The ever-unpredictable teenage brain

Text by Tim Hyland

For years, the conventional wisdom within the field of neurology was that the adolescent brain was every bit as developed as the adult brain—and that, by extension, teenagers were every bit as equipped to deal with the stresses and dramas of their lives as their parents.

Teenage Brain

For years, the conventional wisdom within the field of neurology was that the adolescent brain was every bit as developed as the adult brain—and that, by extension, teenagers were every bit as equipped to deal with the stresses and dramas of their lives as their parents.

Frances Jensen is among the researchers who have, over the past several years, shown that conventional wisdom to be way, way off base.

Teenage Brain

But unlike some of her colleagues, Jensen’s certainty that the teenage brain is not nearly as developed as previously thought is not rooted in science alone. It’s also rooted in her personal experience raising her two sons.

“It was just so clear to me as a parent that something was going on with my children,” says Jensen, chair of the Department of Neurology in the Perelman School of Medicine. “I remember thinking, ‘What is going on?’ Their little cherubic faces were changing and they were acting differently and sometimes doing maddening things that were just inexplicable to me. But I decided to turn my frustration into curiosity. As a researcher, neurologist, and a parent, I knew I could explore this further, and I started finding amazing facts that really seemed to captivate people.”

The teen brain, and what she discovered as she reviewed the emerging—and very recent—body of research on the adolescent brain seemed to dominate conversations with her fellow high school parents at football games and other gatherings. These conversations would eventually evolve into a presentation, called “The Teen Brain 101,” that Jensen delivered with great success at high schools, science museums, and even professional conferences. National Public Radio took notice, as did the “TODAY Show,” and before long, Jensen landed an offer to turn her knowledge and experience into a book.

That book, “The Teenage Brain: A Neuroscientist’s Survival Guide to Raising Adolescents and Young Adults,” was published in January, and has since proven to be a major hit. The popularity of the book, says Jensen, has been a pleasant surprise.

“Until a decade ago, there had been very little research on the human brain,” she explains. “Neuroscientists had done a lot of work on the aging brain, and they did a lot of work, too, on the other end—with early brain development. But this middle part really wasn’t looked at.”

Once researchers began looking at the adolescent brain specifically, they discovered that most of their old ideas were wrong. Very wrong, in fact.

According to Jensen, neuroscientists now understand that teenage brains simply aren’t anywhere near as developed as once believed. Specifically, that lack of development is tied to the shortage of a fat called myelin within the frontal lobe of teenage brains. The frontal lobe is the section of the brain responsible for controlling decision making, and while the lobe itself may be fully developed in teens, myelin growth isn’t. That’s because myelin—which helps “insulate” the brain connections and speed delivery of brain signals—begins to develop at the back of the brain, then moves forward.

Given the slow pace of myelin growth, this means the brain may not be fully developed and fully functional until an individual reaches their 20s or even their early 30s.

Saddled with an immature prefrontal cortex and frontal cortex, teenagers have more difficulty with impulse control, with empathy, with risk-taking, and more. They are more prone to develop an addiction than adults, and to suffer from extreme stress, too. They are more likely to be moody, to be unpredictable, and to make poor choices—including decisions, for instance, about what is appropriate to post on social media.

“It can give you pause when you think about what our environment holds today,” says Jensen. “Teens who are naturally prone to risk-taking and poor judgment can get their hands on social media, and what would have been a minor schoolyard prank 25 or 30 years ago—a Polaroid of somebody in an inappropriate situation that maybe 10 people would see—can now go viral and then even go global. They are playing with fire. But they are prone to  clicking that button, because that’s impulse, and sometimes they can’t control it.”

In other words, Jensen says, the dangers are real. But it’s important to note that the same brain that exposes these teens to dangerous habits and behaviors also makes them more adept than adults at skills such as memorization and more capable of developing a high-level musical talent. Their brains are learning and growing every day, and both the bad and the good input can and will make a lasting impact. What’s important, she says, is for parents to do what they can to help their teens achieve some kind of balance.

Having survived her children’s teenage years, Jensen says she is hopeful that her book can offer comfort, and convey useful knowledge to parents.

If nothing else, she says, the book may make clear to parents that there’s nothing necessarily “wrong” with their teen, and that their unpredictable behavior is simply part of growing up.

“Why did this book get so big? It’s because everyone has been a teenager, and every parent has had or will have a teenager,” Jensen says. “It’s a universal thing. This was just a niche that hadn’t been written about before in this way.”

[updated on June 9]

Originally published on .