Just like the flu, violence can be contagious, according to researchers from Ohio State University.
Published in the American Journal of Public Health, the study found that teens are 48 percent more likely to get involved in a serious fight, 183 percent more likely to hurt someone badly and 140 percent more likely to have pulled a weapon on someone if a friend had engaged in the same behavior.
Co-author Brad Bushman, a professor of communication science and researcher on aggression and violence, said the study is one of the first to look at just how far a friend’s influence goes.
“Other studies have shown we are influenced by our friends, but no other study has looked at whether, or how far the behavior spreads,” he said to CNN.
Robert Bond, an expert on social networks, partnered with Bushman to test the hypothesis that violence spreads like disease. The participants’ violent behavior was assessed through an interview that asked them to report the number of times in the last 12 months that they were involved in a serious physical fight, hurt someone enough to need bandages or medical care, or pulled a weapon on someone.
The authors reviewed data taken between 1994 and 1995. The data showed that 32 percent of participants had been involved in at least one serious fight, 14 percent had hurt someone enough for medical attention and more than 2 percent had pulled a weapon on someone.
“We found that for serious fights, a participant was 48 percent more likely to engage in a serious fight if their friend had, and it spread four degrees to their friend’s friend’s friend’s friend,” explained Bushman. “And they were 40 percent more likely to pull a weapon on someone if their friend had – and that spread three degrees to their friend’s friend’s friend. And they were 183 percent more likely to hurt someone badly enough to need medical attention, and that spread two degrees to their friend’s friend.”
The data pulled from 1996 showed that 20 percent of participants had been in at least one serious fight, six percent had hurt someone enough for medical attention and almost three percent had pulled a weapon on someone. The researchers analyzed the three items separately instead of combining them into one measure of violence because the numbers reported were so different.
When the researchers specifically looked at teen boys, they found that for each additional friend who had seriously hurt someone, the likelihood of a participant doing the same increased by 82 percent. The participants’ likelihood of seriously hurting someone increased by 78 percent when their siblings had done so.
The study didn’t control for demographic factors and relied on the honesty of the teens who were interviewed. The authors also said they could not resolve an issue of selection versus contagion – i.e., whether a violent friend causes violence in someone.
Though the study raised some questions by experts, its data is still valuable. Cathryn Galanter, a child and adolescent psychiatrist, said the study has important public health implications.
“I think it’s evidence for something that we see clinically and we also see in our daily life – that often times there is a contagion effect to violence in that for adolescents, having an association with somebody violent or being in a community where there’s a lot of violence puts you at risk [for committing violence],” she said.