Christopher Millett of London's Imperial College thinks Casablanca needs an X rating

Movies with smoking scenes should be slapped with adult content ratings, some researchers say.

While Canada and the U.K. have ratified the World Health Organization's Framework Convention on Tobacco Control, they are not yet enforcing it, according to Christopher Millett of London's Imperial College.

He makes the point, along with his co-authors, in this week's issue of Public Library of Science's journal's PloS Medicine.

The convention says all future movies with scenes of smoking should be given an adult content rating, with the possible exception of movies that depict the dangers of tobacco use or smoking by an actual historical figure who smoked.

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