Researchers found that 54 percent of adolescents frequently discuss sexual behavior, substance abuse or violence using MySpace, a popular social networking Web site.

The finding was reported in pair of related studies released by Seattle's Children Research Institute and published in the January 2009 issue of Archives of Pediatric & Adolescent Medicine.

As social networking sites like MySpace.com and Facebook.com become increasingly popular, parents and those who work with teens are concerned the sites might expose teens to ill-intentioned online predators, cyberbullies and increased peer pressure.

There were also fears that what young people post online in personal profiles may affect future university enrollment or job prospects.

MySpace, the most commonly used social networking site, has more than 200 million profiles, with 25 percent belonging to youth under 18, according to several studies.

In one study, researchers collected information from 500 random public MySpace profiles of self-reported 18-year-old males and females from the U.S. and examined to what extent they reported to engage in high-risk behaviors in their profiles.

Researchers found that 54 percent of the MySpace profiles contained high-risk behavior information: 41 percent referenced substance abuse, 24 percent sexual behavior and 14 percent violence.

Females were less likely to have violent information on their profiles than males, and teens who reported a sexual orientation other than "straight" showed increased references to sexual behaviors.

'Dr. Meg' prompted teens to clean up MySpace Act

In another study, many teenagers cleaned up their MySpace profiles, deleting mentions of sex and booze and boosting privacy settings, if they got a single cautionary e-mail from a busybody named "Dr. Meg."

The e-mail was sent by Dr. Megan Moreno, lead researcher of a study of lower-income kids that she says shows how parents and other adults can encourage safer Internet use.

Her message read in part: "You seemed to be quite open about sexual issues or other behaviors such as drinking or smoking. Are you sure that's a good idea?... You might consider revising your page to better protect your privacy."

Parents, and even doctors, who care for adolescents "should feel very comfortable looking up" their children's or patients' profiles on social networking sites like MySpace and Facebook, said Moreno, a pediatrician and adolescent medicine specialist at the University of Wisconsin-Madison. It's not creepy or an invasion of privacy, she said, but more like reading posters on their walls or slogans on their T-shirts.

Young people don't consider the consequences of posting their drinking habits and sexual behavior, Moreno said. Several wrote back to "Dr. Meg" saying they had no idea their pages could be viewed by anyone. Such social networking sites have privacy settings, but they're not always used.

The sites can be a window into a teenager's world.

"People who work with teens often have this idea that teens are hard to reach," she said. But many young people publicly post their hobbies and interests on MySpace or Facebook and expect people to look. "It can be a great icebreaker," she said.

The study, published in the January issue of Archives of Pediatrics & Adolescent Medicine, shows adult supervision of MySpace can raise adolescents' awareness of how accessible their pages are, she said.

The researchers first located 190 MySpace public profiles in a single urban ZIP code, randomly selected from the 10 U.S. Census areas with the lowest average income because researchers wanted to target adolescents who might have less access to doctors. Moreno said she could not reveal the city because of privacy restrictions set by a study review board.

All the users said on their profiles they were 18 to 20 years old and their pages included three or more references to sex, drinking, drug use or smoking.

Half were sent the "Dr. Meg" e-mail; the other half weren't contacted.

After three months, 42 percent of those getting a "Dr. Meg" e-mail had either set their profiles to "private," meaning only people they'd chosen as MySpace "friends" could view it, or they removed references to sex or substance use. Only 29 percent of those in the group who had not been contacted by Dr. Meg made such changes over the three-month period.

Moreno said the results suggest the e-mail intervention had a positive impact on "the hardest-to-reach teens, which gives us great hope that a similar intervention could be used to reach teens as a whole."