Table 3.

Characteristics of included studies.

First Author and Year

Sample Size (M/F)

Participant Characteristics

Stand Density (Trees/ha)

DBH (cm)

Canopy Density

Forest Characteristics

Environmental Characteristics

Outcome Measurement

Activity Type

Time of Measure

Study Design

An 2019 [84]

13 (7/6)

Healthy university students Age: 21.8 ± 1.9

3 different forest sites (no control assigned)

Location: 43$°$51′ N, 125$°$18′ E

Temp: 18 °C (10–25 °C) Relative humidity: 45% Wind speed: 3.33 m/s

SBP; DBP; HR

Staying (30 min)

Sep, 2017 (8:30–12:00)

Randomized Cross-over

1667/ha

13.26

0.56

Betula platyphylla

Illuminance: 4617 lx

SBP(/); DBP(/); HR(/)

1867/ha

10.35

0.75

Acer triflorum

Illuminance: 1124 lx

SBP(/); DBP(/); HR(+)

1993/ha

14.39

0.78

Quercus mongolica

Illuminance: 1012 lx

SBP(+/); DBP(+/); HR(+/)

Bach 2021 [85]

10 (6/4)

Healthy university students with no abnormalities in the respiratory or immune system Age: 36.4 ± 6.5

One forest site and urban site (control)

Location: $41°73\prime$ N, 2$°44\prime$ E Altitude: 860–972 m Dominant species: Quercus ilex

Temp: 23.87 ± 0.18 °C Relative humidity: 53.7%

Blood concentration of Alpha-pinene(/); Beta-pinene(/); Alpha-phellandrene(/); Limonene(/); All monoterpene(/)

Walking (120 min)

July, 2018 (10:00–12:00)

Randomized Controlled Trial

10500/ha

6.43

0.95

Bielinis 2019 [27]

21 (12/9)

Healthy university students and non-student volunteers with no mental or physical diseases or metabolic syndromes Age: 23.9 ± 2.7

One forest group (no control)

Location: $53°90\prime$ N, 20$°35\prime$ E Dominant species: Picea abies and Pinus sylvestris

Temp: 25 °C Relative humidity: 46% Wind speed: 6.11 m/s Noise: 38.08 ± 5.19 dB Illuminance: 37755.24 lx

SBP(+); DBP(/); PR(+); MAP(+); POMS(Confusion(+) Fatigue(+/) Anger(+) Anxiety(+) Depression(+) Vigor(/)); PANAS(PA(/) NA(+)); ROS(+); SVS(+)

Staying (60 min)

May, 2018 (15:45–16:15)

Uncontrolled Before and After

1200/ha

NA

NA

Elsadek 2019 [86]

346 (200/164)

Healthy university students with no mental or physical diseases Age: 23.0 ± 4.6

3 different forest sites and urban site(control)

Location: $31°27\prime$ N, $121°46\prime$ E

POMS; STAI; ROS; SVS; PET

Walking (15 min)

May, 2018 (10:00–15:30)

Randomized Crossover

NA

NA

0.13

Urban road (control)

Temp: 31.8 °C Relative humidity: 42.8% Wind speed: 0.66 m/s

POMS(Anxiety(−) Depression(−) Anger(−) Fatigue(−) Confusion(−) Vigor(−)); STAI(−); ROS(−); SVS(−)

0.49

Prunus serrulata

Temp: 31.2 °C Relative humidity: 47.0% Wind speed: 0.23 m/s

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+)); STAI(+); ROS(+); SVS(+)

0.89

Plantanus hispanica

Temp: 29.0 °C Relative humidity: 50.9% Wind speed: 0.15m/s

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+)); STAI(+); ROS(+); SVS(+)

0.94

Metasequoia glyptroboides

Temp: 28.1 °C Relative humidity: 52.9% Wind speed: 0.11 m/s

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+)); STAI(+); ROS(+); SVS(+)

Lee 2020 [87]

16 (5/11)

Housewives, freelancers and office workers Age: 41.6 ± 1.8

One forest site and one outdoor site(control)

Location: $35°83\prime$ N, 128$°76\prime$ E Dominant species: Pinus rigida and Quercus aliena

NA

DEP(+/); ANX(+/); AGG(/); ST-IN-S(+); ST-V-RG-P(+)

Staying (120 min)

May–Aug, 2017

Controlled Before and After

156/ha

27.4

NA

Oishi 2003 [88]

44 (23/21)

Healthy residents including students and workers Age: 24.4 ± 9.9

5 different forest sites and one site outside the forest(control)

