Some public health myths, no matter how absurd or consistently refuted, just refuse to die a dignified death.

One of the most pervasive is the claim that the more teens see tobacco in movies the more likely they are to pick up smoking. Every time a new study comes out documenting tobacco use on the big screen, a minor panic ensues.

Such a report, released last month, showed the use or implied use of tobacco in top-grossing movies rose 72 percent from 2010 to 2016. In PG-13 movies these "tobacco incidents" rose 43 percent, and there was a 90 percent increase for R-rated movies. (It should be noted the researchers decided to include e-cigarettes in their category of tobacco incidents, despite e-cigarettes containing zero tobacco).

The study garnered extensive media coverage, with almost all outlets taking it as gospel that this was an issue of public concern. Claims there is a wealth of strong evidence suggesting scenes featuring tobacco in movies actually cause teens to smoke went repeated without question.

This narrative has largely been driven by one man: a mechanical engineer turned professor of medicine and fanatical anti-tobacco campaigner named Stanton Glantz. A co-author of the report and founder of Smokefree Movies, Glantz has spent years trying to get Hollywood to slap an R rating on films featuring tobacco.

To justify this intrusion on artistic freedom, Glantz claims tobacco in movies plays a bigger role in teens' decision to smoke than peer or parental influences, accusing the movie industry of being culpable for the deaths of hundreds of thousands of people who have taken up smoking.

This bizarre claim is based on a literature manufactured primarily by Glantz and a handful of other researchers. While there is a substantial body of literature on the subject, the evidence supporting Glantz's position is nonexistent.

The assumption that tobacco in movies causes teen smoking is based on research examining teens who have seen movies with many smoking scenes, compared to those who haven't. This research shows teens who saw more smoking scenes are more likely to try cigarettes than those who hadn't.

The fundamental problem with this research is that it is impossible to establish a causal relationship between seeing tobacco on screen and smoking while controlling for other factors.

We know that teenagers who are more likely to start smoking are also more likely to engage in a host of other risky behaviors such as underage drinking, drug use, and unprotected sex. It is therefore not unreasonable to assume these teens are attracted to certain kinds of movies. These teens may be more likely to pick movies with themes that heavily feature action, crime, alcohol, sex, and drug use.

Almost none of the research supporting this theory even tries to disentangle these factors. In fact, the failure of most research to account for this glaring problem led one of the world's most militant anti-smoking campaigners Simon Chapman, to call this kind of research "epidemiological alchemy."

Writing in PLOS Medicine in 2014, Chapman and his co-author Matthew C. Farrelly highlighted the problems facing Glantz.

"Self-selection is key to understanding what it might be that characterizes the association between young smokers having seen many such movies and their subsequent smoking," write Chapman and Farrelly. "Indeed, it may be more accurate to say that certain movies are more predictive of future smoking behavior than smoking is a causal factor," they added.

When researchers do account for these variables, the strength of Glantz's already weak case rapidly diminishes. A 2011 study which examined 71 top-grossing films over 4-years found "the correlation between exposure to smoking in the movies and other adult content (nudity, violence, profanity) was so high that it was impossible to disentangle their separate influence."

Not only that, but over the same period that Glantz's study says tobacco in movies has been rising, teen smoking has been dropping like a stone, falling to the lowest level on record in 2016. Yet Glantz would still have us believe tobacco movies is the biggest determinant of teens picking up smoking.

Besides the lack of evidence showing a causal link between smoking in movies and smoking initiation, it is bizarre to imagine that slapping an R rating on movies will stop teens from seeing the kinds of movies that feature smoking.

Teens can pretty readily view whatever they want online. It is nigh impossible to prevent teens from watching porn, let alone protecting them from the horrors of seeing a Marlboro Light.

Thankfully, despite the years of garbage research and gullible reporters willing to regurgitate it, the Motion Picture Association of America has consistently refused to give into the bullying from tobacco control loons and told them in no uncertain terms to butt out.

Guy Bentley (@gbentley1) is a contributor to the Washington Examiner's Beltway Confidential blog. He is a consumer freedom research associate at the Reason Foundation and was previously a reporter for the Daily Caller.

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