The research was conducted by a team from the University of California, San Francisco. Previous studies from around the world found that viewing on-screen smoking was linked to recruitment of adolescent smokers, but this is the first time that smoking among young adults has been associated with their exposure to smoking scenes on screen, said senior author Stanton Glantz, PhD, professor of medicine and director of the UCSF Center for Tobacco Control Research and Education.

"Ages 18 to 25 are critical years, when one-third of smokers start and others who began smoking as adolescents either stop smoking or become regular smokers," he said.

The research team found a "dose-response relationship" between exposure to smoking on screen and the likelihood of having smoked in the past 30 days in a sample of 1,528 young adults. The study findings are published in the November issue of the "American Journal of Preventive Medicine."

Young adults who saw the most smoking on screen have a 77 percent greater chance of having smoked at least once in the last 30 days (a measure of smoking initiation) and an 86 percent increased chance of being regular established smokers compared to young adults who saw little smoking in movies, the study showed. "Established smokers" are defined as those who have smoked 100 cigarettes or more and currently smoke.

Participants in the study reflected a cross-section of the U.S. population for the age group, and they took part through a web-based survey. Of the study group, 24.7 were smokers, comparable to estimates of the Centers for Disease Control and Prevention of 25.3 percent for this population. The survey format was similar to the studies of adolescents, with participants receiving a list of 60 motion pictures, selected at random from the top grossing 500 movies released during 2000-2004, and asked to identify the movies they had seen. Each participant was then placed in a quartile of exposure based on the sum of tobacco occurrences that had been viewed.

The results showed a direct effect between exposure and current smoking. The researchers found that two factors mediated the association between exposure to film smoking and established smoking: positive expectations about smoking and exposure to friends and relatives who smoke.

"The main effect is to recruit new smokers from among young adults," Glantz noted. "Movies encourage them to experiment, and once they start experimenting with cigarettes other factors take hold. Movies create the expectation that smoking will turn out okay."

The effect demonstrated in young adults is smaller than effects shown in adolescents, but comparable to other environmental risk factors for smoking initiation in young adults, he emphasized.

For example, in the 18-25 age group, researchers estimate that exposure to tobacco promotions in clubs and bars and at campus social events boosts the odds of 30-day smoking by a factor of 1.75, close to the risk of 1.77 posed by exposure to smoking on screen.

It has been estimated that awarding R-ratings on future tobacco imagery to eliminate smoking from youth-rated films would reduce teen exposure to the imagery by half and prevent about 200,000 youth a year from starting to smoke, Glantz said. The results of the new study indicate that young adults are also being recruited to smoke through their exposure to movie smoking, and a substantial reduction in smoking content has the potential to avert even more tobacco deaths, he added.

The research was funded by the National Cancer Institute.

UCSF study co-authors are Anna Song, PhD, a postdoctoral fellow in the Center for Tobacco Control Research and Education; Pamela Ling, MD, assistant professor of medicine, and Torsten B. Neilands, PhD, of the Center for AIDS Research.

Note: If no author is given, the source is cited instead.

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