New Research: Greenery in Neighborhoods May Reduce Adolescent Aggressive Behavior

SCEHSC Study Supports Benefits of Neighborhood Greenspace on Southern California Adolescents

A study to be published in the July 2016 issue of the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP) reports that adolescents in urban communities may have less aggressive behaviors if they live in neighborhoods with more greenery, such as parks, golf courses or fields.

Studies have shown that the families we grow up in, the places we work, and the friends we keep (our social environment) play a large role in influencing behavior.  However, not much is known about how one’s outdoor environment – such as the greenery in one’s neighborhood – affects behavior.

The University of Southern California (USC) recently conducted the first longitudinal study to see whether greenery surrounding the home could reduce aggressive behaviors in a group of Southern California adolescents living in urban communities.

The team, part of the Southern California Environmental Health Sciences Center at the Keck School of Medicine of USC and the Department of Psychology at the USC Dana and David Dornsife College of Letters, Arts and Sciences, followed 1,287 adolescents, age nine to 18 years. They assessed the adolescents’ aggressive behaviors every two-to-three years, asking parents if their child physically attacked or threatened others, destroyed things or exhibited other similar behaviors. The researchers then linked the adolescents’ residential locations to satellite data to measure the levels of greenery in their neighborhoods.

The study found that nine to 18 year-olds who lived in places with more greenery had significantly less aggressive behaviors than those living in neighborhoods with less greenery.  Both short-term (one-to-six months) and long-term (one-to-three years) exposure to greenspace within 1,000 meters surrounding residences were associated with reduced aggressive behaviors.  The behavioral benefit of greenspace equated to approximately two to two-and-a-half years of adolescent maturation.

The study also found that factors such as age, gender, race/ethnicity, socioeconomic status, parents’ educational background, occupation, income level or marital status, and whether their mother smoked while pregnant or was depressed, did not affect the findings.

Additionally, these benefits existed for both boys and girls of all ages and races/ethnicities, and across populations with different socioeconomic backgrounds and living in communities with different neighborhood quality.

“Identifying effective measures to reduce aggressive and violent behaviors in adolescents is a pressing issue facing societies worldwide,” said Diana Younan, M.P.H., doctoral candidate at the Keck School of Medicine. “It is important that we target aggressive behaviors early-on. Our study provides new evidence that increasing neighborhood greenery may be an effective alternative intervention strategy for an environmental public health approach that has not been considered yet.”

Based on the study’s findings, USC investigators and their collaborators estimate that increasing greenery levels commonly seen in urban environments could result in a 12 percent decrease in clinical cases of aggressive behavior in California adolescents living in urban areas.  Researchers conclude that these results support the benefits of greenery in decreasing aggressive behaviors for adolescents living in urban communities.

This new knowledge may provide a strong reason for further studies to examine if improving greenery in residential neighborhoods will indeed reduce aggressive behaviors in adolescents.

The article “Environmental Determinants of Aggression in Adolescents: Role of Urban Neighborhood Greenspace” by Diana Younan, Catherine Tuvblad, Lianfa Li, Jun Wu, Fred Lurmann, Meredith Franklin, Kiros Berhane, Rob McConnell, Anna H. Wu, Laura Baker, and Jiu-Chiuan Chen ( appears in the Journal of the American Academy of Child and Adolescent Psychiatry, Volume 55, Issue 7 (July 2016), published by Elsevier.

Keck School of Medicine of USC research finds air pollution may affect the way the brain ages and functions

Effects on brain’s white matter seen in older women who lived in locations with high levels of small particles in ambient air

PRESS: New York Times,, Yahoo Health ,, Mother Jones

LOS ANGELES – Exposure to air pollution has been known to affect respiratory diseases, lung function and cardiac health, but a new study led by Keck School of Medicine of the University of Southern California (USC) researchers shows for the first time that it may also have a negative impact on how the brain’s white matter ages.

The research indicates that older women who lived in geographic locations with higher levels of fine particulate matter in ambient air had significantly smaller white matter volumes across a wide range of brain areas.

