Teen sleep needs average 9 hours a day, say the experts, but most don't get it. There's a whole cluster of reasons for that, but a growing one is late-night cell phone use. Several studies have looked at this trend -- e.g., the epidemic of teens sleeping with phones under their pillow, which to adults "sounds like torture," CMCH's Michael Rich, M.D. observed wryly -- and found negative consequences. "Hypertexting" teens -- those who text 120 times or more on an average school day -- are especially prone to problems with schoolwork, stress, and depression.
So if you care about your friends, resist the urge. Text before 10 or wait 'til the next day. Your pals will still be there for you, and in much better shape to offer advice and support once they've had some shut-eye.