ANNOUNCER: Sleep evolves as we grow. Anyone with a teen can tell you, they seem to sleep away half the morning even though they've got busy lives, trying to pack school, activities and friends into too few hours. Do they really need to log more time in bed than the rest of us?
WOMAN: I think teenagers need more sleep, because their bodies are going through changes so they need that time to energize, for their bodies to grow.
PATRICIA MURPHY, PhD: When children go through puberty, it appears that there's some biological underpinnings that make them need to sleep more.
ANNOUNCER: In fact, teens may even require an entirely different sleep schedule than anyone else.
SONIA ANCOLI-ISRAEL, PhD: You may remember being a teenager and wanting to stay up very late at night and wanting to sleep late in the morning. Most parents think, "Ah, my child is being lazy." But in fact, it's a very normal pattern for adolescents to experience. We call this a delayed sleep phase because their whole pattern is delayed when compared to our environmental clock, to the clock we live by. The biological clock is shifted.
ANNOUNCER: Once the upheaval of adolescence is over, we shift into more familiar patterns.
SONIA ANCOLI-ISRAEL, PhD: People start getting sleepy earlier and earlier and earlier so that when they reach adulthood, they get sleepy at around 11.
ANNOUNCER: At the same time, restful, non-interrupted sleep gets harder to achieve.