Growing Up: Neuroscientist Jensen explains new findings about adolescents’ minds

​​Frances Jensen describes ​herself as an accidental author. But her expert knowledge of the adolescent brain and its neurological development is no accident at all.

Jensen spoke on the morning lecture platform Wednesday in the Amphitheater with a speech titled “The Teenage Brain Explained.” Her expertise does not end with her academic research but extends to her two “living experiments” — her teenage sons.

She is the co-author of The Teenage Brain: A Neuroscientist’s Survival Guide to Raising Adolescents and Young Adults, which she described as neither a self-help nor psychology book.

“These are facts culled from the most recent research in the last five to 10 years,” she said. Her intention was to both inform and debunk myths about teenagers and their parent-bewildering brains by using cutting-edge statistics and data.

First, she confirmed what might be obvious for some: Teenage brains are fundamentally different than adults. The human brain is the last muscle to fully develop, she said, and does not finish until the mid-20s.

The process occurs from the back to the front. The last part of the brain young adults develop is the prefrontal lobe, the section responsible for personality, judgment and decision-making. It’s this part that “makes us human,” she said.

But not too long ago, adolescence as a concept and practice didn’t exist, Jensen noted.

“I think we all thought puberty was the end, but science shows that is not true,” she said. It has only been in the last few years that real progress has been made in the neurologic science of young, developing brains.

Teenagers have much higher synaptic plasticity than adults, making them much more malleable, more influenced by their experiences. Synapses are most numerous and responsive during the teenage years, Jensen said. This makes their brains more apt to learn quickly and efficiently.

“When we think or move, it’s a relay race of electrical signals traveling across the axons of our brains,” she said, referring to the connectors between neurons. “Right now, many of [the audience] are creating new axons as you are learning.”

Brains develop through the practice effect; the more people do certain activities, the stronger and quicker the synapses that govern that behavior become. This is especially true of adolescents.

“When we learn, we’re building synapses,” she said. “As adults, we prune them.”

According to Jensen, how people treat their brains when learning is more important than the subject or amount of learning. Even IQs can change during adolescence — a fact that shocked Jensen.

“This astounded me. For the longest time, I thought IQ was like a branding we all had, but it’s just not true,” she said.

On the flip side, what makes teenagers sponges for new information also makes them more susceptible to learning bad habits and addiction. Substance abuse in adolescents can actually lower IQs. By the same token, proper education can increase a teenager’s IQ considerably.

“They learn faster and get addicted faster,” she said.

Jensen said there is a disturbing similarity between learning and addiction. Teenagers are much more likely to become dependent if they regularly abuse substances like alcohol, cannabis or cocaine between the ages of 13 and 17.

Alcohol, for example, has more lasting effects in adolescents than adults. It can permanently alter synapses by stopping them cold and even lead to brain damage if binged.

They also suffer greater consequences from sleep deprivation, stress and excessive multitasking, she said. Adolescents neurologically have a different sleep cycle than adults and, contrary to the common myth, they are not lazier than adults.

“[Their brains] are why on weekends we see our kids waking up at 10 or 11 a.m.,” she said. “Waking them up at 6 a.m. for school is like waking an adult up at 3 a.m. and sending them to work. And yet when do we have our SATs? Seven or 7:30 a.m., pencils sharpened. We’re probably not getting the best out of them.”

Stress is also an inhibitor to young adult development. She likened the growing emphasis on testing to an actual stress experiment conducted on a rat. It was put in an unfamiliar cage while a cat prowled outside of it. In her metaphor, the rat was a student, the cage a classroom and the cat a teacher or parent.

For young adults who already have enhanced emotional responses, these environments can increase the incidence of depression in adulthood.

“They perceive the world in much higher contrast than adults do,” she said.

While she spoke mostly in non-specific gender terms, she mentioned girls are usually two to three years ahead of boys in development. Boys do catch up, she said, but the lag is indicative of the problems boys commonly have in school academically and socially.

In addition, new studies have shown distinct differences in the neural processes of young boys and girls. Boys’ brains primarily develop back-to-front while girls’ develop side-to-side. This creates an earlier, easier communication for girls across the right and left hemispheres.

She closed by discussing the legal ramifications of the research. In Jensen’s view, it is absurd that a mere minute after an adolescent’s 18th birthday they are legally an adult, when science proves it is not so black-and-white. She cited the wisdom of Supreme Court Justice Antonin Scalia, who wrote that “adolescence is akin to mental retardation.”

Jensen was amicus curiae on two Supreme Court cases — petitioners Graham and Sullivan and petitioners Miller and Jackson — of adolescents 17 years and younger who had committed capital crimes.

“I talked about how, at least on a case-by-case basis, [the judges] think about potential rehabilitation and parole at some point rather than mandatory life without parole. And they took it,” she said to applause.

