Understanding the Zombie Teen's Body Clock

Many parents know the scene: The groggy, sleep-deprived teenager stumbles through breakfast and falls asleep over afternoon homework, only to spring to life, wide-eyed and alert, at 10 p.m.—just as Mom and Dad are nodding off.

Fortunately for parents, science has gotten more sophisticated at explaining why, starting at puberty, a teen's internal sleep-wake clock seems to go off the rails. Researchers are also connecting the dots between the resulting sleep loss and behavior long chalked up to just "being a teenager."...