VANCOUVER - Teenagers are trading sex for drugs and alcohol at a low but steady rate, yet the vast majority of them attend school and live at home with their parents, a new University of British Columbia study suggests.

Its lead author says research indicates the problem has been occurring "in the shadows," but that a positive message has also emerged from the findings.

"Family makes a big difference," said co-author and UBC Prof. Elizabeth Saewyc. "When parents talk with kids about their values and goals and when they model healthy romantic relationships, this does influence their own kids' sexual decision-making."

The study involved 2,360 students in Grades 7 to 12 from 28 schools in southeastern B.C. using survey data from a biennial questionnaire conducted by the East Kootenay Addiction Services Society.

Authors of the study, which was published Wednesday in the Canadian Journal of Human Sexuality, say the findings are similar to studies conducted in Quebec, the U.S. and Oslo, Norway.

"Given that it has been documented in other industrialized nations, one would expect this is happening in other parts of Canada and other parts of B.C.," Saewyc said.

She said further studies are needed to learn how pervasive such exchanges are and to help track whether sex-education programs and other prevention strategies are effective.

The study found that just over two per cent of teens who have ever tried alcohol, marijuana or other drugs have also exchanged sex for those substances.

Boys and girls were almost equally likely to make the trade, while 83 per cent of boys and 98 per cent of girls who did so lived at home with family.

"We do know that the kids who felt like they weren't supported or cared about by their families were much more likely to be trading sex for alcohol or drugs," Saewyc said.

Young girls swapping sexual favours with older guys who have cars and money is nothing new, said Diane Sowden, executive director of the Coquitlam, B.C.-based Children of the Street Society.

She said the acts often occur at parties and for something as little as a car ride.

Her organization runs about 500 workshops on sexual exploitation each year, reaching around 30,000 youth around the province.

Sowden has watched teenagers' attitudes shift with education.

"So it's not the norm, and everybody does it and it's just acceptable," she said. "Now you have a youth voice talking on the other side that maybe this isn't the greatest idea, maybe there are risks to this, what other activities can I get involved into get friends without having to exploit myself?"

Repercussions of the behaviour include the risks associated with having a high number of sexual partners and include contracting sexually transmitted infections such as HIV and Hepatitis C.

It's also associated with emotional distress such as suicidal thoughts or self-harm such cutting of the skin.

People who barter for sex with youth in exchange for substances are engaging in child exploitation, Saewyc said.

The study also suggests that teens who are highly impulsive were more likely to engage in trading sex for substances.

Further, it found illicit substances beyond booze and marijuana were more likely to be involved and teens who traded sex also had higher rates of weekly binge drinking compared to other students.

Saewyc said substance-abuse issues were likely associated with the findings, but that social conditioning might be playing a role, too.

"You've got to wonder about the number of songs and media that encourage young people to consider being a hustler, being a ho," Saewyc said.

"That kind of commodification of the sexual relationship ... may lead them to think this is OK."

Saewyc said she hopes the results prompt further discussion both within families and the broader community.

"Contrary to popular opinion, teenagers do listen to their parents," she said. "When there's a strong, caring relationship they really do want to know what their parents think and they want that advice."

The study was funded by the Canadian Institutes of Health Research, a federal government agency.