Gun violence in PG-13 movies has substantially increased in the past 30 years. The rise in gun use in movies is especially strong since 2000, and this parallels a rise in gun injuries seen in emergency departments in the United States. There has also been a rise in mass shootings over the past 10 years.

Based on these data, some scholars believe that violence in popular media could be a contributor to an uptick in gun injuries among youth. The Annenberg Public Policy Center’s Dan Romer, Patrick E. Jamieson, and Ilana Weitz, along with Brad Bushman, from Ohio State University, outlined this hypothesis in a 2013 study.

“When we see all this gun violence in movies, it makes us stop and think,” says Romer, director of the Adolescent Communication Institute of the Annenberg Public Policy Center. “Movies have been shown to influence adolescents in terms of smoking and drinking, and they probably influence other things that haven’t been studied as much.”

In an article published last year in Human Communication Research, critics challenged the Penn and Ohio State researchers’ theory. They said there is no evidence that trends in gun violence in movies are related to actual homicide rates, referring to statistics that show a decline in violent deaths among youth since the mid-1990s.

But Romer and his colleagues say the mid-’90s was a time when all forms of youth and adult violence began to decline in the United States—it followed a period of rapid increase in the late 1980s that was associated with urban drug use and conflicts, particularly in black and Hispanic neighborhoods.

It’s “just not appropriate” to compare today’s homicide rates with those in the ’90s, Romer says. Besides, he notes, gun injury rates are a more sensitive indicator of the increasing trend in gun violence.

When examining homicides, a better comparison would be to the 1960s, Romer says, adding that violent deaths are still higher today, even with better trauma care.

“Nowadays, if you get shot in North Philadelphia, you’ll end up at Temple Hospital or at the Hospital of the University of Pennsylvania pretty quickly and your life will be saved,” Romer says. “Whereas, in the mid-’60s, you’d be dead. So the fact that the [homicide rates] are just about at the same level as they were in the ’60s is kind of depressing.”

The initial study, published in Pediatrics in 2013, had trained coders look at gun violence trends in movies. Results showed that violence in the most popular films has more than doubled since 1950, and gun violence in PG-13-rated films has more than tripled since 1985, when the rating was established. Since 2009, the study says, PG-13-rated films have contained as much or more violence as R-rated films.

“Slowly the industry started to realize that they could change the movie a little bit, make it more science fiction-y, like with comic book characters, and the ratings board would not regard it as real violence,” Romer says. “PG-13 means [basically] anybody walks in. The R rating at least puts a little bit of a restriction, warning. Rating something PG-13 sends a message to the public and to parents that says, ‘Hey, we think this is OK.’”

The researchers concluded that youth are exposed to increasing gun violence in top-selling films.

The belief that this exposure increases actual violence in youth has not been proven, but Romer says it can be done, just as similar studies measured the effect of tobacco and alcohol in movies on young people’s views.

“Why aren’t we looking at one of the major sources of injury, to see what the impact is?” he asks.

Romer says he and a group of researchers have already submitted a grant proposal to the National Institutes of Health to do a study in Philadelphia and Columbus, Ohio.

“Those are two cities that are quite different,” Romer says. “We want to compare the two cities and we want to watch a cohort of adolescents over time to see what they are watching, what other influences are there in their communities that might affect their willingness to use guns.”

Since the 2013 study, Romer and his colleagues found, in additional research, that the more parents are exposed to violent films, the more comfortable they become with them.

“The data was very clear. Parents who watched a lot of violent movies were much less disturbed by them,” Romer says. “That’s almost scarier in a way, because it’s sort of saying we’re all becoming so used to seeing this kind of content that we don’t even think it’s a problem anymore.”

If guns are being shown in a glamorous way in the movies, Romer says, there’s a chance it is having an impact on young people and potentially even adults.

“We don’t know this,” Romer says, “but we want to find out.”