Scientific studies consistently demonstrate that smoking in the movies stimulates kids to smoke. For example, comparing kids’ attitudes towards smoking before and after watching a movie with smoking moves kids' attitudes in a pro-smoking direction.

Such experiments have been complemented with surveys of large numbers of children asking them whether or not they smoke and what movies they have seen or who their favorite stars are that demonstrate, after accounting for other factors that determine smoking such as whether their parents smoke or how the kids are doing in school, the kids who have seen a lot of smoking in the movies or have favorite stars that smoke are more likely to be smokers. These "cross-sectional studies" are a snapshot. While providing strong evidence, by themselves they are not conclusive. For instance, what if teens who smoke simply prefer to watch movies with smoking in them. To be certain of cause-and-effect, researchers need to follow kids over time.

In 2003, a research group at the Dartmouth Medical School Department of Pediatrics substantially strengthened the case that smoking in the movies causes adolescent smoking. They conducted a "longitudinal study" in which they recruited 2603 adolescents (age 10-14) who had never tried smoking, collected detailed information about attitudes and other factors that predict smoking, then followed the adolescents for 13-26 months later to see who started smoking.

They did not just look at who started smoking. They also took into account other factors that have been linked to adolescent smoking, including:

• grade in school
• gender
• school
• friend smoking
• sibling smoking
• parent smoking
• receptivity to tobacco advertising and promotions
• school performance
• sensation-seeking propensity
• rebelliousness
• self esteem
• parent’s education
• authoritative parenting
• perception of parental disapproval of smoking

The Dartmouth scientists then followed them forward in time for 13-26 months and found that 10% of the kids started to smoke.

After controlling for the effects of all the other factors they considered, kids who saw the most smoking in movies were nearly three times as likely to have started smoking than kids in the lowest exposure group.

As was demonstrated in earlier “snapshot” studies, there is a “dose-response effect:” The more on screen smoking the kids saw, the more likely they were to have started to smoke. The existence of this dose-response relationship not only strengthens the scientific case, but it also means that steps to reduce the “dose,” particularly an “R” rating for smoking in movies, will lead to less teen smoking.

This effect is stronger in kids of nonsmoking parents than parents who smoke. Kids of nonsmoking parents in the most-exposed group are 4.1 times as likely to have started smoking compared to those in the lowest exposure group. This effect is substantially stronger than the increase by “only” 1.6 times among kids of smoking parents.

Smoking in the movies accounted for 52% of the kids who started smoking, a stronger effect than traditional cigarette advertising. (Big Tobacco has understood this fact for decades. Read their secret efforts to get smoking into the movies.)

In 2005, the same team of pediatricians, scientists, and epidemiologists at Darmouth did a followup study using a national sample of 6500 adolescents to make sure that the results from the New England study held up nationally. This large national study showed essentially the same risks for starting smoking in this national sample as was observed in New England.

Applying these results nationwide, means that 390,000 kids start to smoke every year because of the movies, 120,000 of whom will die as a result.

And because half the smoking in movies that kids see is in youth-rated (G/PG/PG-13) movies, smoking in youth-rated films accounts for about 200,000 kids a year starting to smoke, 60,000 of whom will die as a result.

That's why getting smoking out of youth-rated films (by rating movies with smoking "R") would be a real life saver.