FOR IMMEDIATE RELEASE
1 August 2008

CONTACT: Julie Hayworth-Perman
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Study Links Secondhand Smoke and Lead Exposure to Conduct Disorder in Children

Report in Environmental Health Perspectives finds recurrent disruptive behavior more likely for children exposed to toxicants

[RESEARCH TRIANGLE PARK, NC] A national study of 3,091 U.S. children has linked an increased risk for conduct disorder (CD) to postnatal lead exposure and both pre- and postnatal exposure to secondhand smoke. The findings, reported in the July 2008 edition of the peer-reviewed journal Environmental Health Perspectives (EHP), confirm the results of smaller studies associating CD to these toxicants.

The current study is the first to use Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria to assess CD and the exposures of interest in a nationally representative sample of U.S. children. Using data from the National Health and Nutrition Examination Survey (NHANES) 2001-2004, a national cross-sectional sample of the non-institutionalized U.S. population, authors examined the association of prenatal tobacco smoke, postnatal tobacco smoke, and postnatal lead exposure with CD in children 8-15 years of age. Potential prenatal tobacco smoke exposure was estimated on the basis of parental reports of smoking during pregnancy, and postnatal tobacco smoke exposure was assessed by measuring serum cotinine (the major metabolite of nicotine that indicates levels of nicotine intake). Lead exposure was assessed using current blood lead concentration. Parents completed the Diagnostic Interview Schedule for Children to determine whether their children met DSM-IV criteria for CD.

"Despite dramatic reductions in children's exposures to tobacco smoke and environmental lead, these results suggest that millions of contemporary children may be exposed to levels of these intoxicants sufficient to increase the risk for persistent, disruptive, and even violent behavior problems," said Joseph Braun, lead author for the study.

Overall, 2.06 percent of children met the DSM-IV criteria for CD in the past year, equivalent to 560,000 U.S. children 8-15 years of age. After adjustment, prenatal tobacco smoke exposure was associated with increased odds for CD. The research team determined that children exposed prenatally to secondhand smoke were threefold more likely to meet CD diagnostic criteria than those not exposed. Youngsters exposed postnatally to the highest levels of secondhand smoke were 9.15 times more likely to exhibit CD symptoms than those exposed to the lowest levels.

Children with blood lead levels higher than 1.5 µg/dL were 8.64 times more likely to have met CD diagnostic criteria in the past year than children with levels lower than 0.7 µg/dL.

According to the American Psychiatric Association, CD is characterized by persistent behavioral patterns that violate social rules and the rights of individuals. Children with CD display aggression toward people and animals, intentionally destroy others' property, and chronically steal or deceive. Children with CD are at increased risk for drug and alcohol abuse, antisocial personality disorder, and anxiety-related disorder (Goldstein et al. 2006; Gunter at al. 2006).

"Childhood exposure to secondhand smoke and lead is widely recognized as a cause of negative biological outcomes, but this study highlights the impact these neurotoxicants may have on behavioral development," said EHP editor-in-chief Hugh A. Tilson, PhD. "The findings of this study impact not only parents and caregivers of children with CD but the public at large as well through rising costs for appropriate care and services."

The lead author of the study was Joseph M. Braun of the University of North Carolina at Chapel Hill Department of Epidemiology. Other authors included Tanya E. Froehlich, Julie L. Daniels, Kim N. Dietrich, Richard Hornung, Peggy Auinger, and Bruce P. Lanphear. The article is available free of charge at http://www.ehponline.org/members/2008/11177/11177.html.

EHP is published by the National Institute of Environmental Health Sciences (NIEHS), part of the U.S. Department of Health and Human Services. EHP is an Open Access journal. More information is available online at http://www.ehponline.org/. Brogan & Partners Convergence Marketing handles marketing and public relations for the publication and is responsible for creation and distribution of this press release.