MONDAY, Jan. 14 (HealthDay News) -- Nearly a third of American teenage girls say that at some point they've met up with people with whom their only prior contact was online, new research reveals.

For more than a year, the study tracked online and offline activity among more than 250 girls aged 14 to 17 years and found that 30 percent followed online acquaintance with in-person contact, raising concerns about high-risk behavior that might ensue when teens make the leap from social networking into real-world encounters with strangers.

Girls with a history of neglect or physical or sexual abuse were particularly prone to presenting themselves online (both in images and verbally) in ways that can be construed as sexually explicit and provocative. Doing so, researchers warned, increases their risk of succumbing to the online advances of strangers whose goal is to prey upon such girls in person.

"Statistics show that in and of itself, the Internet is not as dangerous a place as, for example, walking through a really bad neighborhood," said study lead author Jennie Noll, a professor of pediatrics at the University of Cincinnati and director of research in behavioral medicine and clinical psychology at Cincinnati Children's Hospital Medical Center. "The vast majority of online meetings are benign.

"On the other hand, 90 percent of our adolescents have daily access to the Internet, and there is a risk surrounding offline meetings with strangers, and that risk exists for everyone," Noll added. "So even if just 1 percent of them end up having a dangerous encounter with a stranger offline, it's still a very big problem.

"On top of that, we found that kids who are particularly sexual and provocative online do receive more sexual advances from others online, and are more likely to meet these strangers, who, after sometimes many months of online interaction, they might not even view as a 'stranger' by the time they meet," Noll continued. "So the implications are dangerous."

The study, which was supported by a grant from the U.S. National Institutes of Health, appeared online Jan. 14 and in the February print issue of the journal Pediatrics.

The authors focused on 130 girls who had been identified by their local Child Protective Service agency as having a history of mistreatment, in the form of abuse or neglect, in the year leading up to the study. The research team also evaluated another 121 girls without such a background.

Parents were asked to outline their teen's routine habits, as well as the nature of any at-home Internet monitoring they practiced, while investigators coded the girls' profiles for content.

Teens were asked to report all cases of having met someone in person who they previously had only met online in the 12- to 16-month period following the study's launch.

The chances that a girl would put up a profile containing particularly provocative content increased if she had a history of behavioral issues, mental health issues or abuse or neglect.

Those who posted provocative material were found to be more likely to receive sexual solicitations online, to seek out so-called adult content and to arrange offline meetings with strangers.

Although parental control and filtering software did nothing to decrease the likelihood of such high-risk Internet behavior, direct parental involvement and monitoring of their child's behavior did mitigate against such risks, the study showed.

Noll said concerned parents need to balance the desire to investigate their children's online activities -- and perhaps violate a measure of their privacy -- with the more important goal of wanting to "open up the avenues of communication."

"As parents, you always have the right to observe your kids without their knowing," she said. "But I would be careful about intervening in any way that might cause them to shut down and hide, because the most effective thing to do is to have your kids communicate with you openly -- without shame or accusation -- about what their online lives actually look like."

Dr. Jonathan Pletcher, clinical director of adolescent medicine at the Children's Hospital of Pittsburgh, said "there's no one-size-fits-all parenting for all of this."

"It's really about building a foundation of knowing your kid and knowing their warning signs and building trust and open-minded communication," he said. "[You have to] set up that communication at an early age and establish rules, a framework, for Internet usage, because they are all going to get online.

"At this point, it's a life skill that has become almost essential for teens, so it's going to happen," he added. "What's needed is parental supervision to help them learn how to make these online connections safely."

More information

For more about teen development, visit the U.S. National Institutes of Health.