Location: 39$°{75}^{\prime }$ N, $141°03\prime$ E

POMS

Staying (10 min)

Jul–Sep, 2001 (8:45–13:10)

Non-Randomized Cross-over

250/ha

23

NA

Pinus densiflora

Temp: 19.67 ± 3.31 °C Relative humidity: 68.9%

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+))

750/ha

34.9

Cyptomeria japonica

Temp: 20.29 ± 3.66 °C Relative humidity: 69.3%

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+))

1700/ha

10.6

Quercus serrata

Temp: 19.91 ± 3.40 °C Relative humidity: 75.8%

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+))

2275/ha

10.4

Pinus densiflora Machilus thunbergii

Temp: 20.17 ± 3.19 °C Relative humidity: 73.3%

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+))

2875/ha

9.5

Pinus densiflora Quercus serrata

Temp: 18.63 ± 3.16 °C Relative humidity: 76.4%

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+))

Saito 2019 [89]

17 (17/-)

healthy male volunteer had no history of cardiovascular disease or mental illness Age: 40.2 ± 6.2

2 different forest sites: managed forest and unmanaged forest(control)

Location: $35°41\prime$ N, 138$°86\prime$ E

Wind speed: m/s

SBP; DBP; MAP; HR; HF; LF/HF; saliva cortisol

Staying (15 min)

July, 2014

Randomized Crossover

1024/ha

19.78

0.62

Mixed forest (Broadleaf trees: 82% Coniferous trees: 18%)

Temp: 24.3 ± 2.8 °C Relative humidity: 73.3% Illuminance: 255.0 ± 97.6 lx

SBP(+); DBP(+); MAP(+); HR(/); HF(+/); LF/HF(+); saliva cortisol(+)

1208/ha

15.75

0.91

Mixed forest (Broadleaf trees: 50% Coniferous trees: 50%)

Temp: 24.2 ± 2.8 °C Relative humidity: 70.0% Illuminance: 119.2 ± 48.5 lx

SBP(+); DBP(+); MAP(+); HR; HF(−/); LF/HF(−); saliva cortisol(+/)

Simkin 2020 [90]

66 (41/59)

City workers aged from 26–65 Age: 43.4 ± 10.7

4 different forest sites (no control assigned)

Picea abies-dominated forests in Finland

ROS; SVS; PANAS

Staying (15 min) and Walking (45 min)

Aug–Oct, 2016 April–June, 2017 (15:00–17:00)

Randomized Crossover

374/ha

35

NA

Location: $60°45\prime$ N, 25$°19\prime$ E (stand age > 120)

Temp: 12.8 ± 4.4 °C Relative humidity: 39–96%

ROS(+); SVS(+); PANAS(+)

424/ha

30

Location: $60°22\prime$ N, 24$°92\prime$ E (stand age: 95)

Temp: 15.8 ± 4.2 °C Relative humidity: 29–100%

ROS(+); SVS(+); PANAS(+)

520/ha

28

Location: $60°33\prime$ N, 25$°18\prime$ E (stand age: 100)

Temp: 15.9 ± 5.8 °C Relative humidity: 39–91%

ROS(+); SVS(+); PANAS(+)

1746/ha

16

Location: $60°39\prime$ N, 25$°18\prime$ E (stand age: 40)

Temp: 15.3 ± 4.8 °C Relative humidity: 27–98%

ROS(+); SVS(+); PANAS(+)

Takayama 2017a [91]

18 (18/-)

Healthy male volunteer without history of cardiovascular disease or mental illness Age: 40.2 ± 6.4

2 different forest sites: managed forest and unmanaged forest(control)

Location: $35°41\prime$ N, 138$°$86′ E

POMS; PANAS; ROS; PRS

Staying (15 min)

July, 2014

Randomized Crossover

1056/ha

23.12

0.62

Larix kaempferi 66%, Cornus controversa 10% Pinus densiflora 7%

Temp: 24.3 ± 7.9 °C Relative humidity: 73 ± 39% Wind velocity: $0.13\mathrm{m}$/s Radiant Heat: 25.5 ± 10.5 °C Illuminance: 255.0 ± 97.6 lx Noise: 41.5 ± 3.8 dB

POMS(Anxiety(+) Depression(/) Anger(/) Fatigue(+/) Confusion(+) Vigor(+)); PANAS(PA(/)NA(+)); ROS(+)

