Sleep patterns change over the course of our lives. It is common for adolescents to have trouble getting to sleep before the late evening.

Brown University sleep expert Mary  says pressures on the normal biological rhythm of preteens and teens can effectively delay their natural body clocks. "The rate at which that pressure builds up seems to change, and it builds up more slowly. So we think that is the biological system kind of giving permission or enabling the brain to stay awake more easily late into the evening."

This delay is common among teens across cultures. However, teens that spend a lot of time in front of the bright light of computer screens could be fooling their body clocks into thinking it is daytime. Carskadon says many adolescents faced with early morning classes behave much as if they were jet-lagged and fall asleep in school.

But Carskadon says the biological clock is flexible. The mechanism that pushes sleep later can be switched to respond to an earlier bedtime, but not without certain changes. She suggests making bright light available in the morning and minimizing it at night. She says there are also commonsense things like don't drink caffeine or consume energy drinks in the late afternoon or evening that can delay sleep. She says, "Fundamentally make sleep a positive priority. Make a plan for sleep."

Carskadon says within a week, teens can adapt to a new schedule. She says the challenge for adolescents is to accept that sleep is a priority and to stick with a plan that can remedy the situation.