Smoky Screens

A full-page ad in Friday's New York Times claims a "NATIONWIDE STUDY confirms that exposure to tobacco on screen is a major recruiter of new young smokers." Sponsored by various anti-smoking groups, the ad says that if Hollywood doesn't start giving an R rating to all movies that include smoking, it will be guilty of "knowing recruitment of multitudes of new young smokers by this powerful promotional channel."

The study to which the ad refers, reported in the November issue of Pediatrics, was a national survey of about 6,500 10-to-14-year-olds that found those who saw movies with the most smoking scenes were more likely to have tried cigarettes than those who saw movies with fewer smoking scenes. The survey shares a crucial defect with an earlier study (co-authored by many of the same researchers) that came to similar conclusions: Although the researchers tried to account for a variety of confounding variables, including parental smoking and measures of "rebelliousness" and "sensation seeking," it is not feasible to measure and control for all the personal and environmental factors that make some kids more likely to see smoking-heavy movies, which already tend to be R-rated. It is plausible that adolescents who are both attracted to and able to see more adult-oriented movies are also more inclined and able to experiment with adult habits, regardless of whether seeing smoking in movies makes cigarettes more appealing to them.

The survey has another important weakness: It did not consider which came first, the movie viewing or the smoking, which you'd think would be a minimum requirement for drawing a causal inference. The researchers nevertheless do not hesitate to conclude that "exposure to movie smoking is a primary independent risk factor, accounting for smoking initiation in more than one third of US adolescents 10 to 14 years of age." By contrast, their earlier study, published in The Lancet two years ago, claimed movies were responsible for more than half of smoking initiation. It's true that the new figure (38 percent) falls within the margin of error for the earlier figure (52 percent). But Stanton Glantz's Smoke Free Movies campaign, which was responsible for Friday's ad, seized on the earlier figure and used it to calculate seemingly authoritative numbers of teenagers who never would have smoked were it not for the movies they saw and who would not have died prematurely as a result.

On his tobacco policy blog, Michael Siegel, who thinks smoking in movies probably does contribute to smoking in real life, nevertheless faults his fellow activists for such false precision. In addition to noting the methodological issues I've mentioned, he suggests that "exposure to smoking in movies is likely to represent a proxy measure for a wider constellation of media-related exposures to smoking that likely all contribute to the smoking initiation process." It is both dishonest and tactically unwise, Siegel says, to pretend that research of this sort can untangle and precisely quantify each of these influences. He worries about "the credibility of tobacco control research findings among the public if they are continually exposed to these types of quantitative claims being made from research designs that are simply not 'designed' to produce such claims."