The study was conducted by a research branch of the National Institutes of Health and released Tuesday morning.
Bruce Simons-Morton, who led the study, wrote in a report that "peer pressure was positively associated with drinking for girls and not boys."
The data were developed from confidential surveys on drinking and smoking given to 4,200 teens in Maryland's junior high schools.
The notion that girls may be swayed by their friends more easily than boys is supported by many experts who have studied the subject.
"I'm not surprised at all. Girls go through this tremendous emotional and hormonal change as you they go to seventh grade," said Shannon McLinden, an author on the subject and a speaker on teen-age confidence.
"The change comes at a time when being your own person and trying to stand on your own feet is really important."
The new study also showed that for boys and girls, the top indicator of whether youngsters begin drinking or smoking is whether they have friends who do, Simons-Morton said. The conclusion remains true regardless of whether the friends are overtly pressuring the teen-ager, the study reports.
"We found that the single most important factor is the behavior of their five closest friends," said Simons-Morton. "These teens are nine times more likely to smoke than early adolescents who had no friends that smoke or drink."
The finding suggests that traditional images of peer pressure a dare given at a party, or a joke made at the expense of a nondrinker may not always be the prime catalyst for a young person's decision.
Instead, Simons-Morton said, many teens seem to mimic the behavior of friends.
Also impacting the situation: most teens who drink and smoke think their parents don't care.
"Teens who said their parents would be upset if they were caught drinking or smoking were much less likely to drink or smoke, and the opposite is also true," Simons-Morton said.
In step with other recent studies, Simons-Morton also found that parents involved in their children's lives engaging in regular conversations, attending after-school events, listening to their problems were less likely to have children who drank or smoke.
The study also reflected recent research that has many social scientists stumped: White teen-agers drink and smoke at a higher rate than black teen-agers.
"We don't know why this is true, but it fits with other major research," Simons-Morton said. "It is something many people are looking into."