Summary of Strength of Evidence, Stratified by Nature Exposure (n = 296)
| Nature Exposures . | Study Designs (%) . | Findings . | Strength of Evidencea,b . | |||
|---|---|---|---|---|---|---|
| RCTs . | Exp . | XS . | Long . | |||
| Residential green space (n = 147) | 1 | 3 | 128 | 15 | n = 86 studies found positive (health promoting) associations, n = 50 had mixed or null results including different results across subgroups of interest, n = 11 reported negative associations. Most studies (n = 110) were focused on physical health outcomes, n = 30 studies examined cognitive, behavioral, and mental health outcomes, and n = 7 evaluated academic and learning outcomes. | High (−) |
| School green space (n = 40) | 0 | 4 | 34 | 2 | n = 33 studies found positive associations, n = 4 reported mixed or null results, and n = 3 found negative associations. Most studies (n = 22) focused on physical health outcomes, n = 4 studies examined cognitive, behavioral, and mental health outcomes, and n = 12 evaluated academic and learning outcomes. | Moderate (+) |
| Green space activity (n = 35) | 1 | 6 | 28 | 0 | n = 19 studies found positive associations, n = 16 found mixed/null results, and no negative associations were reported. Most studies (n = 27) focused on physical health outcomes, n = 6 studies examined cognitive, behavioral, and mental health outcomes, and n = 2 evaluated academic and learning outcomes. | Moderate (+) |
| Gardening (n = 12) | 5 | 5 | 2 | 0 | n = 7 studies found positive associations, n = 5 found mixed and null results, and no negative associations were reported. Most studies (n = 9) focused on physical health outcomes, n = 2 studies examined cognitive, behavioral, and mental health outcomes, and n = 1 evaluated academic and learning outcomes. | Moderate (−) |
| Wilderness experience (n = 11) | 0 | 11 | 0 | 0 | All studies (n = 11) reported positive associations, regardless of outcome. Most studies (n = 8) focused on cognitive, behavioral, and mental health outcomes, n = 2 studies examined academic and learning outcomes, and n = 1 evaluated physical health outcomes. | Moderate (−) |
| Classroom intervention (n = 17) | 0 | 16 | 1 | 0 | n = 12 studies found positive associations, n = 5 found mixed and null results, and no negative associations were reported. Most studies (n = 9) focused on cognitive, behavioral, and mental health outcomes, n = 6 studies examined physical health outcomes, and n = 2 evaluated academic and learning outcomes. | Low (+) |
| Greening intervention (n = 9) | 1 | 5 | 3 | 0 | n = 4 studies found positive associations, n = 5 found mixed and null results, and no negative associations were reported. Most studies (n = 5) focused on physical health outcomes, n = 3 studies examined cognitive, behavioral, and mental health outcomes, and n = 1 evaluated academic and learning outcomes. | Low |
| Nature walk (n = 4) | 1 | 3 | 0 | 0 | All n = 4 studies found positive associations. n = 2 studies examined cognitive, behavioral, and mental health outcomes, and n = 2 evaluated academic and learning outcomes. | Low |
| Other (n = 21) | 3 | 5 | 9 | 4 | n = 13 studies found positive associations, n = 7 found mixed/null results, and n = 1 negative association was reported. Most studies (n = 16) focused on physical health outcomes, n = 3 studies examined cognitive, behavioral, and mental health outcomes, and n = 2 evaluated academic and learning outcomes. Physical health benefits included better vision, dietary habits, and gut microbial health. | N/A |
| Nature Exposures . | Study Designs (%) . | Findings . | Strength of Evidencea,b . | |||
|---|---|---|---|---|---|---|
| RCTs . | Exp . | XS . | Long . | |||
| Residential green space (n = 147) | 1 | 3 | 128 | 15 | n = 86 studies found positive (health promoting) associations, n = 50 had mixed or null results including different results across subgroups of interest, n = 11 reported negative associations. Most studies (n = 110) were focused on physical health outcomes, n = 30 studies examined cognitive, behavioral, and mental health outcomes, and n = 7 evaluated academic and learning outcomes. | High (−) |
| School green space (n = 40) | 0 | 4 | 34 | 2 | n = 33 studies found positive associations, n = 4 reported mixed or null results, and n = 3 found negative associations. Most studies (n = 22) focused on physical health outcomes, n = 4 studies examined cognitive, behavioral, and mental health outcomes, and n = 12 evaluated academic and learning outcomes. | Moderate (+) |
| Green space activity (n = 35) | 1 | 6 | 28 | 0 | n = 19 studies found positive associations, n = 16 found mixed/null results, and no negative associations were reported. Most studies (n = 27) focused on physical health outcomes, n = 6 studies examined cognitive, behavioral, and mental health outcomes, and n = 2 evaluated academic and learning outcomes. | Moderate (+) |
| Gardening (n = 12) | 5 | 5 | 2 | 0 | n = 7 studies found positive associations, n = 5 found mixed and null results, and no negative associations were reported. Most studies (n = 9) focused on physical health outcomes, n = 2 studies examined cognitive, behavioral, and mental health outcomes, and n = 1 evaluated academic and learning outcomes. | Moderate (−) |
| Wilderness experience (n = 11) | 0 | 11 | 0 | 0 | All studies (n = 11) reported positive associations, regardless of outcome. Most studies (n = 8) focused on cognitive, behavioral, and mental health outcomes, n = 2 studies examined academic and learning outcomes, and n = 1 evaluated physical health outcomes. | Moderate (−) |
| Classroom intervention (n = 17) | 0 | 16 | 1 | 0 | n = 12 studies found positive associations, n = 5 found mixed and null results, and no negative associations were reported. Most studies (n = 9) focused on cognitive, behavioral, and mental health outcomes, n = 6 studies examined physical health outcomes, and n = 2 evaluated academic and learning outcomes. | Low (+) |
| Greening intervention (n = 9) | 1 | 5 | 3 | 0 | n = 4 studies found positive associations, n = 5 found mixed and null results, and no negative associations were reported. Most studies (n = 5) focused on physical health outcomes, n = 3 studies examined cognitive, behavioral, and mental health outcomes, and n = 1 evaluated academic and learning outcomes. | Low |
| Nature walk (n = 4) | 1 | 3 | 0 | 0 | All n = 4 studies found positive associations. n = 2 studies examined cognitive, behavioral, and mental health outcomes, and n = 2 evaluated academic and learning outcomes. | Low |
| Other (n = 21) | 3 | 5 | 9 | 4 | n = 13 studies found positive associations, n = 7 found mixed/null results, and n = 1 negative association was reported. Most studies (n = 16) focused on physical health outcomes, n = 3 studies examined cognitive, behavioral, and mental health outcomes, and n = 2 evaluated academic and learning outcomes. Physical health benefits included better vision, dietary habits, and gut microbial health. | N/A |
Exp, experimental study; Long, longitudinal study; MVPA, moderate or vigorous physical activity; N/A, not applicable; XS, cross-sectional.
Strength of evidence as rated by author consensus on a 7-point scale: low, low+, moderate−, moderate, moderate+, high−, high (see Methods, Strength of Evidence).
Other category not summarized because of high variability in nature exposures.