Homophily is a term captured by the proverb, birds of a feather flock together and the homophily hypothesis has been shown to explain how bullying is a peer group phenomenon.
When members in a peer group are involved in bullying, the other members tend to take part. Additionally, students who are involved in bully perpetration tended to come from larger peer groups.
Although there is no single causation factor that will identify a bully, as discussed above, negative peer influence was found to predict involvement in bullying and victimization.
The relationship between alcohol/drug use and bullying is well-documented. In a study of middle through high school students, researchers found that aggressive victims and aggressive non-victims were more likely than their nonaggressive counterparts to use drugs and alcohol and a study of 43,093
U.S. adults found that bullying was significantly correlated with lifetime alcohol and drug use. Thus, involvement in bullying is related to concurrent alcohol/drug use as well as future alcohol/drug use.