INSIDE THE TEEN BRAIN
photo of mary carskadoninterview: Mary Carskadon

Are teens getting enough sleep?

Most teens in North America are absolutely not getting enough sleep.

How much sleep are they getting?

In our surveys and in our field studies, we're seeing that, on average, teens are getting about seven-and-a-half hours a night's sleep on school nights. And actually a quarter of the kids are getting six-and-a-half hours or less sleep on school nights. So when you put that in the context of what they need to be optimally alert, which is nine-and-a-quarter hours of sleep, it's clear that they're building huge, huge sleep debts, night after night after night.

And how does lack of sleep affect them?

Well, the teenagers are really put in a kind of a gray cloud when they aren't having enough sleep. It affects both their mood and their ability to think and their ability to perform and react appropriately. So we have kids out there who struggle to stay awake while driving, who could do better at sports if they could react more quickly, who are feeling blue and having trouble getting along with the adults in their environment, and also who are struggling to learn in the classroom. Sleep learning isn't really something that works. And so when you go out and see a classroom of teens sleeping, they're not learning.

What do you see in those first hours of the school day in America?

Well, the problem is worst for teenagers in the morning. ... Fundamentally, the issue is they're not filling up their tank at night, and so they're starting the day with an empty tank. What's interesting is there's another part of their brain that's the biological timing system, or the circadian clock, that actually helps to prop them up at the end of the day. But when they start the day with the empty tank and there's no biological clock helping them in the morning, they really should be home in bed sleeping, not sleeping in the classroom.

And what do you see when you look at children in the classroom, grades nine and ten, in those first periods?

What you see in the classroom is a sea of sleepy faces and drool on their notebooks and so forth. When we bring those kids into the laboratory, what we see is a phenomenon that's of a lot of concern for us. They start to look as if they have a major sleep disorder -- narcolepsy. So we bring them into the lab. We get them all hooked up and we do these short naps at intervals across the day.

And in the morning time, these kids fall asleep like that and half of them will go directly into REM sleep; and that's exactly what patients with narcolepsy do. Now, these adolescents don't have narcolepsy. But they're living under circumstances that actually make them look just as if they have a major sleep disorder.



Carskadon is a professor of psychiatry and human behavior at Brown University and director of chronobiology and sleep research at E.P. Bradley Hospital in Providence, R.I. Her research focuses on the interrelation between the circadian timing system and sleep/wake patterns of children and adolescents. Her work has highlighted the consequences of insufficient sleep in adolescents, as well as concerns about early school starting times.

What is narcolepsy?

Narcolepsy is a major sleep disorder that involves a defect in a neurochemical pathway in the brain. The result of that is that people are excessively sleepy, and they have disorders of REM sleep in particular.

And this is how you would describe a good portion of teenagers?

Well, in a sample that we looked at, we could describe half of them like that.

That sounds risky to me. Is that risky to you as a researcher?

That was the finding that got my attention and really made me think that, you know, these early school start times -- and this was in a sample of kids who were going to school, I think, first bell was 7:20 in the morning. They just weren't adapting to it. They weren't accommodating to it, and it was producing this awful effect.

When you go out and see a classroom of teens sleeping, they're not learning.

Is it dangerous? I think it is, particularly with so many teenagers driving themselves to school in the morning. They'll do anything to get a few more minutes of sleep in the morning, so they don't take the bus if they possibly can't. As soon as they get a car, they're in it, and they use it to get to school and to get that extra 10, 15, 20 minutes of sleep in the morning. So here are these sleepy teens on the road when they're maximally impaired.

So it's risky for driving. Are there other risks to it?

We think there are other risks, and we don't have all the data to know. But it's clear that one of the big risks seems to be the effect on mood and the ability for teenagers to regulate mood. We see across the country a new wave -- if not epidemic -- of depression in teenagers. We don't know yet one for one, but there's this sneaking suspicion out there that one of the things that leads into depression is this hyper-somnolence and this sort of change in overall mood and affect that some of these teenagers undergo. And I think if you're vulnerable to that pathway to depression, that is a serious risk of this huge amount of sleep debt in teenagers.

