Gun Violence Spreads Through Social Networks Like an Epidemic, Study Shows


A new study shows that the likelihood of being shot increases when a person interacts with someone else who's been shot. Erich Schlegel/Getty Images
A new study shows that the likelihood of being shot increases when a person interacts with someone else who's been shot. Erich Schlegel/Getty Images

In 2016, there were nearly 58,000 incidents of gun violence in the United States. The U.S. ranks high on lists comparing countries' rates of gun deaths, and many of the most deadly recent mass shootings in the States occurred in the last several years. But despite the alarming stats, scientists claim gun violence research is underpublished and underfunded. A new study makes the case for more research by showing that gun violence is a public health issue.

Researchers from Yale and Harvard universities found that gun violence spreads among people through social interactions, like a contagious disease. They examined the pool of people arrested from 2006-2014 in Chicago, a city whose gun violence rates are above the national average. From that population, researchers identified instances of death and injury by gunshot. By linking people who co-offended, or were arrested together for the same crime, the study authors created a social network of 11,123 episodes of gun violence that affected 9,773 people. Think of co-offending as the vehicle for the disease, like sex or sharing needles in other epidemics. The researchers acknowledge that because they used only co-offending as a social tie — without considering other relationships, like friendship or employment — the study is limited.

Based on the social contagion model the researchers created, 63.1 percent of the gun violence incidents in the network were influenced by "infectors" who exposed others to the risk of being shot. So, people are more likely to be shot after associating with a shooting victim, especially when that interaction involves committing an offense. And, in true contagion fashion, gun violence even has an incubation period — on average, the "infected" subjects of gun violence were shot 125 days after their infector was shot.

The authors ruled out homophily, the tendency to hang out with similar people, as an explanation for the close social ties of people affected by gun violence. In other words, these shooting patterns didn't occur because the peers were already alike, but because one person's behavior rubbed off on the other.

It may seem obvious that we influence the behaviors and opinions of people we're close to. But typically, efforts to stem gun violence focus on demographics — like age, sex and neighborhood — which puts disproportionate pressure on disadvantaged minority communities. In the study, a model that combined social contagion and demographics predicted 6.5 percent of gun violence subjects, performing better than the separate social contagion and demographics models. This suggests that law enforcement and health professionals could better predict and prevent shootings by considering both factors.

This isn't the first time people have recognized firearm violence as an epidemic, though. In 2016, the American Medical Association called it a "public health crisis," and prior research has studied how gun violence is spread through social relationships. But as gun-related crimes and the debate over stricter gun laws continue, any scientific step toward better violence prevention is invaluable.



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