Nature exposure may reduce psychological health disparities among children from different socioeconomic backgroundsChildren in disadvantaged situations—due to low income, parental education, or minority status—face greater risks of poor mental health and developmental issues, likely because of increased daily stress. In recent years, research has started to investigate whether spending time in nature can have an "equigenic effect" on children's mental health by helping disadvantaged children reach psychological outcomes comparable to those of their more advantaged peers. The equigenesis hypothesis suggests that “physical environments may impact human health and functioning differentially, acting as a leveling force, benefiting disadvantaged populations more and promoting equity in both the physical and psychological domains.” This scoping review employed an exploratory approach to map the existing evidence on the equigenic effects of exposure to nature. The review (1) summarizes the existing literature regarding the equigenic effects of nature exposure on health among both adults and children, and (2) provides a focused analysis of research pertaining specifically to children's mental health and psychological development.
A search of three academic databases was conducted to identify peer-reviewed studies that examined the equigenic effects of nature exposure and green space. Only studies published in English were considered for inclusion. The search identified a broad research base of 123 empirical studies and literature reviews that investigated physical or psychological health outcomes for children and adults. From these initial search results, 24 empirical studies were selected that focused on children (age 0–18) and mental health or psychological development outcomes. The studies’ findings were evaluated for evidence of an equigenic effect. The studies were then categorized by their level of support for the equigenesis hypothesis. Studies were deemed supportive of the hypothesis if they reported at least one statistically significant result indicating that nature exposure provided greater benefit for disadvantaged groups than advantaged groups. The remaining studies were categorized as non-supportive (advantaged groups benefited more), conflicting (the study found both supportive and non-supportive evidence), or non-significant (no statistically significant differences between advantaged and disadvantaged groups).
Out of the 123 studies identified in the literature search, 64 (52%) tested for equigenesis by comparing the effects of nature exposure on the health outcomes of advantaged and disadvantaged groups. The majority of studies that tested for an equigenic effect were focused on the mental health outcomes of adult participants. Of the 123 studies, 30 (24%) examined equigenesis specifically in children, and only 24 (20%) investigated outcomes related to children’s psychological health. Of 64 studies on equigenic effects for adults and children, 58% found that nature exposure supported health equity by benefiting disadvantaged groups more. Twenty percent showed no significant differences between groups, while 16% reported mixed results—sometimes disadvantaged groups benefited more, but advantaged groups sometimes saw greater improvements on other measures.
The 24 studies that examined equigenic outcomes for children’s psychological health were published between 2014 and 2024 and were mostly conducted in the U.S. Socioemotional functioning and cognitive functioning were the most frequently studied outcomes. The studies used a range of measures to quantify nature exposure, with the Normalized Difference Vegetation Index being utilized most frequently. Of these studies, 12 (50%) reported that exposure to nature was linked to greater psychological benefits for children living with disadvantage compared to their more advantaged peers. Specific outcomes identified by the studies revealed that children living with greater disadvantage demonstrated stronger outcomes for reduced anxiety, behavioral difficulties, and psychological and behavioral disorders. They also showed larger improvements in reading and math skills, cognitive functioning, and prosocial and pro-environmental behaviors. Seven studies reported conflicting findings that indicated both supportive and non-supportive evidence for the equigenesis hypothesis. Including these studies, 79% of studies revealed some evidence of equigenesis. None of the reviewed studies reported non-supportive evidence of stronger outcomes for advantaged children. However, five studies reported non-significant findings in which disadvantaged and advantaged children benefited equally. The review discusses nature exposure characteristics that may support equigenic effects, including the quality of green space, frequency of nature exposure, contextual setting (i.e., home or school), and the potential importance of early childhood. The authors also examine mechanisms through which nature exposure may especially benefit children in disadvantaged situations and propose a framework for equigenesis-related effects on psychological health.
Overall findings of the review call attention to a growing body of research that demonstrates support for the equigenic effects of nature exposure on physical and psychological health outcomes for adults and children. Although fewer studies have examined the equigenic potential of nature exposure for children’s psychological health, findings of these studies suggest that nature exposure may help to close the gap between advantaged and disadvantaged children's mental health and psychological development. Methodological inconsistencies between studies, such as variation in defining or measuring nature exposure or disadvantage, may explain some instances of mixed findings. While further research is needed, the authors conclude that “the findings to date imply that nature exposure could be a useful tool in promoting equity in psychological health among children of differing advantage.” Policymakers, urban planners, educators and families are encouraged to incorporate nature-based interventions into children's daily routines to promote equitable access and address disparities in children’s mental health and psychological development.
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