Table 1.
Characteristics of included reviews and meta-analyses including key details of the covered primary studies.
| First Author (Date); Country |
Search Details | Objective; | Assessment of Risk of Bias and/or Study Quality: | Number (Type) of Studies Included; | Study Population; | Interventions: Intervention Group (IG) and Control Group (CG); |
|---|---|---|---|---|---|---|
| Meta-Analysis: Yes/No | Total Number (Range) | |||||
| Country of Study Implementation | Intervention Duration | |||||
| Lee (2016); | 6 DBs, from inception to Nov. 2015; | Effects of forest programs on atopic dermatitis; | RoBANS | N = 5 (5 NCT); | Children, adolescents with atopic dermatitis; | IG: forest experience, forest trip; forest camp; physical therapy; forest-camp swimming; forest activities, disease education |
| SB: confounder and selection of participants—high, comparability—predominantly low | ||||||
| South Korea [31] | GL: unpublished dissertations considered | |||||
| PB: high | ||||||
| 184 (12–64) | ||||||
| CG: n. a.; | ||||||
| No | DB: high | Korea | Durations: 1–3 days (3–4 nights) | |||
| LR: n. a. | ||||||
| AB: predominantly low | ||||||
| RB: predominantly low | ||||||
| Ideno (2017); | 4 DBs, from inception to May 2016; | Effects of the forest environment on blood pressure; | RoB | N = 20 (2 RCT, 15 NRCT cross-over, 3 NRCT); | Healthy adults, adults with hypertension; | IG: walking in/sitting in and viewing forest area |
| SB: high (with 50%) | CG: walking in/sitting in and viewing in non-forest environment, such as city areas, sitting in a room, measuring blood pressure in daily life; | |||||
| GL: was searched | PB: high | |||||
| Japan | DB: high | Japan (n = 17) | 732 (6–268) | |||
| [28] | LR: English and Japanese language only | AB: low | Korea (n = 2) | |||
| Yes | RB: low | China (n = 1) | ||||
| Durations: 15 min to 2 h; 1 × 3 days, 1 × 7 days | ||||||
| Lee (2017); South Korea [32] |
7 DBs, from inception to July 2016; GL: n. a. LR: English and Korean language only |
Effects of forest therapy on depressive symptoms; No |
SIGN checklist 18 studies low and 10 acceptable quality |
N = 28 (17 RCT, 11 NRCT); Korea (n = 17) Japan (n = 7) China (n = 3) Great Britain (n = 1) |
Healthy adults, adults with health conditions: alcoholism, COPD, chronic stroke, hypertension, cancer, mental-health conditions, psychiatric out- and inpatients, major depression disorder; 1090 (11–92) |
IG: forest therapy: walking as a key component in the forest, other therapeutic activities (experiencing the forest through all five senses: seeing, hearing, touching, smelling, tasting), viewing the forest/meditation, Qi-Qong, aromatherapy, herbal tea therapy, handicrafts with natural items CG: normal daily routine; conducted same activities in the room/city area/urban forest/hospital/stay in a hotel; regular diet and exercise program in the forest; one-day trip for urban walking; Durations: 12 min to 3 days for 1 day to 12 weeks |
| Oh (2017); Australia [19] |
5 DBs, from inception to Dec. 2016; GL: was searched LR: English language only |
Effects of forest bathing on health; No |
RoB SB: high (with 66%) PB: high DB: high (with 30%) AB: unclear or low RB: low |
N = 6 (6 RCT); China (n = 3) Korea (n = 2) Sweden (n = 1) |
Healthy adults, adults with health conditions: chronic alcoholic, high blood pressure, exhaustion disorders, COPD; 323 (18–99) |
IG: forest-healing camp (interaction with nature; mountain climbing und trekking; self-introspection, including mediation and counselling); mountain-forest walks; forest-rehabilitation group (with subsequent cognitive behavioural rehabilitation for all participants) CG: normal daily routine; walking/hiking/interventions in urban area/city; waiting list group with cognitive behavioural rehabilitation; Durations: 1 h to 2× week for 11 weeks (22 visits each with 4 h) |
| Song (2017); South Korea [34] |
6 DBs, from inception to Dec. 2016; GL: n. a. LR: English and Korean language only |
Effects of forest therapy programs for elementary-school students; No |
RoBANS SB: confounder high (with 50%); comparability—predominantly low; selection of participants—low PB: high DB: high AB: predominantly low RB: predominantly low |
N = 17 (two of them without forest intervention; 10 NRCT, 7 NCT); South Korea |
Healthy children; 1491 (16–308) |
IG: walks; forest athletic meetings; getting along with neighbours; forest-ecology exploration; making something with natural materials; psychotherapy; climate therapy; exercise therapy; diet therapy; water therapy CG: normal daily routine; traditional learning methods, reduced forest program at school; Durations: 5 h to 8 months |
| Chae (2018); South Korea [35] |
5 DBs, from inception to March 2018; GL: n. a. LR: English and Korean language only |
Effects of forest healing therapy; No |
n. a. |
N = 25 (5 of them without forest intervention; 13 NRCT, 12 NCT; Korea |
Nurses, healthcare worker, healthy adults, adults with health conditions: alcoholism, Hwa-Byung, depression, mild cognitive impairment, cancer; 1141 (10–221) |