Why is this happening at this particular time?

That's an interesting question: Why is it happening now? There seems to have been a change that's happened kind of gradually over time in how schools are regulating their starting times. When you combine that with kind of the social zeitgeist now with all of the things that teenagers have available to them that occur late at night, from televisions and telephones and computers in the bedrooms to jobs that they take that go late into the night, their sleep has been shoved into an ever-narrowing window. So it's partly societal, cultural, and it's partly this sort of demand of the adult world. Then we have to fit in the kids' biology into that system that we're left with. The puzzle isn't all working out. ...

What we are finding also is a lot of kids just [don't go to] school. So all of a sudden, the day will come when they just can't marshal their resources, as slim as they are in the morning, to get up for school. They just say they're not going to school today. More and more, we're seeing kids not [missing] school because they're sick; it's just they're too tired. ...

Is the teens' biology different from younger children and adults?

What we know about teenagers is they still need as much sleep as they did when they were pre-teens. So the need for sleep, in spite of our sort of common notions that the older you are the less sleep you need, that doesn't seem to be true across that span from, say, age 8, 9, 10 to age 20, and we don't know quite beyond that. So that's point number one.

And then within that time frame, it appears as if there are changes in the way the brain is regulating sleep and the timing of sleep. So one of the things that our research is examining is this delay, or later bed times, later wake-up times that occur in teenagers, and to what extent the brain is producing that kind of delay. So that's the biology we think is changing during adolescent development. ...

What can be done about [this problem of teens not getting enough sleep]?

This is a bigger problem than just adolescence. Our society in general has sort of put sleep in the back seat, doesn't think about sleep anymore, and doesn't really understand or acknowledge the importance of sleep. So for me, sort of the battle is to have a more generally acknowledged positive priority on sleep. I think we need to be teaching about sleep.

It's so interesting to me that you can go into classrooms with tiny little kids and you can learn the food pyramid and you can learn the importance of not smoking and of wearing helmets and so forth, and not ever hear word one about sleep. Furthermore, you can see that all the way through school, into college, into medical school... The amount of information that's being taught in formal curricula about sleep is virtually nil. So I think that's going to have a big impact.

I think that adolescents in particular need to know about sleep. Their parents, teachers, school administrators, the school nurses need to know. And maybe we need to start reexamining the issue of the school starting time, and really turn back the clock a little bit to give these kids a break.


When school districts have bumped up their start time, what has been the result of that?

The few school districts that have made starting time later for teenagers, some of them are reporting very positive response, both from the teachers, parents, the kids. It's just they talk about it as being a tangibly happier environment. There is a group in Minneapolis that's tracking some schools in that area of the country who've made the change, and they're finding mixed results.

It's interesting. My interpretation of some of their most recent results [is that] they're not really seeing big bursts of higher grades in school. They're seeing more kids in the classroom. So fewer of these kids are not being able to get up and make it to school. That means you have a bigger sample altogether, and I think that's affecting some of their results on grades.

But there have been some other districts where it's just sort of blown up in the face of the schools when they've tried to delay. If the schools don't do some education in advance of making this change, it can negative outcomes. ... Parents have structures, daycare and childcare for the little ones being provided by the older ones. It just can get out of control unless there's some groundwork laid, some preparation. And again, we come back to this issue of education.

In your writing, you talk about a "forbidden zone" of sleep. What do you mean by that?

It's interesting. When we talk about how sleep is controlled by the brain, we really are talking about two systems. One is the system that fills the tank at night, and the other is the biological clock system. It sets up a sort of cycle of when it's easy to fall asleep and when it's hard to fall asleep. Those times when it's hard to fall asleep we call "forbidden zones" for sleep.

