There are more than 29 million teenagers in this country -- 29 million fertile, creative, impressionable minds that each and every day face the daunting array of challenges called adolescence.
Adolescence has been described as a busy time for the human brain. It's a time of transition, as the brain, like the rest of the body, physically eases into adulthood. And in the process, the brain's gray matter absorbs an explosion of new external stimuli -- stimuli uniquely attached to the teenage years. High school, peer pressure, sexuality. The list goes on. And as it does, the brain is challenged. In most cases, it thrives. Sometimes it does not.
Over the next hour, you'll be hearing some of the stories about science and the teenage brain. They are stories, first and foremost, about teenagers themselves. But they are also stories about scientists who are looking inside the teenage brain in order to better understand how and why young people develop and behave the way they do.
Narrator: You're listening to a special one-hour edition of "Gray Matters: The Teenage Brain" - from PRI, Public Radio International...
The lives of American teenagers have never been more full. With classes during the day, extracurricular activities or jobs that run into the night, then homework -- high school students are usually the last to bed and the first to rise. The first casualty of these rigorous schedules is sleep. In fact, some experts say there's a crisis of sleep deprivation among adolescents. Researchers say part of the problem is a change in the brain that occurs in adolescents that causes teens to fall asleep later at night.
Chris Roberts reports on what researchers have learned about the sleep patterns of adolescents, and what one school district in Minnesota has done to accommodate their sleep needs.
(sound of mother waking her son...)
It's six o'clock on a September morning, and Colleen Feigee is trying to rouse her 14-year-old son Evan from a deep sleep.
(Sound again of son resisting mom's attempts to wake him.)
This mother-son wake-up call has been a school day ritual since Evan was a child. Feigee recalls when Evan was younger, he would rise immediately with a chirpy disposition.
Feigee: "But now, it's not the same. I mean he's not as happy in the morning when he has to get up and go to school. Not that he doesn't like school, it's just that he's still really tired."
(Alarm clock sounds)
An hour later, the short blast of an alarm clock reminds Evan's 17-year-old brother Gregor that he has a little more than a half-hour to get to his 7:30 class. As an honor student, athlete, and high school men's chorus member, Gregor's days are often crammed with activities and obligations. He says sometimes he feels like a zombie, fighting off sleep in school and ready for bed after dinner. But the sleep doesn't come. So he waits.
Gregor: "I will hit the bed at like 10:30.... I can't fall asleep, I'm just awake...and I don't know why it is, it's like I'm physically exhausted, but I'm not tired enough to fall asleep. I end up just lying in bed for 45-minutes and then I doze because my body's ready to, and that's just the way it is."
For years people have assumed that teenagers went to bed at increasingly later times and slept in later because of psychological and social changes associated with adolescence. Teens do feel pressure to stay up later, whether because they need to study, or because their social lives are more active, or maybe because they're trying to assert their autonomy. But scientists now believe kids more readily give in to these factors because of changes in the brain's biological timing system that governs their sleep and wakefulness. Mark Mahowald, Professor of Neurology at the University of Minnesota Medical School and Director of the Minnesota Regional Sleep Disorder Center, explains.
Mahowald: "Older adolescents have a shift in the timing of their biological clock, so they're unable to fall asleep as early as they did in jr. high, and should be sleeping later to awaken rested and restored. Despite these scientific facts, virtually all schools in this country begin with senior high school students going first, which is in essence sending them to school in the last third of their sleep period."
Most of the research on sleep and teens that Mahowald refers to was conducted by Mary Carskadon. Carskadon is Professor of Psychiatry at Brown University and Director of the Biological Rhythms and Sleep Research Laboratory at Bradley Hospital in Providence, Rhode Island. She's devised numerous studies and surveys of middle school and high school students that have led to a new understanding of the sleep patterns of adolescents and how biological processes cause a delay in their sleep cycle. In the laboratory, Carskadon has focused her research on the circadian timing system or biological clock of teenagers.
