The Effects of Forest Therapy on Immune Function.

Youngran Chae,Suyoun Park,Soyean Kang,Hyoyoung Kang,Sunhee Lee,Youngmi Jo

doi:10.3390/ijerph18168440

Abstract

We conducted a systematic review of the effects of a forest therapy program on adults’ immune function. We used PICO-SD (participants, interventions, comparisons, outcomes, study design) to identify key items. The participants were adults over the age of 18 and the intervention was forest therapy. Our comparisons included studies that comparatively analyzed urban groups or groups that did not participate in forest therapy intervention. Cases without control groups were also included. Immunological outcome measures were included in measuring intervention outcomes. All experimental studies, such as randomized controlled trials (RCTs), non-equivalent control group designs (non-RCTs), and one-group pretest-posttest design were included in the study design. A total of 13 studies were included for comparison. Forest therapy programs were divided into lodging-type and session-type programs. The representative measures for evaluating the effects of immune function were the number of NK cells, the cytotoxic activity of NK cells, and cytotoxic effector molecules. Most studies reported improvement in these measures when comparing values after intervention with values before the forest therapy intervention. Therefore, forest therapy has been found to be effective in improving immune function. More RCT studies on the effects of forest therapy on immune function are necessary.

Highlights

Key items of the criteria for selecting existing studies for this study, were composed according to PICO-SD: (1) The participants were adults aged over 18 years; (2) The intervention included forest therapy; (3) That the studies compared forest therapy groups, with groups that did not participate in forest therapy intervention or urban groups, and cases without control groups were included; (4) Outcomes of the intervention included immunological outcome measures, and (5) In terms of study design, all experimental studies, such as randomized controlled trials (RCTs), non-equivalent control group designs (Non-RCTs), and one-group pretest-posttest design were included
We considered the number of NK cells, NK activity, and cytotoxic effector molecules as measures to evaluate forest therapy’s effects on immune function
The results of this review recommend the use of the number or activity of NK cells for evaluating the effects of forest therapy on immune function, and cytotoxic effector molecules are thought to serve as effective outcome measures

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Forest therapy creates a state of physical relaxation by exposing a participant to a natural environment. It is thought to activate compromised immune function and improve immune function for maintaining and promoting health [1]. Forest therapy makes use of various elements of the forest environment to help individuals cope with stress and to maintain and promote their health [1]. As awareness of forest therapy has increased, so has the number of individuals participating in this therapy [2]. As stress levels have escalated and public frustration caused by social distancing mandates during the COVID-19 pandemic has increased, public interest in forest therapy has increased

Methods

Discussion

Conclusion