Violence a spreading contagion among teens.

• Position: YOUR LIFE - Brief article

Adolescents are up to 183% more likely to carry out some acts of violence if one of their friends also has committed the same act, according to a study in the American Journal of Public Health, but the spread of violence does not stop at just friends.

Results suggest the contagion extends by up to four degrees of separation--from one person to a friend, to the friend's friend and two more friends beyond. 'This study shows just how contagious violence can be," says lead author Robert Bond. "Acts of violence can ricochet through a community, traveling through networks of friends."

Participants in the study were 48% more likely to have been in a serious fight, 140% more likely to have pulled a weapon on someone, and 183%...