The Teenage Brain

A Neuroscientist's Survival Guide to Raising Adolescents and Young Adults

Frances E. Jensen, Amy Ellis Nutt

• Publisher: Collins
• Year: 2015
• Print ISBN:
  9781443406239
• eBook ISBN:
  9781443406246
• Topic: Psychology
• Subtopic: History & Theory in Psychology
• Index: Psychology

In this instant New York Times bestseller, now available in paperback, renowned neurologist Dr. Frances E. Jensen offers a revolutionary look at the brains of teenagers, dispelling myths and "offer[ing] support and a way for parents to understand and relate to their own soon-to-be-adult offspring" (Publishers Weekly). Drawing on her research knowledge and clinical experience, this internationally respected neurologist—and mother of two boys—offers a revolutionary look at the adolescent brain, providing remarkable insights that translate into practical advice for both parents and teenagers.

Driven by the assumption that brain growth was almost complete by the time a child began kindergarten, scientists believed for many years that the adolescent brain was essentially an adult one—only with fewer miles on it. Over the past decade, however, neurology and neuropsychology research has shown that the teen years encompass vitally important physiological and neurological stages of brain development.

Motivated by her experience of parenting two teenage boys, Dr. Jensen gathers what we've discovered about adolescent brain functioning, wiring and capacity and, in this groundbreaking, accessible book, explains how these eye-opening findings not only dispel commonly held myths about the teenage years, but also yield practical suggestions that will help adults and teenagers negotiate the mysterious and magical world of adolescence.

With insights drawn from her years as a parent, clinician and researcher, Dr. Jensen explores adolescent brains at work in learning and multitasking, stress and memory, sleep, addiction and decision-making. The Teenage Brain explains why teenagers are not as resilient to the effects of drugs as we previously thought; reveals how multitasking impacts learning ability and concentration; and examines the consequences of emotionally stressful situations on mental health during and beyond adolescence.

Rigorous yet accessible, warm yet direct, The Teenage Brain sheds light on the brains—and behaviors—of adolescents and young adults, and analyzes this knowledge to share specific ways in which parents, educators and even the legal system can help them navigate their way more smoothly into adulthood in our ever challenging world.

1
Entering the Teen Years

In July 2010 I received an e-mail from the frustrated mother of a nineteen-year-old who had just finished his freshman year of college. The mother had heard me give a talk to parents and teachers in Concord, Massachusetts, about the teenage brain, and her e-mail expressed a wide range of emotions, from sadness to confusion to anger, about the boy, whose behavior had suddenly become downright “weird.”

“My son gets angry easily,” she wrote. “He puts a wall around him so he would not talk. He stays up all night and sleeps all day. He stops doing things he used to enjoy…. He was once charming, intelligent, outgoing. These days, good mood is rare. I thought I did all that hard work to raise him, to send him to a very good college, and it all ended up like this.”

The woman ended her e-mail with a simple question: “How do I help him?”

Letters and e-mails and calls like these are what prompted me to write this book. Nine months after that mother asked how she could help her son, I received a similar e-mail, this time from the mother of an eighteen-year-old girl. Her daughter, who had once seemed so levelheaded, she wrote, had let her grades slip in high school. She became defiant, ran away from home, and was hospitalized for depression. “This year has been difficult for us,” the mother wrote. “Sometimes it seems as if she has been replaced by an alien. It is because of the behavior and the things that she says. She is a completely different person.”

I knew how these women felt. At one time, I felt helpless, too. Because I was newly divorced as my older son, Andrew, entered adolescence, I was painfully aware that my children’s future, as well as their present, was largely up to me. There was no pulling my hair out and saying, “Go talk to your father about it!” When you’re a single parent, the buck stops with you. As parents, we want to open a few doors for our kids—that’s all, really. To gently nudge them in the right direction. During their childhood, everything seems to go pretty much by plan. Our kids learn what’s appropriate and what isn’t, when to go to bed and when to get up in the morning, what not to touch, where not to go. They learn the importance of school, of being polite to their elders, and when they are physically hurt or emotionally wounded, they come to us seeking solace.

