Middle-school students who were exposed to the greatest number of antismoking ads were also the most likely to smoke, according to researchers who concluded that such ads can backfire unless constructed carefully.

The Atlanta Journal-Constitution reported July 19 that researchers at the University of Georgia and the University of Wisconsin at Madison said that the survey of 1,700 middle-school students found that ads that warn about the dangers of smoking may unintentionally encourage the rebelliousness of youth.

"They don't want to hear what they should do or not do," said study co-author Hye-Jin Paek. Instead, ads should try to convince young teens that their peers are rejecting smoking so they should, too.

"Rather than saying, 'don't smoke,' it is better to say, 'your friends are listening to this message and not smoking,'" she said. "It doesn't really matter what their peers are actually doing."

The study is published in the August 2007 issue of the journal Communication Research.