"Young adults who are constantly logging onto the world's largest social networking Web site are more likely to display narcissistic tendencies...."
Or, could it be that those with narcissistic tendencies like updating their status constantly?
"...teens with a strong presence on Facebook may exhibit potentially adverse effects such as antisocial behavior, mania and depression. "
Or, er, shy kids find it easier to communication online? Depressed kids don't have the energy to get out of the house?
"For instance, while researchers found that middle, high school and college students who logged onto Facebook at least once during a 15-minute study period were more likely to receive lower grades on exams."
How did this compare with kids back in my day (that is, the day of the walking uphill in the snow to school both ways, when cars were a shiny nickel!) who passed notes during study period? Or, for that matter, kids today who do anything non-study related during study period?