So what happens when they reach fourteen, fifteen, or sixteen years old? How is it that the cute, even-tempered, happy, and well-behaved child you’ve known for more than a decade is suddenly someone you don’t know at all?

These are a few of things I say to parents right off the bat: The sense of whiplash you are feeling is not unusual. Your children are changing, and also trying to figure themselves out; their brains and bodies are undergoing extensive reorganization; and their apparent recklessness, rudeness, and cluelessness are not totally their fault! Almost all of this is neurologically, psychologically, and physiologically explainable. As a parent or educator, you need to remind yourself of this daily, often hourly!

Adolescence is a minefield, for sure. It is also a relatively recent “discovery.” The idea of adolescence as a general period of human development has been around for aeons, but as a discrete period between childhood and adulthood it can be traced back only as far as the middle of the twentieth century. In fact the word “teenager,” as a way of describing this distinct stage between the ages of thirteen and nineteen, first appeared in print, and only in passing, in a magazine article in April 1941.

Mostly for economic reasons, children were considered mini-adults well into the nineteenth century. They were needed to sow the fields, milk the cows, and split the firewood. By the time of the American Revolution half the population of the new colonies was under the age of sixteen. If a girl was still single at eighteen, she was considered virtually unmarriageable. Well into the early twentieth century, children over the age of ten, and often children much younger, were capable of most kinds of work, either on the farm or later in city factories—even if they needed boxes to stand on. By 1900, with the Industrial Revolution in full swing, more than two million children were employed in the United States.

Two things in the decades spanning the middle of the twentieth century—the Great Depression and the rise of high schools—not only changed attitudes about the meaning of childhood but also helped to usher in the era of the teenager. With the onset of the Depression after the stock market crash of 1929, child laborers were the first to lose their jobs. The only other place for them was school, which is why by the end of the 1930s, and for the first time in the history of American education, most fourteen- to seventeen-year-olds were enrolled in high school. Even today, according to a 2003 survey by the National Opinion Research Center, Americans regard finishing high school as the number one hallmark of adulthood. (In much of the United Kingdom a teenager is treated as an adult even if he or she does not finish high school, and in England, Scotland, and Wales it is legal not only to leave school at age sixteen but to leave home and live independently as well.) In the 1940s and ‘50s, American youth, most of whom were not responsible for the economic survival of their families, certainly did not seem like adults—at least not until they graduated from high school. They generally lived at home and were dependent on their parents, and as more and more children found themselves going to school beyond the eighth grade, they became a kind of class unto themselves. They looked different from adults, dressed differently, had different interests, even a different vocabulary. In short, they were a new culture. As one anonymous writer said at the time, “Young people became teenagers because we had nothing better for them to do.”

One man foresaw it all more than one hundred years ago. The American psychologist Granville Stanley Hall never used the word “teenager” in his groundbreaking 1904 book about youth culture, but it was clear from the title of his fourteen-hundred-page tome—Adolescence: Its Psychology and Its Relations to Physiology, Anthropology, Sociology, Sex, Crime, Religion and Education—that he regarded the time between childhood and adulthood as a discrete developmental stage. To Hall, who was the first American to earn a PhD in psychology, from Harvard University, and the first president of the American Psychological Association, adolescence was a peculiar time of life, a distinct and separate stage qualitatively different from either childhood or adulthood. Adulthood, he said, was akin to the fully evolved man of reason; childhood a time of savagery; and adolescence a period of wild exuberance, which he described as primitive, or “neoatavistic,” and therefore only slightly more controlled than the absolute anarchy of childhood.

