Perspective
Betwixt and Between
A New View of the Adolescent Brain
By David Walsh, Ph.D.
Neuroimaging has shown that the prefrontal cortex is not fully developed in teens.
Slamming doors, defiant language, missed curfews, and inexplicably bad decisions: Adolescents have a reputation for this sort of thing. No matter how mild a child is when he’s very young or how sensible a person becomes once she reaches adulthood, the chances are good that just about all kids, more than once during the teen years, will make their parents feel as if their sanity is hanging by a thread.
For years, the explanations for this phenomenon were not very sophisticated and far from scientific. Even the most complex psychological demystifications of teen behavior depended on a sense that, essentially, it’s just a part of growing up and, therefore, something to be endured. Teenagers just acted that way because, well, that’s the way they acted. Unable to know exactly what was going on in those carefully coiffed heads, the best we could do was anticipate and react to the trials of adolescence.
Now, thanks to a recent revolution in neuroscientific imaging technology, we can see the adolescent brain at work. And for the first time, we can begin to say why teenagers act the way they do. What’s more, we can explain why younger and younger kids, the so-called “tweens,” seem to be acting out like their older siblings. It’s not because tweens are copying the older kids, and it’s certainly not because they’re bad kids. In fact, the behaviors we might call defiant or irresponsible often aren’t intended to be perceived that way. In some cases, adolescents can’t help what they’re doing. That’s because the adolescent, whose brain is in the midst of vast developmental changes, doesn’t always know how to act.
A New Sense of Adolescence
The word “adolescence” used to be synonymous with the teenage years. Increasingly, however, adolescence, which begins with the onset of puberty, stretches from the preteen or tween years until well into the early 20s. No one really knows why adolescence is beginning earlier than it did in the past. Some theories cite nutrition or food additives. Others point to exposure to sexual images in the media. Whatever the case, the fact is that many kids today start to show signs of the changes of adolescence during the tween years. And many of the tribulations that come from this shift can be directly attributed to what’s going on in their brains.
Tips for Physicians
- Keep up with the latest discoveries about the adolescent brain and its implications for the advice you give to tweens, teens, and parents.
- Encourage parents to learn about adolescent brain development. It gives them the needed perspective to weather the ups and downs that come with adolescence.
- Take a minute during exams to connect with teens about school and their interests. This will build trust and motivate tweens and teens to share questions or concerns.
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A baby is born with 100 billion neurons, each having about 10,000 dendrites. That means that there are about one quadrillion possible connections. However, only 17% of those neurons are connected or wired together at birth. Until recently, neuroscientists thought that the other 83% were “wired” by the age of 8. From then on, the thinking went, kids matured by simply using the circuits they had already established. Maturity came with experience.
The groundbreaking research of National Institute of Mental Health neuroscientist Jay Giedd, M.D., has turned that assumption upside down. His functional magnetic resonance imaging (fMRI) studies of normal adolescents clearly demonstrated that the adolescent brain is not the finished product we thought it was. He discovered major brain “circuits” still developing throughout the teen years. Now we know that the adolescent brain is very much a work in progress.
The latest scientific information about the teen brain has given us a whole new sense of what adolescence means. The new neuroscientific findings shed startling light on nearly every issue facing adolescents and the adults who care for them—from violence to sleep habits, sexuality to depression, impulsive behavior to defiance. Most important, the new research offers a crucial opportunity to help kids through a difficult stage of life. Understanding just what is going on in their heads helps us have compassion for what they are going through, but it also suggests particular tactics and strategies parents and physicians can use to serve them.
Suggested Readings
Anderson CA, Bushman BJ. Psychology. The effects of media violence on society. Science. 2002;295(5564):2377-9.
Bartels A, Zeki S. The neural basis of romantic love. Neuroreport. 2000;11(17):3829-34.
Damasio A. Descartes’ Error: Emotion, Reason, and the Human Brain. New York: Avon; 1994;3-17.
Diamond M, Hopson J. Magic Trees of the Mind: How to Nurture Your Child’s Intelligence, Creativity, and Healthy Emotions from Birth Through Adolescence. New York: Plume; 1999.
Eliot L. What’s Going on in There? How the Brain and Mind Develop in the First Five Years of Life. New York: Bantam; 1999.
Fisher H. Anatomy of Love: A Natural History of Mating, Marriage, and Why We Stray. New York: Ballantine; 1994.
Giedd JN, Blumenthal J, Jeffries N, et al. Brain development during childhood and adolescence: a longitudinal MRI study. Nat Neurosci. 1999;2(10):861-3.
Giedd JN, Vaituzis AC, Hamburger SD, et al. Quantitative MRI of the temporal lobe, amygdala, and hippocampus in normal human development: ages 4-18 years. J Comp Neurol. 1996;366(2):223-30.
Gilbert S. A Field Guide to Boys and Girls: Differences, Similarities: Cutting-Edge Information Every Parent Needs to Know. New York: Harper Collins; 2000.
LeDoux J. The Emotional Brain: The Mysterious Underpinnings of Emotional Life. New York: Simon & Schuster; 1996.
Rohde P, Lewinsohn PM, Kahler CW, Seeley JR, Brown RA. Natural course of alcohol use disorders from adolescents to young adulthood. J Am Acad Child Adolesc Psychiatry. 2001;40(1):83-90.
