Does exposing children to violence in TV shows, movies and video games increase their odds of violent behavior later on?

That question lies at the heart of the ongoing debate over gun control, mental health and the effect of violent media on our society. Mass shootings in Newtown, Conn., and elsewhere have brought renewed attention to the issue of who is responsible when a young adult with no history of violence chooses to open fire on innocent people.

Eager to deflect a storm of negative headlines, some gun rights advocates have pointed a finger at video games, movies and other sources of violent images. A similar debate took place after the 1999 Columbine shootings, but the current national conversation surrounding media violence follows a string of particularly violent shootings, climaxing in the tragedy at Sandy Hook Elementary School in December.

The level of outrage following that incident has provided fodder to those concerned about the long-term effects of violent media on children, particularly as video games become more realistic with advances in technology.

The gun lobby found a sympathetic ear in Sen. Joe Manchin III, D-W.Va., who was quick to blame video games such as “Grand Theft Auto” for glorifying violent crimes. He was joined by several other lawmakers, including Sen. Tom Coburn, R-Okla., and Rep. Marsha Blackburn, R-Tenn. President Barack Obama in January called for the Centers for Disease Control and Prevention to invest $10 million in studying the effect of violent video games and movies, among other areas, highlighting the broad public concern over the issue.

But proving a correlation between exposure to violent media images and actual violence is a difficult task at best, especially at a time when children are constantly exposed to violent images on the news and via the Internet.

The American Academy of Pediatrics issued a policy statement on the issue in 2009, arguing that extensive research shows that exposure to media violence can result in aggressive behavior in children. In one study, 98 percent of the pediatricians surveyed believed violent images affect children’s aggression.

The entertainment and video game industries, however, emphasize other studies that find no connection between exposure to violent images and actual violence, and researchers have come to widely differing conclusions depending on their subjects and methodologies.

Critics also note that violent crime in the United States has dropped significantly over the past 20 years, even as media exposure has risen exponentially.

“There has been an assertion made … that our culture is more violent, that there is more violence in our daily lives. And that just simply is not true,” said Simon Rosenberg, president of the Washington think tank NDN, which has accepted funding from the video game industry.

“What we know is that during a time of exploding media exposure, we’ve seen a precipitous decline in violent crime,” Rosenberg said, adding that “it’s very hard to draw any statistical correlation” between exposure to violent media and violent behavior.

Taken as a whole, the only consensus among researchers on the long-term effect of violent media on children appears to be that there is no consensus. Even supporters of limits on violent content admit as much.

Still, Senate Commerce, Science and Transportation Chairman Jay Rockefeller, D-W.Va., has argued for years that exposure to violent media negatively affects young people. He pushed for legislation seven years ago that would have limited violence on broadcast and cable television, but with little success. Subsequent court decisions have made such legislation an even more difficult prospect in the interim.

Rockefeller recently reintroduced a bill that would direct the National Academy of Sciences to take a fresh look at the research in the field, in hopes of finding a more conclusive link between exposure to violent media and violence. He unsuccessfully sought unanimous consent to pass the bill at the end of the last Congress and is waiting for the right moment to attempt another consent request. His staff also hasn’t ruled out moving the bill through committee in regular order.

Supporters of the legislation acknowledge that, even if it passes, it would be just the first step toward enacting limits on violent content. Only definitive evidence linking exposure to violent images and actual violence is likely to sway the Supreme Court, which last weighed in on the issue in 2011.

The broadcast and cable industries have teamed up to promote the tools they offer to help parents screen out violent and sexually explicit content, including the TV and movie ratings systems and the v-chip. The video game industry has not joined that campaign, choosing to tout its own options for parental control. Rockefeller dismisses those attempts at self-regulation.

“I have never believed that voluntary parental controls are sufficient or effective in protecting our children from exposure to violent content,” Rockefeller told CQ Roll Call in an email. “The entertainment industry needs to face the real problem, which is often the unconscionable levels of violence and explicit content in the products they sell.”

Rosenberg pointed out that playing video games has become common behavior for children, unaccompanied by any resulting spike in later violence. Rockefeller’s Republican counterpart on the Commerce Committee is also less convinced about the dangers of media violence.

“Like many parents, of course I am concerned about the types of media children are exposed to,” said ranking member John Thune, R-S.D. “But we have to be careful about drawing conclusions prematurely in response to horrible tragedies. There are many factors that lead to real-world violence, including mental-health issues, and we should look at this important societal issue in a holistic fashion.”

With the combined lobbying might of the video game, movie and TV industries against them, Rockefeller and his supporters face an uphill climb in his effort to police the airwaves. Their best bet is that new research proves a relationship between long-term exposure to violent media and increased violence in children.

Such research would likely take years, and even then, there is no guarantee it would sway the Supreme Court. Rockefeller and his supporters are aware they are still at the beginning of a lengthy campaign, one that will likely last beyond when he leaves office at the end of the 113th Congress. In the interim, that leaves parents, with the help of the entertainment industry, to police content for themselves, a prospect the senator deems unacceptable.

“Overworked and stressed parents cannot be expected to always prevent their kids from viewing inappropriate content across a variety of devices,” Rockefeller said.