Chapel Hill, NC-- A new study exploring the link between adolescent delinquency and genetics has identified three genes that appear to play a role in whether a child becomes involved in serious and violent crime.
The impact those genes have appears to be triggered or suppressed by social influences such as family, friends and school, according to researchers from the University of North Carolina at Chapel Hill.
The findings were published in the August issue of the American Sociological Review.
The study is one of the first to link molecular genetic variants to adolescent delinquency.
It also sheds light on why some individuals become serious and violent delinquents while others with a similar genetic makeup do not.
Previous behavioral studies examining gene-environment interactions have tended to look at the relationship of genes to a single factor such as child abuse or stress.
The UNC researchers systematically examined several layers of social context, such as family dynamics, peer relations and school-related variables.
"While genetics appear to influence delinquency, social influences such as family, friends and school seem to impact the expression of certain genetic variants," said Guang Guo, Ph.D., the study's lead author and a professor of sociology in the UNC College of Arts and Sciences.
"Positive social influences appear to reduce the delinquency-increasing effect of a genetic variant, whereas the effect of these genetic variants is amplified in the absence of social controls," said Guo, who is also a faculty fellow at the UNC Carolina Population Center and the Carolina Center for Genomic Sciences.
"Our research confirms that genetic effects are not deterministic," Guo said. "Gene expression may depend heavily on the environment."
The three genes were the monoamine oxidase A (MAOA) gene; the dopamine transporter 1 (DAT1) gene; and the dopamine D2 receptor (DRD2) gene.
MAOA regulates several brain neurotransmitters important in behavioral motivation, aggression, emotion and cognition. Among the findings, the research suggests the propensity for serious delinquency increased dramatically among adolescent boys who both repeated a grade and have a 2R allele version of the MAOA gene.
The study also indicates a link between the DRD2 gene and having daily family meals. Daily meals with one or two parents are a powerful moderator for the effect of the DRD2 gene, Guo said.
"Most delinquent and violent behaviors are considered complex," Guo said. "Understanding these behaviors requires understanding both their socioeconomic-cultural components and their genetic components." According to Guo, the correlation of social and genetic effects on delinquency suggests the need for the social sciences to incorporate genetic evidence in this area of study.
The findings also raise important questions for public policy, he said.
For this study researchers examined a sample of approximately 1,100 males in grades 7 through 12 whose DNA and social-control measures were available through the National Longitudinal Study of Adolescent Health.
The research was supported in part by grants from the National Institutes of Health and the National Science Foundation.
The entire study can be read at: http://www.asanet.org/galleries/defaultfile/Aug08ASRFeature.pdf.
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