In what is likely the first long-term study of its kind, NIEHS grantees from the University of Southern California (USC) reported strong evidence that neighborhood greenspaces are beneficial in reducing aggressive behaviors in adolescents who live in urban areas.
The study, published in the July issue of the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP) was a collaboration among researchers in the USC Departments of Preventive Medicine and Psychology.
“Our collaborative work belongs to an emerging area of environmental neurosciences, where the concept and methods in environmental health sciences are brought into social neurosciences to better understand how physical environments affect aggressive behaviors in the community,” said Jiu-Chiuan Chen, M.D., Sc.D., senior author of the JAACAP study.
The paper was highlighted in an editorial in the same issue, written by Peter Jensen, M.D., from the REACH Institute in New York and the Psychiatric Research Institute at the University of Arkansas.
Small changes add up
The scientists examined a multiethnic group of 1,287 twins and triplets, aged nine to eighteen years, living in Southern California. Parents regularly assessed and reported aggressive behavior, both physical and verbal, between 2000 and 2012.
Researchers compared adolescent aggression to satellite data from the Global Agricultural Monitoring Project to measure levels of greenery in participants’ neighborhoods.
“Although the demonstrated ‘effects’ of greenspace were relatively small and did not explain the bulk of child or adolescent aggressive behavior, the researchers rightly point out that these small effects spread out over an entire population could result in 12 percent decreases in the numbers of youth above clinically significant thresholds for aggressive disorders,” Jensen wrote in his editorial.
Vegetation linked to aggression reduction
Researchers found that exposure to greenspace, both short-term, one to six months, and long-term, one to three years, within 1,000 meters of the home were associated with reduced adolescent aggressive behaviors.
The authors reported that the behavioral benefit to increasing vegetation exposure was equivalent to approximately two to two and a half years of maturation, because reported aggressions decreased with age. Interestingly, factors such as age, gender, race or ethnicity, household socioeconomic status, neighborhood quality, maternal smoking during pregnancy, and maternal depression did not modify these associations.
“One of the biggest strengths of this unique project is the effort put into ruling out confounding factors,” said Liam O’Fallon, program analyst in the NIEHS Population Health Branch.
Insights for clinicians and urban planners
Jensen stressed the importance of the study to clinicians treating adolescents. “We must ensure that current and future generations of child and adolescent psychiatrists know how to evaluate and intervene with critical factors in children’s environments and how to restore the essential elements of health in their crucial developmental contexts,” he wrote.
The study also provides important insights for urban planners. “If substantiated in other studies, these results should motivate community-based interventions to determine the effectiveness of greenspace as a preemptive strategy to reduce aggressive behavior in urban environments,” the authors wrote.
“This study is a good step in providing information that could be used by decision-makers to promote public health in urban planning,” O’Fallon emphasized. “But as the authors state, there needs to be additional research to test these findings in other places. In the meantime, these results add to the literature about the healthful benefits of being in nature and exposure to greenspace.”
Jensen PS. 2016. It takes a (green) village…. J Am Acad Child Adolesc Psychiatry. 55(7):540–541.
Younan D, Tuvblad C, Li L, Wu J, Lurmann F, Franklin M, Berhane K, McConnell R, Wu AH, Baker LA, Chen JC. 2016. Environmental determinants of aggression in adolescents: role of urban neighborhood greenspace. J Am Acad Child Adolesc Psychiatry 55(7):591–601.
(Tara Ann Cartwright, Ph.D., is a former postdoctoral fellow in the NIEHS Intracellular Regulation Group).