More green space may improve children’s mental health

An increase in green space may improve children’s mental health, according to results of a cohort study published in JAMA Network Open.

“Urban environmental stressors, including artificial light, air pollution and noise, are ubiquitous in areas of high population density, and there is a growing body of research linking these aspects of the urban landscape to mental health,” Meredith Franklin, PhD, of the department of preventive medicine at the University of Southern California Keck School of Medicine, and colleagues wrote. “Combined with home and neighborhood factors, including exposure to secondhand smoke, family stress, crowding and low household income, these stressors may affect children’s health through key regulatory systems in the body, such as cortisol levels. Increased psychosocial stress responses occurring in critical stages of childhood development can have measurable and lasting health effects.”

Results of prior studies demonstrated the potential role of green space in offsetting these stressors. Specifically, residents in neighborhoods with more greenery appeared to experience less stress and improvement in perceived mental health, and adolescents appeared to exhibit decreased aggression linked to greater neighborhood green space.

Franklin and colleagues aimed to examine the effects of several environmental factors, including artificial light at night (ALAN), near-roadway air pollution (NRP), noise and green space, on self-reported stress among 2,290 children living in eight densely populated urban communities in southern California. They linked exposures of ALAN according to satellite observations, NRP according to a dispersion model, noise estimated according to the U.S. Traffic Noise Model and green space according to satellite observations of the enhanced vegetation index to the geocoded residence of each participant. Further, they used the four-item Perceived Stress Scale (PSS-4), with higher scores on a scale of zero to 16 indicating greater perceived stress, to assess children’s stress at ages 13 to 14 years and 15 to 16 years.

Results showed significantly higher perceived stress among girls vs. boys according to PSS-4 scores. As age increased, the mean PSS-4 score rose from 5.6 to 6 among girls but decreased among boys from 5 to 4.7. Secondhand smoke exposure in the home was linked to a 0.85 (95% CI, 0.46-1.24) increase in PSS-4 score, according to multivariate mixed-effects models that examined multiple exposures. An interquartile range (IQR) increase in ALAN was linked to a 0.57 (95% CI, 0.05-1.09) unit increase in PSS-4 score, as well as a 0.16 score increase per IQR increase of NRP (95% CI, 0.02-0.3) and a 0.24 score decrease per IQR increase of the enhanced vegetation index (95% CI, 0.45 to 0.04). Individuals living in households that earned less than $48,000 per year exhibited significantly increased stress levels per IQR ALAN increase. The researchers noted that sleep duration partially mediated the links between stress and both ALAN (18%) and enhanced vegetation index (17%).

“The confluence of ALAN, NRP, noise and a lack of green space in neighborhoods of Southern California were found to be significantly associated with increased self-reported psychosocial stress in children,” Franklin and colleagues wrote. “Advocating for increased green space and reduced traffic could serve as useful interventions that may have lasting improvements on child mental health.”