Youngsters who watch movies in which actors smoke a lot are three times more likely to take up the habit than those exposed to less smoking on-screen, a new study of American adolescents suggests.
The study, published Tuesday on the Web site of The Lancet medical journal, provides the strongest evidence to date that smoking depicted in movies encourages adolescents to start smoking, according to some experts. Others said they remain unconvinced.
Many studies have linked smoking in films with increased adolescent smoking, but this is the first to assess children before they start smoking and track them over time.
The investigators concluded that 52 percent of the youngsters in the study who smoked started entirely because of seeing movie stars smoke on screen.
"This effect is stronger than the effect of traditional cigarette advertising and promotion, which accounts for only 34 percent of new experimentation," said Stanton Glantz, a professor of medicine at the Institute for Health Policy Studies at the University of California, San Francisco, who was not connected with the research.
However, Paul Levinson, a media theorist at Fordham University in New York noted there are many reasons people start smoking and the study could not accurately determine how important each factor is.
"It's the kind of thing we should be looking at but ... the fact that two things seem to be intertwined doesn't mean that the first causes the second," said Levinson, who was not involved in the study. "What we really need is some kind of experimental study where there's a controlled group."
The Motion Picture Association of America, which rates movies and represents the movie industry, had no immediate comment.
The research, conducted by scientists at Dartmouth Medical School, involved 2,603 children from Vermont and New Hampshire schools who were aged between 10 and 14 at the start of the study in 1999 and had never smoked a cigarette at the time they were recruited.
The adolescents were asked at the beginning of the study which movies they had seen from a list of 50 movies released between 1988 and 1999.
Investigators counted the number of times smoking was depicted in each movie and determined how many smoking incidents each of the adolescents had seen. Exposure was categorized into four groups, with the lowest level involving between zero and 531 occurrences of smoking and the highest involving between 1,665 and 5,308 incidents of smoking. There were about 650 adolescents in each exposure group.
Within two years, 259, or 10 percent, of the youths reported they had started to smoke or had at least taken a few puffs.
Twenty-two of those exposed to the least on-screen smoking took up the habit, compared with 107 in the highest exposure group - a fivefold difference.
However, after taking into account factors known to be linked with starting smoking, such as sensation-seeking, rebelliousness or having a friend or relative who smokes, the real effect was reduced to a threefold difference.
The researchers also concluded 52 percent of the startup in smoking could be attributed to the movies.
Children of nonsmokers were particularly influenced by smoking in films. Those in the highest movie exposure category were four times more likely to start than adolescents in the lowest group.
In a separate critique of the study, also published by the Lancet, Glantz, who is also a prominent anti-smoking advocate and founder of the U.S.-based Smoke Free Movies campaign, called for an adult, or "R," rating for movies depicting smoking, noting that
60 percent of the total exposure to smoking in movies in the study were in youth-rated films.
Brendan McCormick, spokesman for tobacco manufacturer Philip Morris USA, said depictions of smoking in movies is driven by directors and producers. Tobacco companies do not provide products to moviemakers or pay for product placements, he said.
"We think that producers of films should think very carefully about including depictions of smoking, especially in movies that are likely to be seen by kids," McCormick said.
The study was funded by the U.S. National Cancer Institute.
By Emma Ross