The Incredible Cognitive Potential & Vulnerability of the Teenage Brain
Research in the past 10- 15 years has shown that our brains continue to develop in fundamental ways through the teen years and even into the late 20s and 30s. In fact, Jensen argues in her new book, The Teenage Brain: A Neuroscientist Survival Guide to Raising Adolescents and Young Adults, the teenage years comprise one of the brain’s most critical periods for development – likely every bit as crucial as early childhood. “That seven years in their life is, in a way, as important as their first seven years of life,“ Jensen says. “It is probably one of the most important seven-year periods in their entire life. “
Emerging brain development science is changing the way we view team behavior: why teens can seem so moody and disorganized, why they sometimes make such short sighted decisions and why many serious mental illnesses begin to emerge in adolescence.
New discoveries are also revealing that teen brains are far more vulnerable than we thought, revelations that are destined to give rise to a new war over how parents, teachers and society should treat teenagers – with more freedom or more rules?
Recent scientific thinking on brain development is a fundamental shift, one that is poised to make adolescence, rather than childhood, the latest battleground in the fight to make a generation of smart, healthy and independent adults.
This past year has seen the release of psychiatrist Daniel Siegel’s best-selling book Brainstorm: The Power and Purpose of the Teenage Brain, along with Age of Opportunity: Lessons from the New Science of Adolescents by Temple University Psychology professor Lawrence Steinberg and the updated re-release of psychologist David Walsh’s influential 2004 book on teen brains, Why Do They Act That Way? A Survival Guide to the Adolescent Brain for You and Your Teen.
Among the most popular misconceptions about brain development is the idea that the most important changes happen in the first three years of life. This idea has been the source of much parental anxiety over the fear that they provide enough stimulation to their infants before their synapses are lost. Paul Howard Jones, a professor of adolescence and education at the University of Bristol believes that parents can breathe a sigh of relief and pack up baby Einstein’s toys.
An improved understanding of the developing brain carries a growing acknowledgement that teenagers are uniquely susceptible to great risks. Behind the seemingly invincible teenage boy with the booming voice and adult body is a brain that is incredibly vulnerable to everything from sports related concussions to mental illness and addiction. New research is uncovering ways in which the activities that so often typify teenage years, such as experimenting with cigarettes, marijuana and alcohol, can lower teen’s IQ or increase susceptibility to mental illness later on. Chronic stress stemming from family violence, poverty or bullying has also been linked to changes in the teen brain that can raise the risk of mood disorders or learning disabilities.
Science is only beginning to understand just how crucial the teen years are to the person we ultimately become. “This is an incredible reveal of how much capacity we have that we never really realized we had at this age,” Jensen says, “but also that it has a price.”
At the heart of our understanding of brain development are two basic concepts gray matter and white matter. Gray matter consists of neurons, the brain cells that form the building blocks of the brain. White matter, are the connections that form between gray matter, helping to move information from one area of the brain to the next.
While gray matter growth is indeed almost completely finished by the age of six, white matter – the wiring between brain cells – continues to develop well into the 20s. In fact, says Jensen, “that wiring is only about 80% complete by the age of 18”.
The last area of the brain to be hooked up with white matter is the pre-frontal cortex, which controls insight, judgment, self-awareness and empathy – the brain’s so called executive functions.
Along with new wiring the brain of teen’s and young adults are also undergoing a process called myelination, in which those white matter connections are being coded in a protective fatty material. Myelin acts as a form of insulation, allowing signals to move faster between brain cells, helping to speed the flow of information in the brain. Since both the wiring to the prefrontal cortex, and the insulation, is incomplete, teens often take longer to access the prefrontal cortex is, meaning they have a harder time making judgments and controlling their impulses. The process of myelination continues into the 30s, giving rise to questions about how old someone must be to considered to have a fully developed ‘adult’ brain.
At the same time the teens’ brains are laying down connections and insulation, puberty has triggered pituitary glands to release hormones are acting on the limbic system, the brain’s emotional center. The combination of heightened emotions and an underdeveloped pre-frontal cortex explains why teens are often prone to emotional outbursts, says Jensen, and also why they seek out more emotionally charged situations, from sad movies to dangerous driving.
