This is the first study to quantify the risk that tobacco marketing poses to youth, Wellman said in a phone interview.
Other studies have illustrated this risk, but haven't measured just how large it is, he contends.
Wellman and three co-authors performed a meta-analysis, meaning they analyzed 51 studies conducted worldwide since 1981. The studies included 149,949 total participants under age 18.
"The tobacco industry has been arguing for years that their ads are designed to appeal only to those who already use tobacco," Wellman said.
If that were true, children exposed to tobacco marketing would smoke at the same rate as other children.
But this is far from the case, said the behavioral sciences professor, who also teaches at UMass Medical School in Worcester.
"We blew away the tobacco company's argument," he said.
More marketing?
The study also found that the Master Settlement Agreement, a 1998 agreement between the tobacco industry and 46 states, has not reduced the risk of youth-targeted tobacco marketing.
In fact, studies published since 2001 show a higher level of youth susceptibility to tobacco ads.
"You go past a convenience store, and there are cigarette ads plastered up all over the outside, where you can't escape it," Wellman said. "Kids go to convenience stores."
The 1998 agreement banned tobacco advertisements on billboards and buses, and in venues that attract children, Wellman said. But tobacco companies still advertise in magazines like "Cosmopolitan" or "Sports Illustrated," which young people read, he said.
And cigarettes haven't disappeared from films or television either, despite the settlement's stipulation that tobacco companies stop paying Hollywood producers for tobacco placement.
"Movie smoking is currently at a level that hasn't been seen since the '50s and '60s," Wellman said. "It dipped for a long time, but it's gone way up now."
Wellman and his colleagues also found that psychological involvement in tobacco media is even more powerful than other exposure, and makes a child almost three times more likely to smoke.
"If the kid's favorite actor smokes, that's more engaging than someone else smoking in a movie," Wellman said.
An Internet video is also more engaging, because it requires the child to interact with the computer.
Sexually provocative advertisements can be more engaging too, the professor said.
Because it incorporates over 20 years' worth of research, Wellman's study makes a bold statement. It should advise parents to be vigilant about what television and movies their children watch, he said.
The study, titled "The Extent to Which Tobacco Marketing and Tobacco Use in Films Contribute to Children's Use of Tobacco: A Meta-analysis," was published in the December 2006 issue of the Archives of Pediatrics and Adolescent Medicine.
Wellman's co-authors were physician Joseph R. DiFranza, of UMass Medical School, David B. Sugarman, a professor at Rhode Island College, and Jonathan P. Winickoff, a physician at Mass General Hospital and the Harvard Medical School.
The study was funded by a $90,000 grant from the Robert Wood Johnson Foundation's Substance Abuse Policy Research Program