Green space and serious psychological distress among adults and teens: A population-based study in California

There has been mounting evidence for the beneficial effect of green space on mental health among adults, but studies on the same topics are lacking for teens in the US. This study aimed to fill in this research gap by utilizing data from California Health Interview Survey (CHIS) 2011-2014. A total of 81,102 households (composed of 4538 teens and 81,102 adults) were retained for main analyses. Surrounding greenness was assessed by the Normalized Difference Vegetation Index (NDVI) within varying buffers of home residence. Survey logistic regressions accounted for sampling weights and design were conducted to examine the effects of greenness on serious psychological distress (SPD), adjusted for major socio-demographic factors, neighborhood socioeconomic status (SES) and co-respondent's psychological distress level within the same household. An inter-quartile increment of NDVI in 350 m buffer predicted decreased odds of SPDs by 36% in teens (OR = 0.64, 95% CI = [0.46, 0.91]). Mediation analyses revealed that this association remained almost unchanged even after adjusting for social cohesion. The NDVI-SPD association of adults was found to be significant only in the older group (OR = 0.81, 95% CI = [0.68, 0.95]). This study is one of the first population-based US studies extending the epidemiological evidence for benefits of green space on mental health from adults to teens.