Nonlinear interactive associations between built environments and adults’ mental health in China using a longitudinal design

We attempted to investigate longitudinal nonlinear and interactive associations between built environments and mental health in China, using data from China Family Panel Studies (CFPS) in 2010 and 2014. We employed the XGBoost model to examine how changes in built environments were related to changes in mental health. We observed longitudinal nonlinear threshold effects of built environments on mental health: participants living in neighborhoods with the increase in neighborhood attractiveness reaching to 4-unit and the increase in the quantity of medical facilities reaching to 10 were more likely to have better mental health. In contrast, a substantial increase (between 8 and 12) in the quantity of early education facilities was negatively associated with mental health. Further, improvement in neighborhood attractiveness and increase in the quantity of medical facilities together strengthened mental health benefits. The implications of these findings include that it is critical to identify the threshold for built environment features to achieve optimal mental health benefits. Besides, it is important to integrate multiple built environment features together to amplify the mental health benefits. Intervention strategies should be tailored to specific geographic contexts to prioritize improving built environment features.