Fine particulate matter is smaller than 2.5 micrometers and is known as PM2.5, a form of pollution that easily enters the lungs and possibly the bloodstream. White matter connects brain regions and determines how information is processed in the brain.

“Investigating the impact of air pollution on the human brain is a new area of environmental neurosciences,” said Jiu-­‐Chiuan Chen, M.D., M.P.H., Sc.D., associate professor of preventive medicine at the Keck School of Medicine and lead author of the research. “Our study provides convincing evidence that several parts of the aging brain, especially the white matter, are an important target of neurotoxic effects induced by long-­‐term exposure to fine particles in the air.”

The study found that older women ages 71 -­‐ 89 who had lived in places with greater PM2.5 exposures had significantly smaller volumes of white matter, and that this could not be explained by the geographic region where they lived, their race or ethnic background, socioeconomic status, lifestyle, or medical conditions that may also influence brain volumes.

Click here to see the study abstract.

The researchers performed brain magnetic resonance imaging (MRI) scans of 1,403 women who are part of the Women’s Health Initiative Memory Study (WHIMS), a nationwide study based at Wake Forest Baptist Medical Center in Winston-­‐Salem, N.C. The researchers also used residential histories and air monitoring data to estimate the participants’ exposure to air pollution in the previous six to seven years.

This is the first study to differentiate between white and gray matter while examining the neurotoxic effects of PM2.5 on brain volumes of older people, The USC-­‐led research may be the largest neuroimaging study conducted in community-­‐ dwelling elderly persons to examine the association between long-­‐term PM2.5 exposures and volumes of gray matter and white matter in the brain.

White matter contains nerve fibers and connects brain regions with each other by traveling deep within and passing nerve signals throughout the brain. Gray matter is primarily composed of neuronal cell bodies, dendrites, glial cells, and capillaries. The study did not find impacts from exposure to air pollution in participants’ gray matter.

The WHIMS study began in 1996 at Wake Forest Baptist Medical Center for the purpose of studying how postmenopausal hormone treatment affects cognitive impairment and brain aging.

The research appears in the June 15, 2015 issue of the Annals of Neurology. Co-­‐authors include Xinhui Wang, M.S., and Helena Chui, M.D. of the Keck School of Medicine of USC; John McArdle, Ph.D. of the USC Dornsife College of Letters, Arts and Sciences; Gregory Wellenius, Sc.D. of Brown University; Mark Serre, Ph.D. of the University of North Carolina; Ira Driscoll, Ph.D. of the University of Wisconsin; Ramon Casanova, Ph.D. and Mark Espeland, Ph.D. of Wake Forest Baptist Medical Center; and JoAnn Manson, M.D., Dr. P.H. of Harvard Medical School.

The collaborative study was funded by in part by the National Institutes of Health grant R01AG033078 and by the Rosenblith Award from the Health Effects Institute, an organization jointly funded by the United States Environmental Protection Agency and certain auto and engine manufacturers. The work was also supported by the Southern California Environmental Health Sciences Center (5P30ES007048). The research was also supported by the National Heart, Lung, and Blood Institute, National Institute on Aging, National Institutes of Health, U.S. Department of Health and Human Services through contracts and by Wyeth Pharmaceuticals, Inc, St. Davids, PA, and Wake Forest Baptist Medical Center, which funds the Women’s Health Initiative Program and its memory study.

Article cited: Chen, J.C., Wang, X., Wellenius. G.A., Serre, M.L., Driscoll, I., Casanova, R. McArdle, J.J., Manson, J.E., Chui, H.C., Espeland, M.A.. Ambient Air Pollution and Neurotoxicity on Brain Structure: Evidence from Women’s Health Initiative Memory Study. Annals of Neurology June 15, 2015. doi: 10.1002/ana.24460. [Epub ahead of print]. PMID: 26075655

Press Release by Leslie Ridgeway, Keck Medicine of USC Marketing and Communications

About Keck Medicine of USC

Keck Medicine of USC is the University of Southern California’s medical enterprise, one of only two university-­‐based medical systems in the Los Angeles area. For more information, go to