CHICAGO (AP) — Add "Facebook depression" to potential harms linked with social media, an influential doctors' group warns, referring to a condition it says may affect troubled teens who obsess over the online site. 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.