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Table 1 Characteristics of the trials included in the systematic review

From: Health and well-being benefits of spending time in forests: systematic review

Author Year
Study design, Location Sample size, age Study population Intervention group Duration of intervention Control group Outcome Measurement Results and conclusion
Shin et al. [1] 2012
Environ Health Prev Med
RCT Korea N = 92
Age (mean 45.26 ± 3.89 years); gender (84 males, 8 females)
Chronic alcoholic
N = 47
The 9-day forest healing camp
3 days: interaction with Nature
3 days: challenge including mountain climbing and tracking
3 days: self-introspection including mediation and counseling
9 days N = 45
Normal daily routine
Depression measured with Beck Depression Inventory (BDI) There was a significant difference between two groups (t = − 6.27; p ≤ 0.001) in favor of forest camp group.
Forest environment has a potential effect on depression of chronic alcoholics.
Mao et al. [2] 2012
Journal of Cardiology
RCT China N = 24
Aged from 60 to 75 years
Patients with diagnosed essential hypertension. BP, with or without medical control, less than 180/110 mmHg
N = 12
Mountain forest
Participants walked at an unhurried pace for about 1.5 h, with a 20-min rest during the walk in the morning and afternoon (total 3 h walk/day), They were allowed to do as they wished in the hotel, though avoiding strenuous exercise and any stimulating activities in their hours of relaxation before sleeping.
7 days 7 nights. N = 12
Urban area
Same amount of walking hour intervention at city.
BP with mercury sphygmomanometer
Cytokines [interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α) were analyzed with radioimmunoassay kits
Cardiovascular disease associated
factors: endothelin-1 (ET-1), homocysteine (Hcy), renin, angiotensinogen
(AGT), angiotensin II (Ang II), angiotensin II type 1 receptor (AT1) and angiotensin II type 2 receptor (AT2) in sera were measured with enzyme-linked immunoassay
Mood status were measured with POMS
Air quality, concentration of PM10 (particulate matter considered as mass defined by size cutoff at 10 μm in aerodynamic diameter) was measured by a portable laser dust monitor
Subjects exposed to the forest environment showed a significant reduction in blood pressure in comparison to that of the city group (p < 0.05).
The serum IL-6 level was significantly reduced in the forest-bathing group compared with its baseline level but not in city group. However, the TNF-α level remained unaltered in both groups during the experiment.
The values for the bio-indicators in subjects (ET-1, Hcy, AGT, AT1) exposed to the forest environment were also lower than those in the urban control group (p < 0.05).
The POMS evaluation showed that subjects had lower scores in the negative subscales, and increased score for vigor in the forest environment group.
The air quality in the forest environment was much better than that of the urban area.
Forest bathing has therapeutic effects on human hypertension and induces inhibition of the renin–angiotensin system and inflammation, and thus inspiring its preventive efficacy against cardiovascular disorders.
Mao et al. [3] 2012
Biomedical and Environmental Sciences
RCT China N = 20
Mean age 20.79 ± 0.54 years
Normal male university students
N = 10
Mountain forest Participants walked at an unhurried pace for about 1.5 h, with a 10-min rest during the walk. In the afternoon, after taking lunch in the resting room, the participants walked another area at an unhurried pace for about 1.5 h, with a 10-min rest during the walk.
2 days N = 10
Urban area Same hour walking intervention at city.
Superoxide dismutase (SOD) was examined according to the xanthine oxidase method using a standard assay kit.
Lipid peroxidation was evaluated by measuring MDA concentrations
Cytokines IL-6, TNF-α, and ET-1 were analyzed with radioimmunoassay kits.
Cortisol and testosterone levels in serum were measured with chemiluminescent immunoassay.
Lymphocyte assay: To determine lymphocyte subsets, CD5+/CD19+ (B cells), CD3+ (T cells), CD3+/CD4+ (T-helper cells), CD3+/CD8+ (T suppressor cells), and CD3−/CD16+/CD56 + (NK cells), Mood status were measured with POMS
Subjects exposed to the forest environment showed reduced oxidative stress and pro-inflammatory level were as evidenced by decreased MDA, IL-6, and TNF-α levels compared with the urban group (p < 0.05). Serum cortisol and testosterone levels were also lower than in the urban group (p < 0.05). The concentration of plasma ET-1 was much lower in subjects exposed to the forest environment (p < 0.01). The POMS evaluation showed that after exposure to the forest environment, subjects had lower scores in the negative subscales, and the score for vigor was increased (p < 0.05). Exposure to the forest environment, even for a short time, may have positive impact on human health.
Lee et al. [4] 2014
European Journal of Integrative Medicine
RCT Korea N = 70
Intervention group mean age: 70.19 ± 4.66
Control group mean age: 71.11 ± 5.80
Elderly femal
N = 50
Forest walking
1 h in the morning N = 20
City walking
Arterial stiffness was measured with the cardio-ankle vascular index (CAVI).
