Content area
Full Text
Objectives. To test the hypothesis that violence among US adolescents spreads like a contagious disease through social networks.
Methods. Participants were a nationally representative sample of 90 118 US students aged 12 to 18 years who were involved in the National Longitudinal Study of Adolescent Health. Violence was assessed by having participants report the number of times in the preceding 12 months they had been involved in a serious physical fight, had hurt someone badly, and had pulled a weapon on someone.
Results. Participants were 48% more likely to have been involved in a serious fight, 183% more likely to have hurt someone badly, and 140% more likely to have pulled a weapon on someone if a friend had engaged in the same behavior.The influence spread up to 4 degrees of separation (i.e., friend of friend of friend of friend) for serious fights, 2 degrees for hurting someone badly, and 3 degrees for pulling a weapon on someone.
Conclusions. Adolescents were more likely to engage in violent behavior if their friends did the same, and contagion of violence extended beyond immediate friends to friends of friends. (Am J Public Health. 2017;107:288-294. doi:10.2105/AJPH. 2016.303550)
Throughout history, contagious diseases and violence have been among the greatest killers of human beings. Although violence and contagious diseases may seem to share little in common, several scholars have proposed that they are similar.1 For example, a 5-year longitudinal study revealed that teenagers who had witnessed gun violence were more than twice as likely as those who had not to commit gun violence themselves.2 The study's lead author, Felton J. Earls of Harvard Medical School, concluded that "based on this study's results, showing the importance ofpersonal contact with violence, the best model for violence may be that of a socially infectious disease. Preventing one violent crime may prevent a downstream cascade of 'infections.'"3 The present research adds to this body of work.
SIMILARITY OF VIOLENCE TO CONTAGIOUS DISEASE
Although imperfect, the analogy that violence is like a contagious disease might shed light on how violence can spread within communities. People exposed to a contagious disease are at increased risk of contracting the disease themselves. Numerous studies have shown that people who are exposed to violence-as observers or victims-are more likely...