IG: nature-experiencing physical activities; forest (healing) program; meditation; hiking CG: interventions conducted indoors; other settings (ambulatory treatment); comparator duration of intervention; no intervention; Durations: 1 day to 12 weeks |
| Putra (2018); Indonesia[33] |
2 DBs, from 2007 to July 2017; GL: n. a. LR: English language only |
Effects of phytoncides when forest bathing; No |
n. a. |
N = 10 (n. a.); Japan |
Healthy adults; 126 (12–17) |
IG: walking, sitting and watching in the forest; physical activity; stay in the hotel for 3 days and 3 nights and giving aromatic volatile substances (phytoncides produced by vaporising Chamaecyparis obtusa stem oil) with a humidifier in the hotel room for 3 nights CG: city trips: walking, sitting and watching; normal physical activity; Durations: 4.5 h to 2–3 days |
| Antonelli, (2019); Italy[27] |
6 DBs, from inception to Feb. 2019;GL: was searched LR: English, French, Spanish, and Italian only |
Effects of forest bathing on levels of salivary or serum cortisol as stress biomarkers; Yes |
NIH; RoB SB: low or unclear PB: high DB: low AB: low or unclear RB: low |
N = 22 (3 RCT, 8 RCT cross-over, 5 NRCT, 3 NRCT cross-over,3 NCT);Japan (n = 12) South Korea (n = 4)China (n = 2) Germany (n = 1) Iceland (n = 1), Finland (n = 1) Spain (n = 1) |
Healthy children and adults, adults with health conditions: COPD, high risk of stress/burnout, major depressive disorder, hypertension, post-menopausal women; 2165 (9–348) |
IG: forest bathing: spending time in a forest, walking, resting, watching, and deep breathing in forest; psychological program; cognitive behaviour therapy CG: walking and/or watching an urban area/-park; spending time on beach; no intervention; indoor; psychological program; comparator age; Durations: 15 min to half a day |
| Farrow (2019); USA [30] |
2 DBs, from 2008 to 2018; GL: n. a. LR: n. a. |
Effects of forest bathing on reducing anxiety and heart rate variability (activation of parasympathetic nervous system); No |
n. a. |
N = 10 (2 RCT, 3 RCT cross-over, 1 NRCT cross-over, 1 NRCT, 3 NCT); Japan (n = 8) Taiwan (n = 1) Finland (n = 1) |
Healthy adults, hypertensive adults; 1667 (9–625) |
IG: walking, sitting in forest environment, viewing a forest landscape CG: walking, sitting in urban environment, viewing an urban landscape; Durations: 15 mint half a day (4–4.5h); 15 min on 2 days in a row |
| Wen (2019); China [36] |
3 DBs from 2015 to April 2019; GL: was searched LR: English language only |
Effects of forest environment exposure on human health; No |
Downs and Black Checklist 16 studies high- and 12 studies low-quality; RoB relatively high overall |
N = 28 (7 RCT, 10 RCT cross-over, 1 NRCT cross-over,3 NRCT, 7 NCT); Japan (n = 13) China (n = 6) South Korea (n = 5) Taiwan (n = 3) Poland (n = 1) |
Healthy children, adults, adults with health conditions: high blood pressure, COPD, chronic stroke, chronic heart failure; 924 (6–128) |
IG: exposed to forest (urban forest park), walking, meditation, “five sense experience”, activities and rest, watching the scenery—forest environment, handicrafts, sitting quietly in a dense/sparse forest environment; taking a tree-measuring course; enjoying private time CG: exposed to urban environment/walking and meditating; watching the scenery—urban environment; sitting quietly in a dense/sparse forest environment; indoor classes; Durations: 15 min to 5 days |
| Kotera (2020); United Kingdom [29] |
4 DBs from inception to Oct. 2019; GL: was searched LR: English language only |
Effects of Shinrin-Yoku (forest bathing) and nature therapy on mental health; Yes |
1. NOS 2. Quality Assessment Table of Randomised Controlled Trials RCTs high to medium; RoB in 6 studies low and in 2 studies high |
N = 20 (11 RCT, 2 NRCT, 7 NCT); Japan (n = 10) Korea (n = 4) Taiwan (n = 2) Poland (n = 2) China (n = 1) Serbia (n = 1) |
Healthy adults, adults with health conditons: metabolic syndrome, chronic stroke, psychiatric disorders (depression), chronic diseases, chronic pain, alcoholism; 2257 (12–585) |
IG: Walk in forest and meditation CG: Crossover (forest vs. city); groups with different forest types (birch, maple, and oak); Durations: 15 min to 9 days |
AB: attrition bias; CG: control group; COPD: chronic obstructive pulmonary disease; DB: detection bias; DBs: databases; GL: grey literature; IG: intervention group; LR: language restriction; MA: meta-analysis; n. a.: not applicable or not specified; NCT: uncontrolled trial; NIH: National Institutes of Health; NOS: Newcastle–Ottawa Scale; NRCT: non-randomised controlled trial; PB: performance bias; POMS: Profile of Mood States; RB: reporting bias; RCT: randomised controlled trial; RoB: Cochrane Risk-of-Bias tool for randomised controlled trials; RoBANS: Cochrane Risk of Bias Assessment tool for Non-randomised Studies; SB: selection bias; SIGN: The Scottish Intercollegiate Guideline Network measurement tool; SR: systematic review.