The research by sociologists from the University of North Carolina-Chapel Hill, published in the August issue of the American Sociological Review identifies three genetic predictors of serious and violent delinquency that become more powerful predictors when considered together with social influences, such as family, friends and school processes.
While many behavioral studies of gene–environment interactions typically examine the relationship of a single factor (e.g., child abuse, stress) to genes, this research systematically examined layers of social context simultaneously (i.e., 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, the study's lead author and a professor of sociology and faculty fellow at the University of North Carolina-Chapel Hill's Carolina Population Center and Carolina Center for Genomic 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."
"Our research confirms that genetic effects are not deterministic," Guo said. "Gene expression may depend heavily on the environment."
Guo, is therefore suggesting that genes and environment operate together in determining delinquent behaviour. This leaves little room for the role of free will and casts doubt over whether violent criminals should be blamed for their actions. Nevertheless, the research does challenge reductionist models of human behaviour.
The three genetic polymorphisms that predict delinquency include: (1) the 30-base pair (bp) promoter-region with a variable number tandem repeat (VNTR) in the monoamine oxidase A (MAOA) gene, (2) the 40-bp VNTR in the dopamine transporter 1 (DAT1) gene and (3) the Taq1 polymorphism in the dopamine D2 receptor (DRD2) gene. MAOA regulates several brain neurotransmitters important in behavioral motivation, aggression, emotion and cognition (e.g., serotonin, dopamine, norepinephrine).
Among the findings, the research suggests a conditional interaction between repeating a school grade and the MAOA*2 repeat (2R) allele in adolescent boys. For those who did not have the 2R allele, repeating a grade was significantly correlated with serious delinquency, but for those who had this 2R allele and who repeated a grade, the propensity for serious delinquency increased dramatically.
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.
"Most delinquent and violent behaviors are considered complex," Guo said. "Understanding these behaviors requires understanding both their socioeconomic-cultural components and their genetic components."
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, according to Guo. The implications of these findings also raise important questions for public policy.
Source; EurekAlert (Press Release)
