Friends' social aggression linked

MONTREAL, Feb. 9 (UPI) -- Physical aggression in children comes from genes and environment, but social aggression has more to do with environmental factors, a Canadian study said.

Researchers at the University of Quebec at Montreal, Laval University in Quebec City, Concordia University in Montreal and the University of Montreal assessed some 400 pairs of 7-year-old twins. Each of sets of twins were asked to list up to three friends in their classroom. Teachers and peers evaluated the twins' and their friends' levels of social and physical aggression.

The study, published in the journal Child Development, found that friends' physical aggression interacts with genetic liability to predict children's own physical aggression -- the genetic disposition to physical aggression is more likely to express itself when children are exposed to physically aggressive friends.

However, no gene-environment interaction was found with respect to children's social aggression. Friends' social aggression seemed to be directly associated with children's own social aggression, independent of children's genetic disposition to this behavior, the researchers said.