Effect of viewing smoking in movies on adolescent smoking initiation: a cohort study.

BACKGROUND Exposure to smoking in movies has been linked with adolescent smoking initiation in cross-sectional studies. We undertook a prospective study to ascertain whether exposure to smoking in movies predicts smoking initiation. METHOD We assessed exposure to smoking shown in movies in 3547 adolescents, aged 10-14 years, who reported in a baseline survey that they had never tried smoking. Exposure to smoking in movies was estimated for individual respondents on the basis of the number of smoking occurrences viewed in unique samples of 50 movies, which were randomly selected from a larger sample pool of popular contemporary movies. We successfully re-contacted 2603 (73%) students 13-26 months later for a follow-up interview to determine whether they had initiated smoking. FINDINGS Overall, 10% (n=259) of students initiated smoking during the follow-up period. In the highest quartile of exposure to movie smoking, 17% (107) of students had initiated smoking, compared with only 3% (22) in the lowest quartile. After controlling for baseline characteristics, adolescents in the highest quartile of exposure to movie smoking were 2.71 (95% CI 1.73-4.25) times more likely to initiate smoking compared with those in the lowest quartile. The effect of exposure to movie smoking was stronger in adolescents with non-smoking parents than in those whose parent smoked. In this cohort, 52.2% (30.0-67.3) of smoking initiation can be attributed to exposure to smoking in movies. INTERPRETATION Our results provide strong evidence that viewing smoking in movies promotes smoking initiation among adolescents.