BOSTON – A Massachusetts study suggests that restaurant smoking bans may play a big role in persuading teens not to become smokers.

Youths who lived in towns with strict bans were 40 percent less likely to become regular smokers than those in communities with no bans or weak ones, the researchers reported in the Archives of Pediatrics & Adolescent Medicine.

"When kids grow up in an environment where they don't see smoking, they are going to think it's not socially acceptable," said lead author Michael Siegel, of Boston University School of Public Health. "If they perceive a lot of other people are smoking, they think it's the norm."

Dr. Siegel and his colleagues tracked 2,791 children between ages 12 and 17. Massachusetts had no statewide ban when the study began in 2001, but about 100 cities and towns had enacted a hodgepodge of laws.

The teens were followed for four years to see how many tried smoking and how many eventually became smokers. About 9 percent became smokers – defined as smoking more than 100 cigarettes.

The study found that having a smoker as a parent or a close friend was a factor in predicting whether children experiment with cigarettes. But strong bans had a bigger influence on whether smoking grew into a habit, reducing their chances of becoming smokers by 40 percent.

"There is really no other smoking intervention program that could cut almost in half the rate of smoking," Dr. Siegel said.

The researchers said it's not clear whether strong bans would have the same effect in other states, since local restrictions were adopted as part of an aggressive anti-smoking campaign throughout Massachusetts.