Mental illness, such as schizophrenia, specifically shows up in late adolescence because it is located in the prefrontal lobe, which adolescents do not have full access to until late teens and early 20s.

“There’s a lot ways to use this data. It’s a paradoxical state with strengths and weaknesses,” she said, “But the emerging information has a lot of applicability to parents and teachers, and I hope it help them count to 10 and not alienate their young colleagues.”


Q: Dr. Jensen, could you comment on the effects of meditation and mindfulness practices on developing brains?

A: That is a wonderful topic. So, I couldn’t get to everything, but we think a lot about what we call our so-called digital invasion of our brains. And these kids are growing up with a very different experience from their parents, and sometimes even from their older siblings. It’s so rapidly emerging. There’s so much data coming at these kids. And I’d like to just say a couple things about the Internet and social networking and particular vulnerabilities. So number one: Remember what I said about addiction? Well, video game addiction and Internet addiction has been shown to be one and the same, using the same reward circuits, as other kinds of addiction. So it’s an addictive behavior just like drug addiction. So they are actually locking onto this and can become Internet-addicted to a greater extent than adults, so that’s kind of an issue. The other part of it is that the amount of stimulation that’s coming at these brains — look, teenage brains haven’t changed in millennia, its always been this biology, we’re just learning about it now. But the environment is changing, and we’re seeing so much more influx through the Internet and social networking, which can be very good for learning, but a lot of social stress can happen there, a lot of visual imagery that’s very stressful and that can leave marks on this scaffolding brain. And you think of cyberbullying, for instance, what can happen with that. I cite a story about a young man who was a Rutgers student and who actually was bullied by his roommate. A videocam was put on in his room, and he didn’t know it, and it went viral, and it was such a disturbing thing for this young man, that he jumped off the George Washington Bridge and killed himself. Because of what was a schoolyard prank of yesteryear — that could have just been a photograph on a bulletin board torn down with 10 people seeing it — the world saw it, and it went viral, this particular image, and he felt so compromised. So they’re playing with fire, and they don’t know it. They’re the same teenagers we’ve all been, making stupid mistakes without thinking because you’re not using your frontal lobe, but the Internet is sort of giving, unfortunately, kind of more power, unintentionally, they’re getting more power for these thoughtless acts that are clearly done without their full frontal lobe conductivity. So that’s part two. Part three: What about the digital, the rate in stimulation at our brains? Mindfulness: just like exercising, which we now don’t walk to work, we don’t walk to school, we don’t get exercise as part of our daily lives, many of us take time out of the gym, schedule a personal trainer, schedule some time, make effort. Unfortunately, it’s starting to look like we’re going to have to be doing that with downtime for our brains, and we don’t know the implications right now of what’s happening in early childhood. It’s actually started in early childhood. It’s been shown that the amount of screen time in early childhood does impair subsequent learning and can have some downstream effects on IQ. The American Academy of Pediatrics has just released a document about limiting screen time for children and there’s also adolescence now. The science is just emerging. That’ll be for the second edition of this book, but it is emerging. And it’s looking like we ought to be having some downtime and mindfulness. Interestingly, a lot of middle schools, I learned recently some of the Friends schools, are actually building in mindfulness training to middle schoolers so that you actually can take a moment to sort of compose your, what we call, default-mode networks. Actually, a functional MRI shows that if you’re just doing nothing, your brain is sort of just churning. We need that time because that reinforces our brain function, to have that time just to churn. Not asleep, but just awake, meditating.

Q: We have a huge number of questions regarding the effects on the brain of antidepressants, ADHD meds, Prozac and the like.

A: Well, I said about the implications for medical treatment for psychiatric disorders. I think many of you remember the situation about six or seven or eight years ago with Zoloft actually increasing suicidality in teenagers and adolescents. Well, that’s because their brains are not simply adult brains with fewer miles on them. They look like adults, but guess what, their brain is only 80 percent of the way there. And their receptors that I showed you, those synapses, are different. They’re configured differently. They’re more sensitive in some ways to the brain, and they also change as a result of the treatment. So a lot of research now that’s going on is like “how do we treat psychiatric illnesses and other psychiatric conditions and cognitive conditions in the adolescent brain compared to the adult?” I think about this a lot for epilepsy, which is actually prevalent in childhood and adolescence to a greater extent than adult. I’ve been quoted as saying no more hand-me-down drugs for the adolescent brain. A lot of our drugs get recycled without actually having true trials in children and adolescents. Recently, in the last five years, the FDA has changed that to give companies who make drugs extra time of patent life if they actually can prove they’ve looked at the drug in the young population and it’s not just simply a hand-me-down at some calculated lower dose that could have a really unusual effect like the Zoloft did. So I think drugs do change the brain, and you respond differently.

Q: How does sugar addiction affect the brain?

