Researchers disagree on whether it's simply an extension of depression some kids feel in other circumstances, or a distinct condition linked with using the online site.

But there are unique aspects of Facebook that can make it a particularly tough social landscape to navigate for kids already dealing with poor self-esteem, said Dr. Gwenn O'Keeffe, a Boston-area pediatrician and lead author of new American Academy of Pediatrics social media guidelines.

With in-your-face friends' tallies, status updates and photos of happy-looking people having great times, Facebook pages can make some kids feel even worse if they think they don't measure up.

It can be more painful than sitting alone in a crowded school cafeteria or other real-life encounters that can make kids feel down, O'Keeffe said, because Facebook provides a skewed view of what's really going on. Online, there's no way to see facial expressions or read body language that provide context.

The guidelines urge pediatricians to encourage parents to talk with their kids about online use and to be aware of Facebook depression, cyberbullying, sexting and other online risks. They were published online Monday in Pediatrics.

The academy guidelines note that online harassment "can cause profound psychosocial outcomes," including suicide. The widely publicized suicide of a 15-year-old Massachusetts girl last year occurred after she'd been bullied and harassed, in person and on Facebook.

Facebook is where all the teens are hanging out now. It's their corner store, the benefits of kids using social media sites like Facebook shouldn't be overlooked, however, such as connecting with friends and family, sharing pictures and exchanging ideas.