The relationship between urban greenness and mental health: A national-level study of China.

• Urban-scale greenness and residents' mental health are postiviely associated. • The assocaitions are moderated by urban built and social environments. • Healthy city planning should consider multiple factors in the environments. • Urban-scale greenness creating non-use values serves as a local public good. The relationship between urban greenness and residents' mental health is a critical subject of academic research, but no conclusive findings have been identified yet. Based on a large-scale social survey dataset in China, this study explores the association between urban greenness and residents' mental health and the moderating effect of the built and social environments on the association. The research found that urban greenness is significantly and positively associated with residents' mental health, to varying degrees, in cities with different built and social environments. In cities with medium scale and population density, greenness is found to be more significantly associated with residents' mental health, as it is in cities with a higher level of social fairness. The findings not only lend support to the health promotion model of social ecology, which suggests that mental health is associated with the external built and social environments, but also provides evidence to understand the benefits of urban greenness as a public good. In healthy city-oriented planning practices, multiple factors in the built and social environments should be considered in order to give full play to the health benefits of urban greenness. [ABSTRACT FROM AUTHOR]