Hall’s suggestion to parents and educators: Adolescents shouldn’t be coddled but rather should be corralled, then indoctrinated with the ideals of public service, discipline, altruism, patriotism, and respect for authority. If Hall was somewhat provincial about how to treat adolescent storm and stress, he was nonetheless a pioneer in suggesting a biological connection between adolescence and puberty and even used language that presaged neuroscientists’ later understanding of the malleability of the brain, or “plasticity.” “Character and personality are taking form, but everything is plastic,” he wrote, referring to pliability, not the man-made product. “Self-feeling and ambition are increased, and every trait and faculty is liable to exaggeration and excess.”

Self-feeling, ambition, exaggeration, and excess—they all helped define “teenager” for the American public in the middle of the twentieth century. The teenager as a kind of cultural phenomenon took off in the post–World War II era—from teenyboppers and bobbysoxers to James Dean in Rebel Without a Cause and Holden Caulfield in The Catcher in the Rye. But while the age of adolescence became more defined and accepted, the demarcation between childhood and adulthood remained—and remains—slippery. As a society, we still carry the vestiges of our centuries-old confusion about when a person should be considered an adult. In most of the United States a person must be between fifteen and seventeen to drive; eighteen to vote, buy cigarettes, and join the military; twenty-one to drink alcohol; and twenty-five to rent a car. The minimum age to be a member of the House of Representatives is twenty-five; to be president of the United States, thirty-five; and the minimum age to be a governor ranges among states from no age restriction at all (six states) to a minimum age of thirty-one (Oklahoma). There is generally no minimum age requirement to testify in most courts, enter into a contract or sue, request emancipation from one’s parents, or seek alcohol or drug treatment. But you must be eighteen to determine your own medical care or write a legally binding will, and in at least thirty-five states those eighteen or younger must have some type of parental involvement before undergoing an abortion. What a lot of mixed messages we give these teenagers, who are not at a stage to weed through the logic (if there is any) behind how society holds them accountable. Very confusing.

So what does being a teenager mean? Man-child, woman-child, quasi-adult? The question is about much more than semantics, philosophy, or even psychology because the repercussions are both serious and practical for parents, educators, and doctors, as well as the criminal justice system, not to mention teens themselves.

Hall, for one, believed adolescence began with the initiation of puberty, and this is why he is considered the founder of the scientific study of adolescence. Although he had no empirical evidence for the connection, Hall knew that understanding the mental, emotional, and physical changes that happen in a child’s transition into adulthood could come only from an understanding of the biological mechanics of puberty.

One of the chief areas of focus in the study of puberty has long been “hormones,” but hormones have gotten a bad rap with parents and educators, who tend to blame them for everything that goes wrong with teenagers. I always thought the expression “raging hormones” made it seem as though these kids had taken a wicked potion or cocktail that made them act with wild disregard for anyone and anything. But we are truly blaming the messenger when we cite hormones as the culprit. Think about it: When your three-year-old has a temper tantrum, do you blame it on raging hormones? Of course not. We know, simply, that three-year-olds haven’t yet figured out how to control themselves.

In some ways, that’s true of teenagers as well. And when it comes to hormones, the most important thing to remember is that the teenage brain is “seeing” these hormones for the first time. Because of that, the brain hasn’t yet figured out how to modulate the body’s response to this new influx of chemicals. It’s a bit like taking that first (and hopefully last!) drag on a cigarette. When you inhale, your face flushes; you feel light-headed and maybe even a bit sick to your stomach.

Scientists now know that the main sex hormones—testosterone, estrogen, and progesterone—trigger physical changes in adolescents such as a deepening of the voice and the growth of facial hair in boys and the development of breasts and the beginning of menstruation in girls. These sex hormones are present in both sexes throughout childhood. With the onset of puberty, however, the concentrations of these chemicals change dramatically. In girls, estrogen and progesterone will fluctuate with the menstrual cycle. Because both hormones are linked to chemicals in the brain that control mood, a happy, laughing fourteen-year-old can have an emotional meltdown in the time it takes her to close her bedroom door. With boys, testosterone finds particularly friendly receptors in the amygdala, the structure in the brain that controls the fight-or-flight response—that is, aggression or fear. Before leaving adolescence behind, a boy can have thirty times as much testosterone in his body as he had before puberty began.