Hormones also appear to have a different effect in teens then they do in adults. The hormone THP, which is released by the body in response to stress, has a calming effect in adults, but actually seems to have the opposite effect in teens, increasing stress. It’s one reason why teens are prone to anxiety and post-traumatic stress disorder. It’s also a good reason, Jensen says, why parents and schools should be sensitive to the problem of bullying.
Along with new wiring, insulation and hormones, teens brains are highly sensitive to the release of dopamine, which plays on the areas of the brain that govern pleasure And helps explain why teens seem to take so many risks.
It’s not that they don’t know any better. In fact, reasoning abilities are largely developed by the age of 15 and studies have shown that teens are as accurate as adults when it comes to understanding if an activity is dangerous. Their brains are just more motivated by the rewards of taking a risk than deterred by its dangers. So even if they know something might be bad – speeding, drinking too much, and trying new drugs – they get more pleasure from taking the risks anyway.
Central to our understanding of how teens learn is ‘pruning’ – a period when the brain begins to shed some of the gray matter cells built up in childhood to make room for the growth of white matter. A long period of gray matter growth in childhood, followed by vigorous pruning in adolescence has been linked to higher intelligence, Jensen says.
It’s for this reason the Jay Giedd, an expert in child and adolescent brain imaging at the US National Institute of Mental Health, describes the teen years as a special period of ‘use it or lose it’ for the brain. Brain cells grown in childhood that continue to get used in adolescence form new connections, well those that go unused wither away. It’s also another reason why parents should be anxious about what happens during the teen years – adolescents now appears to be a period that can make or break a child’s intelligence.
A significant consequence of pruning is that IQ, once thought to be fixed for life after childhood, can in fact change dramatically during the teen years.
British researchers at University College London tested the IQs of 33 teams age 12 to 16 and then retest them four years later. They found some teens IQ rose as much as 18 points, the difference between being average and being gifted. They attributed the changes to increases in grey matter in two areas of the brain that govern speech and language, as well as hand movements. In a follow-up study, the same researchers found that changes to verbal IQ were strongly linked to reading abilities in early adolescence, suggesting that changes were not simply genetic. They recommended that children with dyslexia be given audiobooks of their verbal IQs don’t deteriorate with age.
A study published last year of Swedish teenagers linked a drop in IQ between ages 13 and 18 with a higher risk of developing a psychotic disorder, such as schizophrenia as an adult.
Just as teens’ brain development appears to make them highly sensitive to learning new skills, science is beginning to reveal just how vulnerable teens are to learning the wrong things.
Learning is a process of repeatedly exposing the brain to something that stimulates the production of dopamine, which strengthens connections in the brain’s reward center and helps form new memories. Addiction, therefore, is simply a form of ‘overlearning’ by the brain, Jensen says. That process can be controlled by the prefrontal cortex, but since teens are so primed for learning and have less of an ability to access the prefrontal cortex, they’re also more susceptible to addictions.
What’s more, substance abuse can interfere with brain development in ways that can make teens more vulnerable to mental illness or even lower their IQ. Researchers have shown that students with higher levels of cotinine, a byproduct of nicotine, in their bodies perform worse on cognitive tests. Smoking also seems to be related to less active prefrontal cortexes in teens and appears to damage parts of the brain that produce serotonin, and lower levels of serotonin are linked to depression.
Other studies have linked smoking in teams to alcohol abuse, which itself has a devastating effect on both memory and intelligence. And it turns out smoking pot may be far worse for the team brain than previously thought. Recent studies have linked regular marijuana use and adolescents to smaller brain volume and more damage to white matter. Smoking daily before the age of 17 has been shown to reduce verbal IQ and increase the risk of depression. This can be a particular problem for teens with ADHD, who researchers have found are far more likely to abuse both cigarettes and marijuana than other teenagers.
For teens who get a thrill from binge drinking and getting high, the consequences may be dire – and possibly, permanent.
Alcohol, for instance, can affect the developing brain teen brain in myriad negative ways: causing potentially permanent damage to the hippocampus, which helps the brain form long-term memories, a critical aspect of learning. American researchers have also found that teens who start drinking before the age of 15 were four times more likely to become alcoholics later in life than those who held off until age 21.
