FRIDAY, March 18 (HealthDay News) -- Girls in early adolescence who form friendships with boys are at increased risk for substance abuse problems, according to a new research.

The study included 400 female and male participants, ages 12 to 18, in Canada who were interviewed annually over seven years about their friendship network and use of alcohol and drugs.

In childhood, boys and girls tend to limit their friendships to same-sex peers. But this begins to change around early adolescence. This study found that girls tend to make the change to mixed-gender friendships earlier than boys, and continue this transition at a more rapid pace through adolescence.

The researchers also found that girls who did move to mixed-gender friendships early and quickly are more likely to develop substance abuse problems during late adolescence.

Antisocial behavior and early physical maturity accelerated the increase in girls' numbers of male friends, who tended to be older and who didn't go to the same school. This may be because older boys provide younger girls with a way of obtaining alcohol, said the researchers.

They said their findings suggest that parents may want to more closely monitor their daughters' friendships, especially with older boys.

The study appears in the Journal of Research on Adolescence.

"Peer relationships are considered to be one of the main risk factors for substance use. However, for boys, the formation of other-sex friendships is not associated with later substance use problems," lead author Francois Poulin, a professor of psychology at the University of Quebec at Montreal, said in a journal news release.

"Boys reported receiving higher levels of emotional support from their other-sex friends, whereas girls receive more support from their same-sex friends," Poulin explained. "It is possible that having other-sex friends is protective for boys because they gain emotional support and are therefore less likely to engage in problem behavior."

More information

The U.S. National Institute on Alcohol Abuse and Alcoholism has more about underage drinking.