A: There’s no science on that at all. But we do know that too much sugar can cause, like, a rebound of very low sugar several hours later, because you have a burst of insulin, and that’s not good for the brain to be seeing these bigs up and downs. We like to homeostasis, which means keeping a balance, our brain is forever trying to do that. So spikes in sugar will sometimes be associated with drops in sugar, and your brain does not do well. There’s not enough energy actually going into the learning process, and that’s why people get drowsy and logy.

Q: Does exercise play a role in brain development?

A: Exercise plays a role in learning and memory, and so if you want to process that logically through, it should have a very good effect on building of synapses during brain development. It also allows our brains to go into different modes, like the default mode, when you’re running or jogging. It’s probably very good in this window of development.

Q: Is sexual addiction like drug and alcohol addiction? Is there a difference between genders?

A: There is evidence to show that porn addiction, for instance, is actually tapping into those same addiction circuits. Some studies have shown that young men may be accessing those kinds of sites more than women. And as I said, the interesting thing here is when you think about the frontal lobe being connected last, but the sexual desire area is back here. So it’s connected before the frontal lobe. So you are much more exuberant, under the influence of that part of your brain during adolescence, where you don’t have the reasoning and the, “Okay, okay, calm down,” kind of access to your frontal lobe.

Q: A lot of questions about school policy and the role of adults and parents in seeking to advocate for change. Should we petition our school boards to start high school at 10 a.m.?

A: Well, in an ideal world, that would be great. But it isn’t going to be practical for a number of reasons. Parents can’t, at least at this point in the history of our country, wait to go to work until 10, with transportation issues. But what we can do is think about when we give exams, some of the more rigorous, where we put exercise. Some schools are experimenting with putting exercise up front. There are other schools that are actually — and this is actually very interesting because this happens in medical school — I can speak to this as a parent of a medical school student and also a medical school professor, that medical schools are now having the kids — nobody comes to lecture anymore. They’re all videotaped. They’re streamed online and archived. So what do they do? They wake up at 10, 11, they find their fertile time for learning, and they sit with a cup of coffee on their bed and watch the lecture. But they come to school to have the group tutorials and seminars where they are essentially doing the homework. It’s like upside-down learning: The didactics are being done at home now, and the group think, the working through the problem solving, is happening at school in small groups. Which, I think, is actually very cool and I think is something I know high schools are experimenting with more. Sometimes these kids do better looking at the lecture or taking their math lecture at 10 o’clock at night when their parents are asleep than at 8 o’clock in the morning when they’ve been pushed into school.

Q: With respect to the medical school environment, my wife teaches at the Morehouse School of Medicine. She’s an advocate for replacing all stationary desks and chairs with stationary cycles so that the physicians are learning to be in motion. Please comment on the effect of concussions in sports on the brain.

A: I left that out, and I figured somebody was going to ask that. I actually have a couple of slides, but I can just describe it to you. So concussions are increasingly being recognized. They’ve been going on for a while. But I think our sports are becoming somewhat more impact. And don’t forget, we talk about concussion in schools, but let’s just remember, in the military, those are teen brains going to war. And they’re more vulnerable, too. So teenagers and young adults are more vulnerable to the effects of concussion. That’s absolutely been shown. That’s a fact. And the irony is that young soldiers are also in this window. So what happens is that when you have an impact, even if it’s not a puncture wound, it’s an impact. Your brain is like jell-o inside a hard, encased ceramic bowl. And if I have impact here it goes, “chu-chu,” like that, it’s called coup contrecoup, side opposite side. It goes back and forth, bruising, bruising, back and forth. And the inside of your brain has white matter. Remember, I told you that’s where all the connections are, the mantle of gray matter, but the stalk and the stem of the brain is white matter? It’s not as well developed in adolescents. So whereas adults have a little more rigidity and structure, it’s much more floppy in the adolescent brain, and they definitely have more injury. Interestingly, when you look at academic performance, adolescents actually have worse school academic performance after a concussion than even a child and a lot less than an adult. So it seems to be a very vulnerable window for a concussion and concussive injury. And the repetitive concussions are actually causing — if you have a repeat concussion, you actually take longer to recover. It usually takes two to three weeks for most people to recover from their first concussion. If they’ve just briefly lost consciousness, they can be irritable, problems with memory, sleep disturbances, attention problems. Those tend to stretch out to about six weeks with the second concussion, and it gets longer. Some of our professional sports players, as you know, have clear evidence of a drop in their learning ability. And those with severe concussion have developed chronic traumatic encephalopathy. This is the thing the football players have. And what happens is they are developing early Alzheimer-like changes in their brains as a result of this repeated trauma. Your brain does not like to be impacted a lot and repetitively. You start to develop sort of premature aging in your brain, and that’s what’s happening to these football players.