October 10 (HealthDay News) -- Adolescent boys with a certain genetic makeup are more likely to have delinquent peers, researchers say.

Being antisocial, using drugs, and criminal behavior is known to be linked to having delinquent peers. And belonging to a delinquent peer group is one of the strongest predictors of criminal behavior.

A study published in the September issue of the Journal of Genetic Psychology looked at the genetic makeup of 1,816 boys in middle and high school.

The researchers found that the boys who had a particular variation -- the 10-repeat allele -- in the dopamine transporter gene (DAT1) were more likely to be affiliated with delinquent peers. However, the gene variation only affected the risk of having delinquent peers in a certain environment.

In boys who were from a high-risk family environment, marked by a disengaged mother and absence of maternal affection, the DAT1 variant was associated with having delinquent peers. But in those who lived in low-risk families (those with high maternal engagement and warmth), the DAT1 variant was not statistically associated with having antisocial peers.

"Our research has confirmed the importance of not only the genome, but also the environment," Kevin M. Beaver, a criminologist at Florida State University, said in a school news release.

Beaver said that he and his colleagues can only hypothesize why the variant just affected the boys from high-risk families.

"Perhaps the 10-repeat allele is triggered by constant stress or the general lack of support, whereas in low-risk households, the variation might remain inactive," he said. "Or it's possible that the 10-repeat allele increases an adolescent boy's attraction to delinquent peers regardless of family type, but parents from low-risk families are simply better able to monitor and control such genetic tendencies."

The 10-repeat allele was not associated with an affinity for antisocial peers among adolescent girls, whether the girls lived in a high-risk or low-risk environment.

SOURCE: Florida State University, news release, Oct. 1, 2008