1212/ha

18.54

0.91

Larix kaempferi 66% Cornus controversa 7% Pinus densiflora 7%

Temp: 24.2 ± 7.6 °C Relative humidity: 70 ± 34% Wind velocity: $0.23$m/s Radiant Heat: 25.3 ± 9.8 °C Illuminance: 119.2 ± 48.5 lx Noise: 39.0 ± 3.9 dB

POMS(Anxiety(+) Depression(/) Anger(/) Fatigue(/) Confusion(+) Vigor(+)); PANAS(PA(/)NA(+/)) ROS(/)

Takayama 2017 [92]

15 (11/4)

University students and mid-aged faculties without had no history of cardiovascular disease or mental illness Age: 35.9 ± 8.2

2 different forest sites: thinned forest and unthinned forest(control)

Location: 35°41′ N, 138°86′ E

POMS; PANAS; ROS; PRS

Staying (15 min)

Oct, May, 2013

Randomized Crossover

1056/ha

23.12

0.52

Larix kaempferi 66%, Cornus controversa 10% Pinus densiflora 7%

Temp: 18.6 ± 0.92 °C Relative humidity: 92$\pm 4.6$% Wind velocity: $0.16$m/s Radiant Heat: 18.8$\pm 1.1$ °C Illuminance: 336$\pm$172 lx

POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+/) Confusion(+) Vigor(/)); PANAS(PA(/)NA(/)) ROS(+/)

1200/ha

22.76

0.59

Larix kaempferi 66%, Cornus controversa 10% Pinus densiflora 7%

Temp: 17.1$\pm 2$.52 °C Relative humidity: 38$\pm 20$% Wind velocity: $0.30$ m/s Radiant Heat: 21.8$\pm 2.8$ °C Illuminance: 668$\pm 237$ lx

POMS(Anxiety(+) Depression(+) Anger(/) Fatigue(+) Confusion(+) Vigor(/)); PANAS(PA(/)NA(/)) ROS(+)

Yu [93]

123 (43/85)

Middle-aged and elderly subjects aged 45 to 86 years No disease (n = 69), hypertension (n = 25), diabetes (n = 9), heart disease (n = 8) Age: 60.0 ± 7.4

One forest site (no control)

Location: $24°09\prime$ N, 121$°18\prime$ E Dominant species: Cryptomeria japonica

Temp: 22.6 $\pm 1.4$ °C Relative humidity: 87.4% Wind speed: 0.1 $\pm 0.2$ m/s

PR(+); SBP(+); DBP(+); HF(/); LF/HF(/); POMS(Anxiety(+) Depression(+) Anger(+) Fatigue(+) Confusion(+) Vigor(+)); STAI(+)

Walking (180 min)

July, 2016 (8:30–12:00)

Uncontrolled Before and After

1200/ha

NA

NA

Zhou 2019 [94]

43 (8/35)

University students free from diagnosed cardiovascular, allergic, physical disease, or mental diseases Age: 20.8 ± 0.9

2 different forest sites (no control assigned)

Location: $26°11\prime$ N–$26°55\prime$ N 106$°07\prime$ E–107$°17\prime$ E

Temp: 22.6 $\pm 1.4$ °C Relative humidity: 87.4% Wind speed: 0.1 $\pm 0.2$ m/s

Anti-anxiety scores

walking (60 min)

Dec, 2016

Randomized Cross-over

NA

NA

0.20–0.75

Cinnamomum camphora Quercus fabri Platanus acerifolia

Anti-anxiety scores (financial states(+); exam pressure(+); campus life(/); love affair relationship(+))

0.50–0.75

Cinnamomum camphora Celtis sinensis Catalpa bungei Celtis sinensis

Anti-anxiety scores(financial states(+); exam pressure(+); campus life(+); love affair relationship(/))

AGG 7—questions on aggression, ANX 11—questions on anxiety, DBP—diastolic blood pressure, DEP 11—questions on depression, HBP—high-frequency, HR—heart rate, LF/HF—ratio of low-frequency and high frequency, MAP—mean arterial pressure, PANAS—positive and negative affect schedule, POMS—profile of mood states, PR—pulse rate, PRS—perceived restorativeness scale, ROS—restorative outcomes scale, SBP—systolic blood pressure, STAI—state trait anxiety inventory, ST-V-IN-S—five questions on stress vulnerability-interpersonal sensitivity, ST-V-RG-P—five questions on stress vulnerability-self-regulation problems, SVS—subjective vitality scale, Temp—temperature. +: significant effect on positive health outcome; +/: including both significant and nonsignificant effect on positive health outcome; /: nonsignificant effect; -/: including both significant and nonsignificant effect on negative health outcome -: significant effect on negative outcome.