Schools Are Starting Earlier But Sleepy Teens Need Just The Opposite

Teens have fundamentally different circadian rhythms than the rest of us

Photo Illustration: Tara Jacoby
Apr 13, 2017 at 8:03 AM ET

Teenagers are supposed to get nine to 10 hours of sleep a night, but anyone who remembers high school has a pretty good idea just how rarely students actually get that much shut-eye. One longtime sleep researcher says there’s no easy way to fix the problem when schools start so early in the day.

Previous studies have shown serious consequences to a lack of rest, including sleepiness-related car accidents and increased risk of obesity and depression. Even just nodding off in class can have a serious impact when you think about all the potentially millions of kids missing out on a chunk of their education. So the question becomes what’s causing all this teen drowsiness.

As kids grow up, many start doing things that will keep them up later, like drinking caffeine and spending more time watching TV or using the computer. But Brown University sleep expert Mary Carskadon argues the real causes run deeper than that. Her decades-long research suggests our circadian rhythms move to later at night as we enter our teen years, meaning we are naturally inclined to stay up later and not wake until later in the morning.

It’s that second part especially that Carskadon has focused on. Her previous studies have suggested teens actually need just as much sleep as younger kids — if you let an adolescent sleep until they wake up naturally, it will likely be the same 10 or more hours that a little kid gets. The problem is teen sleep has a natural enemy in the early start times for most high school. One of her studies took 10th graders who got about seven hours of sleep and woke up for a 7:20 a.m. school start time and let them go back to sleep at 8:30. About half almost instantly fell back into deep REM sleep, suggesting just how desperately they needed to catch up.

The most obvious solution then is to have high schools start later in the day, adjusting schedules to reflect teens’ natural sleep habits. Carskadon’s home state of Rhode Island is considering a law that would move school start times back to 8:30 a.m., meaning teens who got to bed around 10 p.m. should be able to get enough sleep. Again, some high schoolers may scoff at the idea of a regular 10 p.m. bedtime, but even that hour’s difference could help fight what Carskadon calls “social jet lag” — the basic reality teens are forced to live on a daily schedule that’s utterly mismatched with their bodies’ natural sense of time.