Dahl suspects, and preliminary results from experiments concur, that adolescents short on sleep are impaired in their ability to make these adult calculations and are less likely to suppress the childlike emotions they are beginning to outgrow.
"It's dangerous to generalize," Dahl said, "but there are large numbers of teens for whom a simple lack of sleep may really tip the balance for having emotional difficulties."
'Participants Instead of Zombies'
For adolescents, whose delayed melatonin surge means that critical sleep is often still going on at 7 a.m., findings like these suggest that early school starting times may be resulting in grogginess and lack of attention in class, poor performance on exams and increased odds of behavioral or disciplinary problems.
"Kids are waking up and going to school at a time when their brains are still in the nighttime mode," Carskadon said. "Even in second period, they are not ready to learn, not ready to be engaged in education."
That's why school officials in Edina last year decided to make an unprecedented bid for wakefulness by having its 1,350 students start classes at 8:30 a.m. instead of 7:20. So far, said Wahlstrom, everything suggests the experiment is working.
"Previously, 20% of these kids were sleeping during the first hour of school," said Wahlstrom, a former teacher, elementary-school principal and school administrator. "Now none are. They are participants instead of zombies."
The extra rest seemed to have a ripple effect. According to Wahlstrom, administrators got fewer referrals for discipline problems under the new schedule, and the number of students reporting that they were depressed or ill dropped dramatically. "The nurse can't get over the reduction in the referrals to her office in the mornings," she said.
The ultimate test, of course, is academic performance, and here the new schedule also seems to be at least a partial success. Student scores were higher last year than in previous years for grades 11 and 12, although there was no noticeable difference in younger students' grades.
"All the stuff we're finding in Edina is bearing out the findings reported initially in [sleep lab] studies," Wahlstrom said.
Last year Wahlstrom conducted research to see what it would take to get a larger region of Minnesota, encompassing Edina and 16 other school districts, to make their starting times later.
She and her colleagues interviewed parents, teachers and students; they spoke with transportation and busing directors; they sat down with athletic coaches, who wanted to make sure the change wouldn't interfere with team practices or games; they spoke with food service and meal coordinators and with advisors for various extracurricular activities.
It was a massively complicated job. "I was one of the most sleep-deprived researchers you ever met," Wahlstrom said. But the results were encouraging. "We showed that . . . there's no inherent reason why it can't be done."
One of those 16 districts was changing its schedule this fall, with a modest but potentially helpful delay of about a half-hour for its 2,148 students in grades 10 to 12. Another district will offer a two-tiered system in which the 1,485 students in those grades can choose to start at either 7:30 a.m. or 8:30. (Interestingly, about one-third of those students have opted for the earlier slot, corresponding almost exactly with research findings that about 30% of people are natural "larks.")
In the biggest and boldest move of all, Minneapolis city schools, which were not part of the survey, will delay their opening time 45 minutes to 8:30 a.m. this year for its students in grades 10 to 12.
"That will really be interesting," Wahlstrom said. "It's a very urban school district with all the usual urban problems" of poor academic performance, behavioral problems and after-school crime. "We hope this will increase academic achievement and, with kids spending a little more time in school in the afternoon, maybe lead to less trouble in the neighborhoods."
Getting to Bed Early Is Key
If follow-up studies indicate that later starting times are indeed helping students, then other districts may follow. But what can teens and parents do for now if the school bus is rolling up at 6:30 a.m. or even earlier, nipping REM sleep in the bud and in many cases making breakfast a weekend luxury?
Most important, experts said, is getting youngsters to bed as early as is reasonably possible. Melatonin timing may make it difficult for adolescents to fall asleep before 11 p.m., but if they go to bed before then, perhaps with a good book in hand, then at least they'll nod off at the first natural opportunity.
Without strict bedtimes, experts said, adolescents may get fooled by the false sense of wakefulness that often arises between 8 and 10 p.m.