Carskadon: "The biological clock is actually a set of neurons in the brain, and these neurons are sending signals out to every part of your body that control virtually all of the body's internal processes and their timing, and one of the things the biological clock is involved in controlling is sleep."
Carskadon says the way to measure when the biological clock, or circadian timing system tells the body it's time for sleep, is to monitor when the body secretes a hormone called melatonin. Melatonin production is prompted by the light dark cycle. It occurs during nighttime hours and is detectable in saliva. In a study of teenagers in various stages of adolescence, Carskadon found that the further along the teens were in puberty, the later at night their melatonin was secreted.
Carskadon: "When you think about it in sort of black and white terms...when the melatonin secretary phase is later, which means the circadian timing system is later, you really can't just say to yourself, well I'm going to change now and I'm going to go to sleep at 9:00 instead of 11:00, because the brain is not ready for sleep."
Carskadon says scientists still don't know why the delay occurs, or why the sleep cycle shifts back to a more normal schedule in adulthood. Researchers advise parents not to go out and buy melatonin at the drug store to treat their kids.
Studies indicate teenagers need nine and a quarter hours of sleep a night to be adequately rested the next day. If a student goes to bed at 11:30 or midnight because a delay in their sleep cycle, and has to wake up at six or earlier to get to school at 7:15 or 7:30, they accumulate a significant sleep debt by the end of the week. In one study, Carskadon examined the sleep habits of 25 ninth graders who started school at 8:25, and looked at them again when the students moved on to tenth grade with a start time of 7:20, more than an hour earlier. She says half of the students exhibited signs of narcolepsy, an affliction that causes the sufferer to spontaneously fall asleep against their will.
Carskadon: "So you can imagine A) where their brains are at 8:30 in the morning, and B) how much effort a teacher has to pour into the system to get the attention of these brains that really should be home on the pillow in bed."
(Sound of Edina High students and fade under)
In the Minneapolis suburb of Edina, high school students now have an extra hour of sleep. Two years ago, school officials decided to move back the start time from 7:25 to 8:30. Despite some initial headaches in reconfiguring the bus and athletic schedules, officials say the move has been a success. Health teacher Pacy Erk says the change has caused a dramatic improvement in the demeanor and alertness of her first hour students.
Erk: "I now have a class that's very lively.... they interact with me very positively, because students are more awake."
Before Edina High went to a later start time, advanced placement history teacher Lonnie Skretner says her first hour class was consistently outperformed by her sixth hour class. That's no longer the case.
Skretner: "The year we made the change to a later start time, I had an advanced placement class first hour, and it was an enormous difference. They were my best class of the day."
(Hallway sound fades)
University of Minnesota researchers have conducted formal surveys in Edina with students, parents and counselors that reinforce the teachers' point of view. They're now investigating whether the later start time has resulted in higher academic achievement among students. Sleep experts say there are also health issues to consider when adolescents are sleep deprived. Sleepy teens are more inclined to use stimulant drugs or nicotine for a boost and, according to the National Sleep Foundation in Washington, young people are the largest at-risk group for drowsy driving and fall-asleep car accidents. But experts such as the University of Minnesota's Mark Mahowald warn that changing the school start time won't truly be effective unless it's accompanied by a reevaluation of the frantic pace of teenagers' lives.
Mahowald: "Our children are programmed from before school starts in the morning, often until midnight. Then they're supposed to get their homework done, then they're supposed to go to school earlier then they would like to wake up. More and more schools on the weekends are having the students participate in community service activities which I think are very good, the problem is many of them are starting at seven or eight on Saturday morning, which would be the logical catch-up sleep time for the accumulated sleep deprivation. So we are being very disrespectful to the sleep needs of our adolescents."
Despite Edina's success with the later start time, and all the research on the adolescent sleep delay, the vast majority of school districts across the country are hesitant to make the shift. Many districts contend one of the primary barriers is the difficulty in changing bus schedules. But sleep expert mark Mahowald says if the primary mission of schools is education, then districts are failing, if they're sending kids to school too tired to learn.