Washington, Sept. 4 : Teenagers' likelihood of becoming established smokers, a category of smokers who smoke at least 100 cigarettes in their lifetimes, increases with the amount of smoking they see in movies, says a report.

Several previous studies have already shown that more exposure to movie smoking increases teens' risk of starting to smoke, according to background information in an article published in the Archives of Pediatrics & Adolescent Medicine, one of the JAMA/Archives journals.

"However, not all adolescents who try smoking go on to become dependent smokers; half of high school seniors have tried smoking at some time, but only 7 percent are current daily smokers of half a pack or more. Little is known about the factors that discriminate adolescents who progress to dependent smoking from those who do not," the authors write.

Led by Dr. James D. Sargent of Lebanon-based Dartmouth Medical School, a team of researchers surveyed 6,522 US adolescents, aged 10 to 14, about their smoking and movie-watching habits in 2003.

The researchers had already coded displays of smoking in 532 hit movies in the five years prior to the survey. They asked the subjects whether they had seen a random selection of 50 of those films.

Thereafter, a measure of smoking exposure was created by adding the number of smoking occurrences in the portion of those 50 movies that the participant had seen, dividing it by the number of occurrences in the films, and then multiplying it by the number of smoking episodes in all 532 movies.

In order to reassess smoking status, follow-up interviews were conducted after eight months, 16 months and two years.

According to the researchers, 5,637 of the teens had never smoked, while 33 had smoked more than 100 cigarettes at the beginning of the study. By the two-year follow-up survey, 125 of the participants had become established smokers, they said.

The researchers observed that teenagers who were below the midpoint of movie smoking exposure were less likely than those who were above the midpoint to have smoked more than 100 cigarettes.

They got similar results when other factors related to teen smoking-such as age, smoking by a parent or friend and sensation-seeking qualities-were considered.

However, the authors of the study have conceded that the exact mechanism for this association is still unclear.

"The context of current theory and research suggests the most plausible explanation is that frequent exposure to smoking cues in movies leads to more positive expectancies about effects of smoking, more favourable perceptions of smokers and a greater tendency to affiliate with teens who smoke, all factors that increase risk for smoking," they write.

"Combined with previous findings showing that young persons who view more smoking in movies are at increased risk for initiating cigarette smoking, the present findings heighten concern about the public health implications of movie-smoking exposure by linking it with an outcome that predicts smoking-related morbidity and mortality in the future," they conclude. (With Inputs from ANI)