MONDAY, Jan. 5 (HealthDay News) -- More than half of teens who use the social networking site MySpace have posted information about sexual behavior, substance abuse or violence, new research shows.

The good news, according to a second study from the same research group, is that a simple intervention -- in this case, an-e-mail from a physician -- made some of the teens change their risky behaviors.

"I was surprised, at least to some extent, at how clea...