That research comes with a warning for parents who think that as long as their teenagers drink at home under supervision, they’ll be safe from the temptation to abuse alcohol. Studies have found that the more teens a drink at home, the more they will drink elsewhere and the higher their chances are of becoming an alcoholic.
It’s not just drugs and alcohol that can cause long lasting damage to the teen brain. Chronic stress is also proving to permanently alter brain development, increasing the size of the amygdala, which governs the emotions, and reducing the size of the hippocampus. The end result may be a brain that is hardwired for anxiety, depression and learning disabilities.
As well, studies a video game addicts have shown their brains develop differently: excessive gaming appears to enlarge areas responsible for memory and visual spatial skills, but shrink areas of the brain responsible for speech, memory, emotions, and areas responsible for inhibiting impulsive behavior.
In an era marked by an ideological tug-of-war over how best to raise our teenagers, what’s a parent to do with this new science of the teenage brain? More rules? Or in intervening too much, do parents risk raising teens whose brains never learn how to become an adult?
In the Teenage Brain, Jensen puts herself squarely in the camp of the highly involved parent. She encourages parents to proof read their teen’s homework, help them make lists to prioritize their assignments, watch them as they do school work to see if they’re getting distracted and to not be afraid of ‘sounding like a broken record’ by reminding teens over and over again about the dangers that could befall them.
She encourages parents to ‘be your teens frontal lobe’s’ and to ‘try to think for your teenage sons and daughters until their own brains are ready to take over the job’. Jensen argues that it is a parents’ job to protect their teens from their own often short-sighted behavior, while allowing them enough room for ”safe failures”.
“Your kid doesn’t see the fact that if they fail all of their classes in the 11th grade they won’t be going to the kind of colleges they want to go to, or go to college at all”, she says. “That’s why you’re a parent. That’s why they ‘re not off living by themselves. There is a point at which I think you have a moral responsibility to intervene”.
In the quagmire of parental advice, it’s no surprise that the counter argument to the neuroscience approach to parenting is robust, and passionate. Psychologist Robert Epstein, author of the Case Against Adolescents: Rediscovering the Adult in Every Teen, believes that adolescent rebellion has little to do with brain development and lots to do with how society treats teenagers. He argues scientists have it backward: teens don’t act out because they have immature brains struggling to navigate an adult world, but because they have adult brains railing against a society that treats them like children.
“Put yourself in their shoes”, says Epstein. “Why they’re stealing your stuff and why their room is a mess is because they have very limited ways in which they can demonstrate their power and their independence and some of them will demonstrate it in destructive in self-destructive ways”.
Epstein has six children, including two teens and two adult children. He began changing his views on teen behavior when he caught his second oldest son, Justin, then 14, stealing his truck. Epstein hauled him down to the police station to scare him straight. “But inside my head I realize: wait a minute, he’s never gotten into an accident, he’s never got a ticket, obviously he knows how to drive”, he says. Why isn’t he allowed to drive? He now parents his middle children differently than he did his eldest, leaving most of the decisions, from whether they’re allowed to have dessert, to what courses they should take in school, entirely up to them. I tell them “you decide”, two words he says have completely transformed his relationship with his teenagers. His 16-year-old son now comes home from school and immediately starts doing chores without being asked.
Jensen agrees that the age limits society has placed on adolescents regarding the ability to drive, join the military, vote or drink alcohol have little to do with brain development science and are entirely random. She believes that we have to understand what teens are developmentally capable of, and gradually introduce things in steps.
Other research is challenging the notion that teens have a less mature and less connected prefrontal cortex and are therefore inherently more impulsive than adults.
At Temple University, Steinberg has used a car racing video game to show that when teens are alone they perform as well as adults on tasks involving a trade off of risk and reward. But when other teens are in the room watching, adolescents tend to make far riskier decisions. Adults show no difference if other adults watch them, suggesting that teen risk taking is likely social.
B.J Casey, Cornell University, found that teens could be less impulsive if they were offered rewards. The greater the reward, the longer teens took to make a decision, suggesting that parents trying to control a hot headed teen might want to offer rewards for good decisions rather than punishing bad ones.
According to Jensen and others, we could get so much more out of our teenagers – and who they become later in life, in many cases – If we took a different approach to this critical window of time.
Tamsin McMahon (Jan. 12, 2015)