WASHINGTON -- The causes of youth gun violence are complex and while focusing on just a single variable will probably not prevent shootings, understanding and preventing youth violence should be a national priority, according to a comprehensive review published by the American Psychological Association.

"Rampage school shootings threaten our sense of social order, while inner-city street shootings signify entrenched disruptions of social trust. In either situation, there is an urgent need to understand what went wrong. This article explores the complex causes of gun violence among vulnerable youths in these two distinct, but uniformly tragic scenarios," said lead author Brad Bushman, PhD, of The Ohio State University. The article appears in APA's flagship journal American Psychologist.

The article summarizes and updates a report the authors made in 2013 to the National Science Foundation. Bushman and co-author Katherine Newman, PhD, of the University of Massachusetts, Amherst, enlisted 10 other experts to help write an advisory report on what is known and still needs to be discovered about youth violence.

School rampage shootings and street shootings by youth differ in dramatic ways: They are committed by different types of youth for different reasons, and often have very different risk factors, according to the review.

Nearly all school shooters are white, rural or suburban, and middle class. They usually have multiple weapons, including semi-automatic or automatic rifles, purchased legally and often obtained from family members. School shooters also want everyone to know who they are and design their killing sprees as a grand finale, often committing suicide in the end.

In contrast, street shooters tend to be black, poor and live in the inner city. They often have lengthy arrest records and use handguns that they obtained illegally. They don't want people to know what they did and rarely commit suicide.

Despite all the differences between street shooters and school shooters, many of the causes of their actions are not that different, according to the article.

"The causes of gun violence in youth are complex. There are usually multiple factors acting together no matter what kind of shooting is involved," Bushman said.

Some factors, like social rejection from peers, seem to be more related to school shooters. Other factors, like poverty, appear to play a larger role in street shootings. But many factors, like family influences, personality traits, exposure to media violence and access to guns, play a role in both types of youth gun violence, according to the review.

Because youth violence has so many causes, preventing it also requires a multifaceted approach, said Bushman. Many of the solutions are well-known, if not often implemented, such as strengthening families, minimizing violent media effects, reducing youth access to guns and improving school climates.

The review also noted that new technologies make it possible to mine large quantities of online data to help predict potential youth violence, citing as one example the Chicago Police Department using social media (e.g., Facebook profiles) to map relationships among the city's most active gang members to identify individuals at highest risk to be involved in a homicide.

"It is possible to sift through Facebook and Twitter posts to determine if individuals are showing signs of violent behavior," said Bushman. "There are concerns about privacy. We have to make sure that when we do this kind of data mining that we only use data that is publicly available."

Whether by law enforcement, schools or even family, the question of monitoring social media to predict violence is still wide open and it may be some time before a consensus emerges as to whether it is effective, according to Mark Dredze, PhD, of Johns Hopkins University, an author on the review.

One of the most effective methods for preventing school shootings is ensuring that information that "something terrible is about to happen" is brought to trusted adults who have knowledge to respond effectively. This involves improving school climate, according to Bushman.

"You want students to trust parents and teachers and feel like they can talk about possible threats they hear about without ruining someone's life," he said. "Zero-tolerance policies for speech are not helpful, though weapon possession should never be tolerated. Many kids won't report threats they hear if they know a fellow student could be expelled for what could be an idle or non-serious comment."

Both school rampage shootings and everyday street violence need more attention from lawmakers and the public than they currently receive, said Bushman. "We can't begin to solve the problem of youth gun violence if we don't make the issue a major national priority."