excessive sleepiness in adolescents, which can impair daytime functioning. First, daytime sleepiness can increase during adolescence, even when teens’ schedules allow for optimal amounts of sleep (Carskadon, Vieri, & Acebo, 1993). Second, most adolescents undergo a sleep phase delay, which means a tendency toward later times for both falling asleep and waking up. Research shows the typical adolescent’s natural time to fall asleep may be 11 pm or later; because of this change in their internal clocks, teens may feel wide awake at bedtime, even when they are exhausted (Wolfson & Carskadon, 1998). This leads to sleep deprivation in many teens who must wake up early for school, and thus do not get the 8 1/2 - 9 1/4 hours of sleep that they need. It also causes irregular sleep patterns that can hurt the quality of sleep, since the weekend sleep schedule often ends up being much different from the weekday schedule as teens try to catch up on lost sleep (Dahl & Carskadon, 1995).
Since the 1970s, there has been a growing awareness of the changes in sleep patterns as children transition to adolescence. In a study at a summer sleep camp at Stanford during the 1970s, boys and girls who enrolled at 10-12 years of age were monitored every year for 5-6 years. While researchers had thought older children would need less sleep during the 10 hour nocturnal window they were given, from 10 pm to 8 am, they found that regardless of age, the children all slept about 9 1/4 of the 10 hours. As they progressed through adolescence, participants continued to get the same amount of sleep, but they no longer woke spontaneously before the end of the sleep window at 8 am (Carskadon et al., 1979). In addition, when the Multiple Sleep Latency Test (MSLT)—given at designated periods throughout the day to determine the speed of falling asleep, to measure sleepiness—was given to the adolescents, they showed more alertness at 8 pm than earlier in the day, and even greater alertness at 10 pm. Also, at midpuberty,