The number of smoking scenes in movies rated G, PG and PG-13 increased by more than one-third from 2010 to 2011, according to a new report by the Centers for Disease Control and Prevention. The increase signals a reversal after a five-year decline in such smoking scenes, HealthDay reports.

The report, published in the journal Preventing Chronic Disease, found four of the six major Hollywood films showed more smoking in their youth-rated movies compared with the previous year. The biggest jump in smoking scenes occurred in movies from the three major film studios that have published policies on onscreen smoking: Disney, Warner Brothers and Universal.

Youth-rated movies accounted for 68 percent of all tobacco scenes in 2011, compared with 39 percent in 2010. The study suggested that the movie rating system should be modified to give films with any tobacco use an R rating.

The report was funded by Legacy for Health, a national public health group that seeks to reduce tobacco use in the United States. “These data show us that individual policies that movie studios created in good faith to address this important public health problem do not stand up,” Cheryl Healton, Legacy President and CEO, said in a news release. “The only way to ensure a substantial and permanent reduction in young people’s exposure to onscreen smoking is for the movie industry to adopt a uniform set of policies that apply to all producers and distributors, and provide structural incentives for lasting change.”

A study published this summer suggests that children ages 10 to 14 who view many movies with characters who smoke are more likely to try cigarettes themselves.