as preventive medicine to reduce medical expenditures of the whole society ( Yeon et al, 2021 ; Park et al, 2022 ). However, it is noteworthy that the systematic errors can affect the accuracy of the results of meta-analyses, such as different search strategies, selection criteria, research heterogeneity, and misestimated effect sizes caused by a small number of primary studies ( Mikolajewicz and Komarova, 2019 ; Rojas-Rueda et al, 2019 ; Rosa et al, 2021 ; Stier-Jarmer et al, 2021 ; Yeon et al, 2021 ; Park et al, 2022 ). Accordingly, future meta-analyses should pay attention to the comprehensiveness of the publication language and time in search strategies, the quality of selected articles, and more cautious interpretation of the results ( Mikolajewicz and Komarova, 2019 ; Rojas-Rueda et al, 2019 ; Rosa et al, 2021 ; Stier-Jarmer et al, 2021 ; Yeon et al, 2021 ; Park et al, 2022 ).…”

Does Forest Therapy Have Physio-Psychological Benefits? A Systematic Review and Meta-Analysis of Randomized Controlled Trials

“…In fact, since the measurement of depression in the primary study included in the meta-analysis is not a measurement based on a doctor’s diagnosis, it is an accurate conclusion to state that forest therapy is effective in reducing the symptoms of depression in adults. A study by Yeon et al [ 47 ], which included a quasi-experimental design in meta-analysis, also reported that forest therapy was effective in reducing depression.…”

A Forest Bathing Intervention in Adults with Intellectual Disabilities: A Feasibility Study Protocol

“…The same set of measures will be collected right after finishing the last session (posttest) and seven months after completing the intervention (follow-up) ( Figure 2 ). The timelapse before the follow-up data collection responds to a study recommendation of gathering mid- and long-term measures after a forest bathing-based intervention [ 36 , 37 ]. Since this is an exploratory study, we will take just the mid-term follow-up measures, as we understand that the long-term ones correspond to a full study.…”