Violence and risky behavior are permeating Hollywood’s most successful movies and bringing a message to young people that violence is acceptable, this according to a new study by the Annenberg Public Policy Center at the University of Pennsylvania.

The study, released Monday by the journal Pediatrics, found that nearly 90% of top-grossing movies over a 25-year period show main characters acting violently, and in 77% of the movies those characters also engage in sex-, alcohol- or tobacco-related behavior.

The study also found that more than half of the biggest PG-13 movies featured a main character acting violently and involved in either drinking, sexual behavior or smoking within a five-minute segment — leading researchers to conclude that movies are “potentially teaching youth that violence is as acceptable as these other behaviors.”

“We know that some teenagers imitate what they see on-screen,” said Amy Bleakley, lead author of the study. “What concerns us is that movies aimed at younger viewers are making a connection between violence and a variety of risky behaviors – sex, drinking and smoking.”

The study, entitled “Violent Film Characters’ Portrayal of Alcohol, Sex, and Tobacco-Related Behaviors,” analyzed characters’ actions in five-minute segments in 390 of the biggest box office movies from 1985 to 2010.

“There’s kind of a James Bond effect, in which violence is glamorized in combination with other behaviors we otherwise try to discourage in youth,” said Dan Romer, a co-author of the study.

Researchers cited James Bond thrillers “Quantum of Solace” (2008) and “Casino Royale” (2006), as well “Mission: Impossible II” (2000). Those films were all rated PG-13 by the Motion Picture Association of America.

The study also found that violent characters appearing in R-rated movies were twice as likely as those in PG-13 movies to engage in “explicit sex” — with researchers finding that occurred in 16.6% of R-rated movies and 7.8% of PG-13 films.