Sex hormones are particularly active in the limbic system, which is the emotional center of the brain. That explains in part why adolescents not only are emotionally volatile but may even seek out emotionally charged experiences—everything from a book that makes her sob to a roller coaster that makes him scream. This double whammy—a jacked-up, stimulus-seeking brain not yet fully capable of making mature decisions—hits teens pretty hard, and the consequences to them, and their families, can sometimes be catastrophic.

While scientists have long known how hormones work, only in the past five years have they been able to figure out why they work the way they do. Because sex hormones are present at birth, they essentially hibernate for more than a decade. What, then, triggers them to begin puberty? A few years ago, researchers discovered that puberty is initiated by what appears to be a game of hormonal dominoes, which begins with a gene producing a single protein, named kisspeptin, in the hypothalamus, the part of the brain that regulates metabolism. When that protein connects with, or “kisses,” receptors on another gene, it eventually triggers the pituitary gland to release its storage of hormones. Those surges of testosterone, estrogen, and progesterone in turn activate the testes and ovaries.

After sex hormones were discovered, for the rest of the twentieth century they became the dominant theory of, and favorite explanation for, adolescent behavior. The problem with this theory is that teenagers don’t have higher hormone levels than young adults—they just react differently to hormones. For instance, adolescence is a time of increased response to stress, which may in part be why anxiety disorders, including panic disorder, typically arise during puberty. Teens simply don’t have the same tolerance for stress that we see in adults. Teens are much more likely to exhibit stress-induced illnesses and physical problems, such as colds, headaches, and upset stomachs. There is also an epidemic of symptoms ranging from nail biting to eating disorders that are commonplace in today’s teens. We have a tsunami of input coming at teens from home, school, peers, and, last but not least, the media and Internet that is unprecedented in the history of mankind. Why are adults less susceptible to the effect of all this stimulation? In 2007, researchers at the State University of New York (SUNY) Downstate Medical Center reported that the hormone tetrahydropregnanolone (THP), usually released in response to stress to modulate anxiety, has a reverse effect in adolescents, raising anxiety instead of tamping it down. In an adult, this stress hormone acts like a tranquilizer in the brain and produces a calming effect about a half hour after the anxiety-producing event. In adolescent mice, THP is ineffective in inhibiting anxiety. So anxiety begets anxiety even more so in teens. There is real biology behind that.

In order to truly understand why teenagers are moody, impulsive, and bored; why they act out, talk back, and don’t pay attention; why drugs and alcohol are so dangerous for them; and why they make poor decisions about drinking, driving, sex—you name it—we have to look at their brain circuits for answers. The elevated secretion of sex hormones is the biological marker of puberty, the physiological transformation of a child into a sexually mature human being, though not yet a true “adult.”

While hormones can explain some of what is going on, there is much more at play in the teenage brain, where new connections between brain areas are being built and many chemicals, especially neurotransmitters, the brain’s “messengers,” are in flux. This is why adolescence is a time of true wonder. Because of the flexibility and growth of the brain, adolescents have a window of opportunity with an increased capacity for remarkable accomplishments. But flexibility, growth, and exuberance are a double-edged sword because an “open” and excitable brain also can be adversely affected by stress, drugs, chemical substances, and any number of changes in the environment. And because of an adolescent’s often overactive brain, those influences can result in problems dramatically more serious than they are for adults.

2
Building a Brain

The human body is amazing, the way it neatly tucks all these complex organs into this finite space and connects them into one smoothly functioning system. Even the average human brain is said by many scientists to be the most complex object in the universe. A baby brain is not just a small adult brain, and brain growth, unlike the growth of most other organs in the body, is not simply a process of getting larger. The brain changes as it grows, going through special stages that take advantage of the childhood years and the protection of the family, then, toward the end of the teen years, the surge toward independence. Childhood and teen brains are “impressionable,” and for good reason, too. Just as baby chicks can imprint on the mother hen, human children and teens can “imprint” on experiences they have, and these can influence what they choose to do as adults.

