Meta-review highlights the need for high-quality research to strengthen the evidence of nature’s impact on mental health and well-being This meta-review synthesized findings from existing literature reviews to provide a more comprehensive understanding of the impact of nature on the mental health and well-being of children and adolescents. The meta-review also incorporated recently published studies that were not included in existing reviews. The meta-review investigated four central questions: (1) How is nature defined in existing literature? (2) What types of nature interventions have been examined? (3) What mental health and well-being outcomes have been assessed? and (4) What does the evidence indicate concerning the impact of nature on the mental health and well-being of children and adolescents?
A search of three academic databases was conducted to identify studies that examined the influence of nature on the mental health and well-being of children and adolescents. Only studies published in English between 2010 and 2022 were considered for inclusion in the meta-review. Both primary studies (original observational or experimental studies) and literature reviews were included in the search. The meta-review focused on studies with children and/or adolescents up to the age of 18; however, studies with participants up to the age of 25 years were included if the mean participant age was below 18 years. Additionally, studies that included adults were also eligible for inclusion if a separate analysis was conducted for participants under 18 years of age. In the search, nature was broadly defined to encompass a range of nature engagements, such as exposure to surrounding green spaces and participation in nature-based interventions. Studies that included any measure of mental health or well-being, including developmental, cognitive, and behavioral outcomes, were considered. A total of 162 studies met these criteria; the quality of these studies was then assessed to identify the highest quality studies for inclusion in the meta-review. This process resulted in the selection of 23 studies, including 16 systematic literature reviews, two scoping literature reviews, and five primary studies. The five primary studies were all cohort studies that were published after the date of the last identified review. The reviews included a total of 441 primary studies, the far majority of which were conducted in high-income countries. The studies were both observational (e.g., studies that examined the relationship between greenspace and mental health) and experimental (e.g., studies that tested the impact of a nature intervention). One review focused on children and adolescents with a diagnosed mental health condition; the others examined non-clinical general populations. Findings were synthesized across studies with descriptive content analysis.
The studies’ definitions of ‘nature’ were characterized along a continuum of three main categories: (1) <em>human-designed environments with natural elements</em>, such as playgrounds with trees; (2) <em>human-designed natural environments</em>, such as gardens; and (3) <em>natural environments</em>, such as woodlands. However, some studies did not provide a precise definition of nature and instead used broader terms, like greenspace. The studies examined access, exposure, or engagement with nature. <em>Access studies</em> commonly examined access to surrounding nature near the home, <em>exposure studies</em> focused on the effects of nature or greenspace views, and <em>engagement studies</em> examined outdoor education or nature-based interventions. The range of mental health and well-being outcomes found by the meta-review were also categorized along a continuum that ranged from ‘disorder’ to 'well-being.' The continuum consists of five categories: (1) <em>disorder</em> (e.g., anxiety, depression, ADHD); (2) <em>difficulties/problems</em> (e.g., hyperactivity, attention problems, conduct problems, emotional/behavioral problems); (3) <em>development</em> (e.g., cognitive development, socio-emotional functioning, working memory); (4) <em>competencies</em> (e.g., social competence, academic performance, self-regulation, social skills); and (5) <em>well-being</em> (e.g., psychological, emotional, and mental well-being, resilience, happiness). Mental health and well-being symptoms or behaviors and cognitive and developmental outcomes were most frequently examined; fewer studies assessed mental disorders. Studies with younger children generally focused more on developmental and cognitive outcomes, and studies of adolescents tended to examine mental health outcomes.
Overall, the evidence suggests that nature benefits mental health and well-being, with most studies reporting that nature supported positive effects. Some studies were inconclusive, but none showed negative impacts. Findings focused specifically on children revealed that four literature reviews reported a beneficial effect of nature on children’s mental health; however, findings were mixed among the three primary studies involving children. Among the four reviews that assessed adolescents’ mental health or well-being, results mainly pointed to a beneficial effect, although some uncertain findings were also reported. Ten reviews focused on both child and adolescent populations, with their findings again supporting nature’s beneficial effects on mental health and well-being. Further, primary studies involving both children and adolescents reported beneficial effects on mental well-being, as well as some evidence suggesting potential benefits for childhood development and academic outcomes (although these findings did not reach statistical significance).
Although the meta-review synthesized a broad research base that largely supports the beneficial effects of nature, the authors concluded that “to date, it is difficult to judge the strength of the evidence for nature interventions for mental health and well-being in children and adolescents.” However, the authors indicate that for healthy (non-clinical) child and adolescent populations, “there is sufficient indication of benefit to motivate more high-quality research into the relationship between nature and mental health and well-being (including cognitive and academic outcomes).” Further research is needed to clarify if nature offers similar benefits for children and adolescents with clinical mental health diagnoses. The review also identified several other gaps in the existing body of research. Continued research is needed to improve understanding of how sociodemographic factors, such as socioeconomic status and race/ethnicity, influence nature’s impacts on mental health and well-being. Additionally, the evidence base is nearly exclusively based on studies conducted in high-income countries; research must therefore turn attention to children and adolescents from low- and middle-income countries. Finally, research is also needed to examine “the type, quality and dose of nature” necessary to “reap its beneficial effects.” The meta-review offers two frameworks to guide researchers in operationalizing ‘nature’ and ‘nature interventions.’
The Bottom Line