Amy Bleakley is a research scientist at the University of Pennsylvania who was a co-author of the study appearing in the latest edition of the journal Pediatrics. She said the PG-13 rating, determined by the Motion Picture Association of America, doesn't always stop the kind of material parents may think it does.
"We found that there is really no difference between PG-13 and R-rated movies with regards to the extent to which the extent of this content is featured, except with tobacco and explicit sex, which is more common in R-rated movies," Bleakley said.
The study looked at 400 of the top-grossing movies released from 1985 to 2010. In nine out of 10, on average, the movies showed a main character involved in violence, and in just under eight of 10 movies, the main character was in scenes showing other risky behavior, such as drinking or sexual activity.
According to Bleakley, the big question, even after the release of this study, revolves around how children process what they see at the movies and whether they are more likely to act out on a broad range of risky behaviors.
"We know that when kids see just tobacco on screen, they're more likely to initiate smoking, and when they see alcohol on screen, they're more likely to drink, and so on. But we don't know the effect of these clustered behaviors. So that's our next step. We want to try and find that out, she said.
Parents can review the Motion Picture Association of America's definitions of what it intends each rating category to mean on the MPAA website.
The full study is available at bit.ly/1e1yDzv.