Mobility-based greenness exposure is associated with racial inequalities in mental health in the U.S.

This is the authors' abstract. We don't add key points for this paper.

Racial inequalities in mental health represent a substantial and preventable public health burden. Although green spaces have been associated with mental well-being, existing approaches to quantifying greenness exposure rely on static residential measures and do not capture behavioral differences in how individuals access and use green spaces across racial groups. We conducted a nationwide analysis of 2,878 U.S. counties, covering 92.2% of all cities, using mental health data from the CDC PLACES project, demographic data from the American Community Survey, and 466 million park visitation records from the SafeGraph Weekly Patterns dataset. We first quantified racial inequalities in mental health using the Gini index. We then developed a mobility-based, behavior-informed metric of dynamic greenness exposure and fitted linear regression models to estimate its associations with tract-level mental health outcomes, adjusting for demographic, socioeconomic, and residential factors. We find that 93.4% of counties exhibit evidence of racial inequality in mental health, with 47.8% showing high levels of inequality (Gini index ≥0.4). Conventional greenness metrics are not associated with these disparities: neighborhoods with predominantly Black residents and high levels of greenness exhibit a similar or higher prevalence of suboptimal mental health than neighborhoods with predominantly White residents and lower levels of greenness. In contrast, higher levels of interracial green-space visitation are associated with a lower prevalence of suboptimal mental health and smaller disparities between neighborhoods with predominantly Black residents and those with predominantly White residents (P < 0.001). Polarized visitation patterns are associated with differences in park accessibility and the concentration of highly rated parks. Our findings highlight a behavioral dimension of greenness exposure that is associated with mental health inequalities. Incorporating mobility and patterns of green space use may improve the assessment of environmental exposures and help identify behavioral and environmental factors associated with population mental health disparities. People from different racial groups in the United States do not experience the same level of mental health. Green spaces, such as parks, are often linked to better mental health, but most studies only measure how much green space is available near where people live. They do not consider whether people actually visit these places. In this study, we combined nationwide information on mental health, neighborhood characteristics, and millions of park visits to examine how people from different communities use green spaces. We found that simply living near more green space was not consistently related to better mental health. Instead, patterns of park use and shared use of parks across communities were more closely associated with mental health differences. These findings suggest that understanding how people access and use green spaces may improve how researchers study environmental influences on mental health. Future studies are needed to determine whether changes in park access or use can help reduce mental health inequalities. Editorial summary: Han, Xia et al. develop a behavior-based measure of greenness exposure, termed greenness segregation, by integrating nationwide human mobility and neighborhood data across the United States. Greenness segregation is more strongly associated with racial inequalities in mental health than conventional residential greenness measures.