Researchers Find Genetic Link to Violence, Delinquency

Three genes could factor heavily into determining why some young men born into underprivileged neighborhoods or families become violent criminals – while their counterparts do not, according to a new report by U.S. researchers.

One gene, MAOA, which played an especially strong role, has been shown in other studies to affect antisocial behavior at disturbingly high rates, the University of North Carolina research team reported. Its findings were published in the August issue of the American Sociological Review.

Sociology professor Guang Guo, who led the study, said people with a certain variation of the MAOA gene – called 2R – were very prone to criminal and delinquent behavior. MAOA regulates several message-carrying chemicals called neurotransmitters that are vital in aggression, emotion and cognition.

"I don't want to say it is a crime gene, but 1 percent of people have it and scored very high in violence and delinquency," Guo told Reuters.

The dopamine transporter 1 (DAT1) gene and the dopamine D2 receptor (DRD2) gene were also associated with delinquent behavior, but only when the boys suffered some other stress like family issues or poor academic performance.

Guo’s team used data from the National Longitudinal Study of Adolescent Health, a U.S. nationally representative sample of about 20,000 adolescents in grades 7 to 12. The study, which only involved boys, interviewed the subjects regularly, including some who gave blood samples.

Based on some of the boys' answers, Guo’s team constructed a “serious delinquency scale,” they wrote.

"Nonviolent delinquency includes stealing amounts larger or smaller than $50, breaking and entering, and selling drugs," they wrote in the August issue of the American Sociological Review.

"Violent delinquency includes serious physical fighting that resulted in injuries needing medical treatment, use of weapons to get something from someone, involvement in physical fighting between groups, shooting or stabbing someone, deliberately damaging property, and pulling a knife or gun on someone."