Such was the case with me. I “imprinted” on neuroscience and medicine pretty early on. My experiences cultivated in me a curiosity that I found irresistible, sustaining me from my high school years through medical school and graduate research, and to this very day. I grew up the oldest of three children in a comfortable family home in Connecticut, just forty minutes from Manhattan. I happened to live in Greenwich, which even back then was the home of actors, authors, musicians, politicians, bankers, and the independently wealthy. The actress Glenn Close was born there, President George H. W. Bush grew up there, and the great bandleader Tommy Dorsey died there.

My parents were from England; they had immigrated after World War II, and my dad came over after medical school in London to do his urological surgery residency at Columbia. To them, Greenwich seemed a great place to settle within commuting distance of New York City. It was a matter of convenience, and they were pretty oblivious to the celebrity status of the town. Perhaps because of my father, I was open-minded about learning math and science. For me a major “imprinting” moment that propelled me in the direction of medicine was a ninth-grade biology class at Greenwich Academy. The best part to me, memorable in fact, was when we each got a fetal pig to dissect. While many of my classmates slumped in their seats at the proposition of slicing up these small mammals, some rushing to the girls’ washrooms with waves of nausea, a few of us jumped into the task at hand. It was one of those defining moments. The scientists had separated from those destined to be the writers, lawyers, and businesspeople of the future.

Injected with latex, the pigs’ veins and arteries visibly popped out with their colorful hues of blue and red. I’m a very visual person; I also like thinking in three dimensions. That visual-spatial ability comes in handy with neurology and neuroscience. The brain is a three-dimensional structure with connections between brain areas going in every direction. It helps to be able to mentally map these connections when one is trying to determine where a stroke or brain injury is located in a patient presenting with a combination of neurological problems—definitely a plus for a neurologist. Actually, that’s how the minds of most neurologists and neuroscientists work. We’re a breed that tends to love to look for patterns in things. I’ve never met a jigsaw puzzle, in fact, that I didn’t like. My attraction to neuroscience in high school and college began at a time before CT scans and MRIs, when a doctor had to imagine where the problem was inside the brain of a patient by picturing the organ three-dimensionally. I’m good at that. I like being a neurological detective, and as far as I’m concerned, neuroscience and neurology turned out to be the perfect profession for me to make use of those visuospatial skills.

If the human brain is very much a puzzle, then the teenage brain is a puzzle awaiting completion. Being able to see where those brain pieces fit is part of my job as a neurologist, and I decided to apply this to a better understanding of the teen brain. That’s also why I’m writing this book: to help you understand not only what the teen brain is but also what it is not, and what it is still in the process of becoming. Among all the organs of the human body, the brain is the most incomplete structure at birth, ju...

Table of contents

• Dedication
• Epigraph
• Contents
• List of Illustrations
• Introduction: Being Teen
• 1 Entering the Teen Years
• 2 Building a Brain
• 3 Under the Microscope
• 4 Learning : A Job for the Teen Brain
• 5 Sleep
• 6 Taking Risks
• 7 Tobacco
• 8 Alcohol
• 9 Pot
• 10 Hard-Core Drugs
• 11 Stress
• 12 Mental Illness
• 13 The Digital Invasion of the Teenage Brain
• 14 Gender Matters
• 15 Sports and Concussions
• 16 Crime and Punishment
• 17 Beyond Adolescence: It’s Not Over Yet
• Postscript: Final Thoughts
• Acknowledgments
• Glossary
• Notes
• Selected Bibliography
• Resources
• About the Authors
• Advance Praise for THE TEENAGE BRAIN
• ALSO BY AMY ELLIS NUTT
• Credits
• Copyright
• About the Publisher