Schwartz IM. Sexual activity prior to coitus initiation: a comparison between males and females. Arch Sex Behav. 1999;28(1):63-9.
Schwartz RH. Marijuana: a decade and a half later, still a crude drug with underappreciated toxicity. Pediatrics. 2002;109(2):284-9.
Slotkin TA. Nicotine and the adolescent brain: insights from an animal model. Neurotoxicol Teratol. 2002;24(3):369-84.
Strauch B. The Primal Teen: What the New Discoveries about the Teenage Brain Tell Us about Our Kids. New York: Doubleday; 2003.
Thompson PM, Giedd JN, Woods RP, et al. Growth patterns in the developing brain detected by using continuum mechanical tensor maps. Nature. 2000;404(6774):190-3.
Wolfson AR, Carskadon MA. Sleep schedules and daytime functioning in adolescents. Child Dev. 1998;69(4):875-87.
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Who’s in Charge Now?
The key finding from the latest fMRI studies by Giedd and others concerns the part of the brain we know as the prefrontal cortex (PFC). The PFC acts as the executive center of the brain. This “CEO” of the brain is responsible for making decisions, weighing judgments, and considering consequences. We now know the PFC is not developed when kids reach adolescence. In fact, the wiring of the PFC doesn’t finish until the late teens or early 20s.
Think about it. The PFC is the part of the brain that allows us to effectively plan ahead, control our impulses, and filter what comes out of our mouths. And just when tweens are beginning the physical changes of puberty—a transformation that is nearly always awkward—the prefrontal cortex, the part of the brain responsible for emotional regulation is under construction. When you combine an immature prefrontal cortex with the emotional turmoil triggered by the increased production of growth hormones, we start to understand that the moodiness, quickness to anger, and risk-taking long associated with the teenage years is caused by what’s going on in their brains.
Truly a Work in Progress
The second most important revelation in the new neuroscientific research concerns the way the brain develops. The argument about genetics versus experience or nature versus nurture is quickly coming to an end. Neuroscientists such as Marian Diamond, Ph.D., at University of California, Berkeley, and Joseph LeDoux, Ph.D., at New York University, have shown that brain development is not an either/or proposition. The brain is shaped by both genetics and experience working in tandem. However, not all experiences are equal. Experiences that we have during the brain’s growth spurts are particularly important. That’s why, for example, it’s important to detect and treat ear infections in young children. An untreated infection could interfere with the wiring taking place in the auditory cortex.
Now that we understand that the brain’s growth continues throughout adolescence, it makes sense that teens’ experiences have a greater impact than we previously thought.
We’ve understood the importance of early childhood development for years. That’s why pediatricians are so dedicated to infant nutrition, and it’s why the market for early childhood educational products has boomed in recent years. The results are easy to see. Kids who grow up healthy are much more likely to turn out happy and healthy.
Even though it’s not as apparent, the impact of experience on adolescents is equally profound. The science behind this phenomenon is easily explained: The neurons that fire together wire together. In other words, when adolescents engage in any activity, they activate connections, and repetition reinforces them. The more often those neurons are activated, the more likely they will fuse together to form an established neural pathway and, therefore, the more likely the brain will remember how to engage in that activity. From doing homework to watching television, from shooting free throws to driving a car, the actions performed during adolescence will set the precedent for adult patterns and abilities.
A second body of research, much of it concerning the impact of media on children, confirms this finding. Behavioral patterns are shaped, for good and for bad, by what kids do with their time. When kids play a lot of violent video games, for instance, they are more likely to be aggressive in the real world. In fact, in one study I helped conduct, the kids who were most prone to aggression but did not play such games engaged in less bullying and fighting than the normally mild children who did play violent games. The new frontier in research on the impact of the media is brain-based, and these studies are confirming what the behavioral research has long shown. Recent fMRI studies at Indiana and Michigan State universities on students who play violent video games show the aggression centers of the teen brain activating while the prefrontal cortex deactivates.
What Can Physicians Do?
Physicians are not always on the frontlines with adolescents the way parents are, but as guardians of patient health they can have a profound influence. First, they can advise parents, who often look to physicians for guidance and help with distinguishing normal from abnormal behavior. Second, they can share the new brain research with adolescent patients and advise them to be extra careful. They can explain that their brains make them prone to risky behavior and that ill-advised exploits with alcohol, drugs, sex, and driving can have lifelong consequences.
There is one thing the latest brain research will probably never be able to prove, even though it’s indisputably true: Kids need and deserve demonstrations of love from the adults who care about them, including their doctors. They can also benefit from the information that physicians provide about the new insights science has provided about their brain development and how that influences the ways they think, feel, and behave. Every kid tries to grow up the best way he can. Every kid, no matter how difficult, deserves help getting on the right track. The investments we make now to understand the biology of the teen brain will pay off as we help them deal with the challenges of the teen years and move into adulthood. You don’t have to be a neurosurgeon to see that. MM
David Walsh, Ph.D., is president of the National Institute on Media and the Family and the author of Why Do They Act That Way? A Survival Guide to the Adolescent Brain for Your and Your Teen.