Contrast between the sleep-wake schedule of a prepubertal child and that of an adolescent. Specifically note the later onset of alertness, later dim light melatonin onset signaling the initiation of processes leading to sleep, and later sleep onset time for the teen.

to understand why it’s so incredibly difficult to wake a sleeping teen at 6:00 a.m., think how hard it would be if you had to get up for work at 3:00 a.m.—it’s pretty much equivalent.

For sleep to occur, the clock-dependent alertness that’s generated by Process C needs to be turned off by melatonin. For children and adults who go to bed at 10:00 p.m., melatonin secretion, or dim light melatonin onset, typically begins about six hours earlier, around 4:00 p.m. But in adolescents melatonin onset may not occur until hours later.

Still another problem is the length of the day. Children’s and adults’ body clocks follow a day that is approximately 24.3 hours long, but— you guessed it—the adolescent body clock beats to a different drum. Teens’ biological processes work to a slightly longer day, one that can

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