As people develop, genetic factors may strongly influence who they choose as their friends, a U.S. study finds.
The study, which was published in the August issue of the journal Archives of General Psychiatry, tracked more than 1,800 male twin pairs from mid-childhood to early adulthood between 1998 and 2004.
"As we grow and move out of our home environment, our genetically influenced temperament becomes more and more important in influencing the kinds of friends we like to hang out with," lead author Dr. Kenneth S. Kendler, professor of psychiatry and human genetics at Virginia Commonwealth University's School of Medicine, in Richmond, said in a prepared statement.
This kind of research may help improve understanding of who is at risk for future substance abuse or other "externalizing" behaviors such as conduct and antisocial personality disorder, the researchers said.
"The study shows how genetic and family environmental factors influence the ways in which we create our own social environment as we grow," Kendler said.
He noted that the "road from genes to externalizing behaviors like drug use and antisocial behaviors is not entirely direct or biological. An important part of this pathway involves our genetics influencing our own social environment, which in turn impacts on our risk for a whole host of deviant behaviors."
The study findings "demonstrate clearly that a complete understanding of the pathway from genes to antisocial behaviors, including drug abuse, has to take into account self-selection into deviant versus benign environments," Kendler said. "The effects of peers in adolescence can be quite powerful, either encouraging or discouraging deviant behaviors. Peers also provide access to substances of abuse."