Compared to those who don’t smoke illicit tobacco, kids who do are more likely to try other illegal drugs like cocaine, heroin and amphetamines, according to a recent Canadian study.

The researchers used survey data from one point in time, so they can’t say that smoking illegal cigarettes leads to drug use, only that the two often coincide and that’s enough to warrant stronger tobacco control policies.

“The concern for us is that contraband tobacco may be a gateway to other drugs, but we cannot infer causality,” said coauthor Mesbah F. Sharaf of the economics department at the University of Alberta in Edmonton.

In Canada, unmarked and untaxed contraband cigarettes are either illegally manufactured domestically or illegally imported across the U.S. border, often from Native American reservations, the authors write in The Journal of Primary Prevention.

They cite a national survey from 2007 that found 18 percent of all cigarettes used by teens who smoked daily were contraband.

“Here in Canada the contraband market is really substantial, almost 30 percent of tobacco sales in the whole country,” Sharaf told Reuters Health.

For the new study, he and his coauthors used data from Canada’s 2010-2011 Youth Smoking Survey, a school-based survey of kids in grades six through 12.

It included questions about smoking unbranded or Native American-brand cigarettes over the previous twelve months as well as use of amphetamines, cocaine, heroin, ecstasy and ketamine over the same period.

Focusing on the answers from kids who smoked, the researchers found that 31 percent of them had used contraband cigarettes at least once in the previous year. And contraband cigarette smokers were more likely to report using other drugs than kids who only smoked legal cigarettes.

Twenty percent of contraband cigarette users reported trying heroin, compared to three percent of non-contraband smokers. For hallucinogens, 46 percent of contraband smokers reported trying it, compared to 30 percent of non-contraband smokers.

“The issue of illicit tobacco is a prominent problem worldwide,” said Dr. Russ Callaghan, associate professor in the Northern Medical Program at the University of Northern British Columbia in Prince George, who was not part of the new study.

“In general, the way it is defined is any tobacco product that doesn’t have the full set of taxes or levies applied to the purchase price,” Callaghan told Reuters Health.

Illicit tobacco is less of an issue for kids in the U.S., but it is contributing to a lot of youth smoking in Canada, and the tobacco products they get largely come across the border from upstate New York, he noted.

The new study does show an association between contraband tobacco and illegal drugs, but it cannot say anything about causation, which is important, Callaghan noted.

Sharaf cites a Royal Canadian Mounted Police drug bust in which contraband tobacco was found with other illicit drugs as evidence that kids may be getting their illegal cigarettes and other substances from the same source.

“So it seems that this contraband market is managed by probably organized crimes and criminal gangs that may be using contraband as an avenue to other illicit drugs,” Sharaf said. “Most likely it is the same source.”

But in interviews with teen smokers in Canada, Callaghan has not found that to be the case.

“When I’ve asked young people about whether their sources of illicit cigarettes and illicit drugs are the same, they say no,” he said.

Some corner stores sell the cigarettes, which could be where young people purchase them, he noted.

Although the authors suggest the “gateway hypothesis,” wherein illegal tobacco leads to the use of other illegal drugs, “I don’t think they are really warranted in inferring that at all,” Callaghan said.

“I think what’s probably happening here is you have young people who may be marginalized, have low academic achievement, more deviance, and they engage in both of these activities,” he said.

In the past, some have argued that marijuana is a gateway drug to more dangerous substances, and that has been mostly disproved, Callaghan said.

“It’s not that I don’t think that illicit drugs are a problem, but I’d be wary of that particular line of reasoning,” he said. “There’s a relation, but we need to be careful. I hope it’s not alarmist.”

Linking contraband tobacco to further drug use could bring more attention to the problem, but policymakers may argue to lower taxes on legitimate cigarettes to reduce the contraband market, which would in turn lead to cheaper cigarettes and more smokers, Callaghan said.

Earlier this year, Canadian criminal codes were amended to make trade, promotion or sales of contraband a criminal offense, which is a step in the right direction, Sharaf said.

“This needs to be supplemented with creative government measures,” he said.