Kenny told us they wake up several times during the night to text. Kenny even sleeps with his phone beneath his pillow. Dr. Dowdell says that its common for teens' sleep to be interrupted by texts. Sometimes teens even send texts filled with nonsense words when they don't wake up all the way. She has been studying this trend, which she calls "sleep texting." Why is sleep texting a problem? "Adolescents need a solid 8, 10, even 11 hours of sleep to really function and to think clearly," reports Dr. Dowdell if they regularly lose sleep, she adds, teens may start having trouble in school. They may become grumpy, angry, or depressed. A lack of sieep can lead to weight gain and even obesity. That's because many people turn to junk food for quick chergy when they are tired. FACT: 4​