Pulmonary function was measured with a portable Vitalograph, Copd-6 m: forced expiratory volume in 1 s (FEV1) and forced expiratory volume in 6 s (FEV6)
Forest walking group significantly improved CAVI (p < 0.01), FEV1 (p < 0.01) and FEV6 (p < 0.01).
No significant change was observed in the city-walking group.
There were significant differences in changes of CAVI (p < 0.01), FEV1 (p = 0.02), and FEV6 (p = 0.04), between the groups.
Both systolic and diastolic blood pressure decreased significantly in forest walking group but did not changed in city walking group.
No significant side effects were reported.
Sonntag-Öström et al. [5] 2015
Scandinavian Journal of Forest Research
RCT Sweden N = 99
Intervention group mean age: 44.6 (9.1)
Control group mean age: 44.5 (8.1)
Female (n = 85) and male (n = 14) patients diagnosed with exhaustion disorder (ED)
N = 51
Forest rehabilitation group with subsequent cognitive behavioral rehabilitation (CBR) for all participants
Twice a week for 11 weeks (22 visit in total)
Each time 4 h
Follow up at 3 months
and at the end of the CBR (1 year) in both groups
N = 48
Waiting list group with subsequent CBR.
Burnout level were measures with the Shirom Melamed Burnout Questionnaire (SMBQ),
Stress with the Perceived Stress Questionnaire (PSQ),
Fatigue with the Checklist Individual Strength questionnaire (CIS),
Self-esteem with the Self-Concept Questionnaire (SCQ),
Anxiety and depression with the Hospital Anxiety and Depression Scale (HAD-S),
Mental state was evaluated with the questionnaire asked about the participant’s perceived tenseness (tense/relaxed), fatigue (exhausted/alert), mood (sad/happy), irritability (irritated/harmonious), restlessness (restless/ peaceful) and clear-headedness,
Attention capacity was tested using the Necker Cube Pattern Control task (NCPC), Sick leave data
Both groups had enhanced recovery from ED after the 3-month intervention period and at the end of the CBR (1 year).
There were no significant differences between the groups in terms of psychological health measures.
Mental state was improved, but it showed some seasonal differences. A significant effect on attention capacity was found for single forest visits, but there was no effect found for the rehabilitation period as a whole.
The most popular forest environments contained easily accessible, open and bright settings with visible water and/or shelter.
Forest rehabilitation did not enhance the recovery from ED compared to the control group, but the participants’ well-being was improved after single forest visits.
Jia et al. [6] 2016
Biomedical and Environmental Sciences
RCT China N = 18
Forest intervention: Age (67–77)
Control: Age (61–79)
Elderly patients with COPD.
N = 10
Walk 90 min in the morning and 90 min in the afternoon (total 3 h) and stayed at hotel
1 day N = 8
Urban 90 min in the morning and 90 min in the afternoon (total 3 h) and stayed at hotel
Cytokine (IFN-γ, IL-6, IL-8, IL-1β, TNF-α) measured with ELISA kits,
Relative and absolute number of NK cells (CD56+/CD3−), NK-like (CD56+/CD3−), CD8+ T cells (CD3+/CD8+), perforin and granzyme B expression were measured with flow cytometry, Mood status with POMS
There was a significant decrease of perforin (NK cells, NK-like, CD8+ T cells) (p < 0.05) and granzyme B expressions (NK cells, NK-like, CD8+ T cells), accompanied by decreased levels of pro-inflammatory cytokines (IFN-γ, IL-6, IL-8, IL-1β), C-reactive protein (CRP) and stress hormones (cortisol and epinephrine) in the forest group (p < 0.05).
The scores in the negative subscales of POMS decreased after forest bathing trip (p < 0.05.
The forest bathing trip has health effect on elderly patients with COPD by reducing inflammation and stress level.
  1. AGT angiotensinogen, AT angiotensin, BP blood pressure, BDI Beck Depression Inventory, CRP C-reactive protein, CAVI cardio-ankle vascular index, CIS Checklist Individual Strength questionnaire, ET-1 endothelin-1, Hcy homocysteine, Lymphocyte subsets CD3+/CD4+ (T-helper cells), CD3+/CD8+ (T suppressor cells), and CD3−/CD16+/CD56+ (NK cells), CD cluster of differentiation, NK cells natural killer cells, IFN-γ interferon gamma, IL-6 interleukin-6, IL-8 interleukin-8, IL-1β interleukin-1β, TNF-α tumor necrosis factor α, COPD chronic obstructive pulmonary disease, ED exhaustion disorder, FEV forced expiratory volume, HADS Hospital Anxiety and Depression Scale, RCT randomized controlled trials, ROS risk of bias, MDA malondialdehyde, NDI neck disability index, NCPC Necker Cube Pattern Control task, POMS profile and mood state questionnaire, SMBQ Shirom Melamed Burnout Questionnaire, PSQ Perceived stress questionnaire, SCQ Self-Concept Questionnaire, SOD Superoxide dismutase