Abstract
Background: Rising rates of mental health and substance use are significant contributors to illness and disability among adolescents, highlighting a critical area for support and intervention. Existing evidence suggests the physical environment where young people live may impact their mental health. However, research is seldom longitudinal and rarely accounts for the co-location or mixture of potential environmental influences.
Objective: To assess longitudinal relationships between the physical environment in which young people reside in Aotearoa New Zealand and their mental health outcomes.
Method: This study follows a population cohort of 957,381 young people (aged 10-24 years in 2018) over six years (2013-2018), linking their mental health outcomes (emotional, externalising, substance problems, and self-harm) and individual-level characteristics derived from administrative linked microdata with environmental data represented by the Healthy Location Index. Longitudinal Generalised Estimating Equations and quantile g-computing examined longitudinal relationships between the physical environments where young people reside and their mental health.
Results: We found evidence of longitudinal associations between the mixture of physical environment and young people's mental health for emotional disorders (aORΨ = 1.09 [1.08, 1.10]), substance use (aORΨ = 1.04 [1.02, 1.05]), and self-harm (aORΨ = 1.14 [1.10, 1.17]) (but not externalising conditions (aORΨ = 1.01 [0.99, 1.02])), present even after adjusting for individual-level and socioeconomic characteristics. Modelling emphasised the importance of the mix of the environments and the combined positive influence of natural spaces (bluespace and greenspace) for mental health outcomes.
Importance: This study provides longitudinal evidence of meaningful associations between exposure to the combined built and natural environment and mental health in young people. Specifically, living in predominantly health-constraining environments was associated with increased odds of emotional disorders, while greater access to and the mixture of greenspace and bluespace contributed to better mental health outcomes. Our findings are strengthened by a robust longitudinal nationwide study design and comprehensive adjustment, underscoring the significance of the environmental mix. These results extend current evidence and offer novel insights into how physical environments shape young people's mental health over time.