Natural Environments and Health in Adolescents and Young Adults

Abstract

There is growing recognition that natural environments, including both vegetation (greenness or green space) and surface water (blue space) can influence health by providing spaces for physical activity and social interactions, reducing stress, maintaining cognitive skills, and mitigating harmful environmental exposures such as pollution, noise, and extreme heat. Studies to date are suggestive but somewhat limited in scope still. Few population-based studies have considered outcomes in adolescence or the impact of cumulative exposure to nature on subsequent health. We investigated the associations between childhood and adolescent exposure to objectively-measured natural environments and mental and physical health in the Growing Up Today Study (GUTS), a prospective cohort of adolescents and young adults living in the United States. In Chapter 1, we assessed the cross-sectional associations between greenness, blue space, and depressive symptoms during adolescence. Individuals living in areas with greater greenness exposure were less likely to report depressive symptoms, an association that was robust to adjustment to a wide variety of individual, household, and neighborhood social and economic characteristics. There were no associations between any measure of blue space and depressive symptoms. Chapter 2 considered whether surrounding greenness in childhood was associated with the onset of depressive symptoms in adolescence and early adulthood. Growing up in an area of greater greenness was associated with lower onset of depressive symptoms; the association was suggestively stronger in areas of high population density and among younger-onset cases. We observed no associations between surrounding greenness and prevalent or incident overweight and obesity, assessed in Chapter 3. There was suggestive evidence of effect modification by population density, with inverse associations in areas of high density and positive associations in areas of low density. Taken together, these papers suggest that greater exposure to greenness may be beneficial for adolescent and young adult mental health. Associations between greenness and both depressive symptoms and overweight and obesity varied across population density, pointing toward the need for further research how the associations between greenness and health may differ across socio-environmental contexts.