Most teens don't get enough sleep, usually because their schedules are overloaded or they spend too much time texting or chatting with friends until the morning. Other teens try to go to sleep early, but instead of getting much-needed rest, they lie awake for hours.
Over time, nights of missed sleep can build into a sleep deficit. Teens with a sleep deficit can't concentrate, study, or work effectively. They also can have emotional problems, like depression.