• Teens who don’t get enough sleep are at higher risk for high blood pressure, diabetes, cancer, heart disease, migraines, and obesity, as well as for suicide and adjustment disorder.

Despite all this evidence, however, most people don’t realize that teens—and not just American teens but teens across the globe—are suffering from a huge sleep deficit. When they were babies, they told us, very clearly, when they were exhausted and needed to sleep—they fussed and they wailed and their faces turned red. But now that they’re older, our kids don’t signal their sleep needs so clearly or so noisily— they often show their extreme fatigue in ways we don’t always associate with lack of sleep and do usually attribute to other causes. If they don’t do well on an exam, we think it’s because they didn’t study hard enough. If they’re irritating and unpleasant, we blame it on those raging teenage sex hormones. If they gain weight or their skin breaks out, they’re not eating a well-balanced diet and not getting enough exercise. If they’re unhappy or depressed, well, that’s just teenage angst.

Sexual development, cultural forces, diet, and a strong work ethic, as well as a host of other factors, including family problems, physical and psychological conditions, learning issues, heredity, friends, and the environment, do, of course, greatly affect teen behavior, learning, and health. But now the sleep community knows that lack of sleep also underlies, and has an enormous effect on, all parts of teen life and that the right amount and the right kind of sleep are essential for optimum teen well-being.

The sleep community also knows that there’s a physiological factor that contributes significantly to teenage sleep deprivation: Teens’ brains are actually wired to keep them out of step with most of the world. The secretion of melatonin, a brain hormone that helps cause drowsiness, begins signaling hours later in adolescents than it does in children or adults, turning teens into night owls and making it extremely difficult for them to be awake enough to learn anything during the first few periods of school or to successfully follow a typical adult schedule.

I want to tell you about this critically important finding. And I