A new study, "Delinquent Peer Group Formation: Evidence of a Gene X Environment Correlation," by Florida State University researchers published in the September 2008 issue of the Journal of Genetic Psychology, finds that a gene variant of the dopamine transporter (DAT1) gene puts some males at risk of deliquency. As the press release describing the study explains:
Criminological research has long linked antisocial, drug-using and criminal behavior to delinquent peers—in fact, belonging to such a peer group is one of the strongest correlates to both youthful and adult crime. But the study led by Beaver is the first to establish a statistically significant association between an affinity for antisocial peer groups and a particular variation (called the 10-repeat allele) of the dopamine transporter gene (DAT1).
However, the study's analysis of family, peer and DNA data from 1,816 boys in middle and high school found that the association between DAT1 and delinquent peer affiliation applied primarily for those who had both the 10-repeat allele and a high-risk family environment (one marked by a disengaged mother and an absence of maternal affection).
In contrast, adolescent males with the very same gene variation who lived in low-risk families (those with high levels of maternal engagement and warmth) showed no statistically relevant affinity for antisocial friends.
"Our research has confirmed the importance of not only the genome but also the environment," [FSU criminologist Kevin] Beaver said. "With a sample comprised of 1,816 individuals, more than usual for a genetic study, we were able to document a clear link between DAT1 and delinquent peers for adolescents raised in high-risk families while finding little or no such link in those from low-risk families. As a result, we now have genuine empirical evidence that the social and family environment in an adolescent's life can either exacerbate or blunt genetic effects."
A 2007 Michigan State University study of twins also found a link between the DAT1 variant and "adolescent-onset or adolescent-limited antisocial behavior." In 2002, Wisconsin University researchers reported that young males with a variant of the gene that encodes the brain enzyme monoamine oxidase A (MAOA) have a propensity toward criminality.
So are criminals born or made? The answer from these studies appears to be that they are "made" by the interaction of certain genetic vulnerabilities with bad experiences.
With the rapid spread of genotyping, the question arises: should infants be tested for these gene variants? Such testing could alert parents and enable them take steps to shield their kids from situations that might exacerbate their genetic vulnerabilities. Or would such testing just result in some kids being treated as "bad seeds"?