We see in many adolescents that this forbidden zone is in the evening hours. So they actually feel great at night and, for many of them, that makes it harder for them to even consider trying to go to bed earlier. So they'll say goodnight to Mom and Dad and they'll go into their rooms and read or play video games or talk on the phone. And they're perfectly content and happy doing that, because they're also at a phase where it's easy for them to become aroused and stimulated by these activities. So it really does turn into a Catch--22. When people just say, "Well, all they have to do is go to bed earlier," well, they really can't go to sleep earlier necessarily.

What can be done on an individual basis?

Kids who are struggling with this need to assess what's going on in their lives and what changes and what is important and how to do it. You can't just all of a sudden turn back the clock and make a big change overnight. The brain and the body and the timing systems don't work that way. So gradual changes can be made.

Our brain learns when it's night and when it should be sleeping by the information it gets through our eyes, and that's light. It seems as if teenagers limit the amount of light they get at nighttime and maximize the amount of light they get in the morning hours. That helps to turn the clock back a little bit earlier for them and enables them to go to sleep earlier. Some teenagers might benefit from an after-school nap; that actually can help a lot. But it doesn't help this morning empty tank. A nap in the afternoon doesn't fill the morning's tank.

What about this teenage pattern of going to sleep quite late, getting up early in the morning for the week, and then sleeping very late on the weekends? Are they catching up?

We get "binge sleeping," as we call it. It actually does help to catch up, and it helps to replenish the stores of sleep. But it has a negative impact, because it's giving the brain a different message about when nighttime is. So kids who sleep, say, 11 p.m. to 6 a.m. on school days, and then on weekends stay up until 2 a.m. or 3 a.m. and sleep until 2 p.m. or 3 p.m., they're replenishing their sleep stores.

But now they're telling the brain, "Well, nighttime is really 2 a.m. to 2 p.m." That's just a terrible message for the brain to start having on Monday morning, when it's trying to get back on the school schedule. So again, we're sort of in this very tough situation of what you do under those circumstances.

What I think would help is if teenagers could do whatever they can on school nights to get eight-and-a-half hours in bed, sleeping. They're still going to get a sleep debt, but it's not going to be this massive sleep debt. And then on weekend nights, if they sleep in and get nine, ten, ten-and-a-half hours, it's not giving the clock this huge wrong messages, and it is enough to replenish the sleep storage depot. ...

We saw an experiment where you put on lights at certain times of the night that the light would not normally come on. Can you explain to us what you were doing with that?

We're trying to find out if one of the things that may be changing in the brains of adolescents is when the clock in their brain is sensitive to light. What we think may be happening, and we have a little bit of evidence now, is that the little kids, before they reach puberty, are very sensitive to light in the morning. And that's why they can fall asleep easily at night and they wake up in the morning with joy in their hearts and songs on their lips.

The older kids, we think, may be less sensitive to light in the morning and more sensitive to light in the evening. And that may be what's pushing their clocks to a later timing system, because evening light is a signal for the clock that, "Oh, it's not night yet, so we better move later." So when we're doing those tests. That's the question that we're trying to answer.

And you answer it by testing melatonin levels?

Right. ... Melatonin is the brain's hormone of darkness, so the brain turns on melatonin production when it's the nighttime of the brain. You can shut that off by shining a light through the eyes. And the question is, how much light does it take to shut down melatonin? That gives us some sense of how the brain's clock is reacting to light. ...

home + introduction + from zzzs to a's + work in progress + seem like aliens? + science
discussion + producer's chat + interviews + video excerpt + watch online
tapes & transcripts + press reaction + credits + privacy policy

FRONTLINE + wgbh + pbs online

some photographs copyright ©2002 photodisc. all rights reserved
web site copyright 1995-2014 WGBH educational foundation

SUPPORT PROVIDED BY

RECENT STORIES

FRONTLINE on

ShopPBS