Some 500 Internet message boards are bringing together adolescents who injure themselves -- with cuts, carvings, scratches or burns. It is a world that is invisible to adults but of increasing importance to teenage social lives.

A new Cornell University study finds that the message boards give many isolated teenagers a safe place to share this intimate secret.

But although the majority of the postings are supportive in nature, some reinforce self-injury behaviors and could create a "social contagion" effect, the researchers warned.

"Internet message boards provide a powerful vehicle for bringing self-injurious adolescents together, and to a great extent, they provide a safe forum and a source of valuable support for teens who might otherwise feel marginalized and who may be struggling with shame," said Janis Whitlock, director of the Cornell Research Program on Self-Injurious Behaviors and the first author of the study, which is published in the May 2006 special issue of Development Psychology on use of the Internet by children and adolescents.

In an analysis of more than 3,200 postings on 10 message boards with a focus on self-injury (there were 406 such boards at the time of the study, and now there are more than 500), the Cornell researchers found that the leading type of posting was supportive (28 percent), followed by discussions of triggers and motivations (almost 20 percent) and concealment (9 percent). About 6 percent of postings asked for or shared techniques. Most board postings were from females describing themselves as between 14 and 20 years of age.

Self-injurious behavior is defined as inflicting harm to one's body without the obvious intent of committing suicide and may also include ripping or pulling skin or hair, biting, punching or banging oneself, bruising and breaking bones.

"On the one hand, the boards provide a positive environment, since healthy social and emotional development hinges on teens' ability to establish caring, meaningful relationships, to find acceptance and belonging in social groups and to establish interpersonal intimacy," said Whitlock. "The Internet makes possible what hasn't been possible before -- youths who would never have found each other now are coming together."

"They can easily find each other 24/7, and adults are clueless that this is going on," added Jane Powers, a senior research associate at Cornell and a co-author of the study.

On the other hand, the researchers warn, the message boards -- which are largely unregulated and unmoderated -- may expose vulnerable youths to a subculture that normalizes and encourages self-injury behavior that could be addictive, even lethal. "Easy access to a virtual subculture of like-minded others may reinforce the behavior for a much larger number of youth," said Whitlock.

"A small percentage [of the postings] reinforce negative aspects of the behavior, teaching kids how to do it, how to cut better or deeper, how to get paraphernalia," added John Eckenrode, professor of human development at Cornell and the third co-author of the paper.

The study also reflects the changing nature of adolescent support systems and provides a window into how virtual space has become as important for development as schools and neighborhoods and is even replacing the mall as a primary place for social interaction, said the researchers.

"Our greatest concern is that it could be difficult to leave the behavior if you've finally found a community that you never had before," noted Eckenrode. "Another concern is that this could be a toxic virtual environment that kids are stumbling into, just the way kids stumble into people who are predatory."

Although few studies have examined the prevalence of self-injury, current estimates suggest that from 10 percent to 14 percent of teens have self-injured. However, the Cornell researchers said they will reveal "some startling findings" on the prevalence of self-injury in a major, representative college-age sample in the June issue of Pediatrics.

For more information on self-injury and the Cornell Research Program on Self-Injurious Behaviors, see http://www.crpsib.com.