TORONTO - High-school students who take part-time jobs for pocket money may be more likely to start smoking than teens who don't join the after-school and weekend workforce, a study suggests.

The study of Grade 10 and 11 students in Baltimore shows that those who took jobs, often in retail outlets and fast-food or other restaurants, had a greater propensity to begin lighting up - and that trend was strongest among teens who worked the most hours per week.

"Of those who didn't smoke at Grade 10, kids who (began working) were at least three times more likely to start smoking than kids who didn't start working," lead author Rajeev Ramchand, a psychiatric epidemiologist, said Thursday from Arlington, Va.

"What we found was the kids who worked more than 10 hours a week on average had an earlier age of initiation. So they started to smoke ahead of their peers," said Ramchand, who conducted the study with colleagues while a graduate student at the Johns Hopkins School of Medicine in Baltimore, Md. He now works for the Rand Corp.

"That says that maybe there's something going on that says kids start smoking when ... they go to work or work a lot."

The researchers posit a number of reasons for the change in smoking status: For one, teens may be exposed on the job to older youth or to adults who are more likely to smoke and where smoking is more common and acceptable, said Ramchand, who originally hails from Niagara Falls, Ont.

"Second is that they can now buy cigarettes, as before they may have not had the means, the money, to buy cigarettes," he said.

Taking a part-time job also changes a teen's relationship with family members, said Ramchand, and that can strongly affect behaviour.

"When kids start working, we know from previous research, their bonds with their parents tend to weaken. So whereas in the past some have proposed that your bonds to your parents actually prevent you from drug-using behaviours like tobacco smoking, when you work, a parent kind of releases those bonds and ... that freedom may increase the likelihood to smoke."

The work itself may also contribute to the decision to pick up the habit, he said. Often repetitive and monotonous, part-time jobs may make taking a smoke break a means of escaping boredom.

Stress may also be another factor, Ramchand offered.

"Kids don't report that their jobs themselves are very stressful, but what they will report is that managing their time and their responsibilities - getting all their homework done, sports if that's part of their lives, as well as their work responsibilities - the combination of those things creates stress.

"And they may turn to cigarettes as a kind of self-medication to relieve that stress."

The research, published Friday in the American Journal of Public Health, is part of a larger ongoing study of almost 800 Baltimore children, who were enrolled in Grade 1.

Dr. Roberta Ferrence, executive director of the Ontario Tobacco Research Unit, said she is not surprised at the findings.

Besides providing income to pay for smokes, having a job also offers an opportunity to indulge the habit.

"If you're in a workplace, you're away from your parents, you're away from the social controls you might have if you were at school or at home," said Ferrence, who's also a senior scientist at the Centre for Addiction and Mental Health in Toronto.

"So you may be more likely to have the freedom to smoke and nobody's going to see you who might tell you not to."

The study authors say too little focus has been given to the workplace as an environment that may promote teen smoking behaviour - or as a potential means for keeping kids smoke-free.

Ramchand said workplaces could be ideal sites for smoking-prevention programs aimed at teens, although it's difficult to predict whether employers would buy into the concept.

"I think what makes more sense," said Ferrence, "is to make sure if they're working that they're working in smoke-free workplaces, because we do know that bans in homes, in workplaces, wherever, they do reduce smoking initiation, increase cessation and reduce relapse."

"Let's make sure there is no smoking in any hospitality-sector or other workplaces, and that should reduce the risk."