Rating movies that depict smoking with an “R” could substantially reduce smoking onset in adolescents, a new study suggests.

Smoking’s connection to cancer, heart attacks and chronic lung disease has been proven, said the study’s lead author, Dr. James Sargent, of the Norris Cotton Cancer Center at Dartmouth Medical School.

“Kids start to smoke before they're old enough to think about the risks; after starting they rapidly become addicted and then regret it. Hollywood plays a role by making smoking look really good,” he said.

"By eliminating smoking in movies marketed to youth, an R rating for smoking would dramatically reduce exposure and lower adolescent smoking by as much as one-fifth."

The study, published in the August issue of the journal Pediatrics, involved 6,522 U.S. adolescents who were interviewed at eight-month intervals.

Researchers measured movie smoking exposure (MSE) from 532 recent hit movies, which were categorized into three of the ratings brackets used by the Motion Picture Association of America (MPAA) to rate films by content: G/PG, PG-13, and R.

MPAA ratings apply in the U.S. only. In Canada, each province has its own film classification system.

Median smoking exposure among teens who viewed PG-13 movies was approximately three times higher than from R-rated films but their relation to smoking was essentially the same.

The researchers concluded that adolescent smoking would be reduced by 18 per cent if smoking in PG-13 movies was largely eliminated, all else being equal.

"The equivalent effect of PG-13-rated and R-rated MSE suggests it is the movie smoking that prompts adolescents to smoke, not other characteristics of R-rated movies or adolescents drawn to them," the study concludes.

"We're just asking the movie industry to take smoking as seriously as they take profanity when applying the R rating," Sargent said. "The benefit to society in terms of reduced health-care costs and higher quality of life is almost incalculable."