November 12, 2002
Adolescence Is Tough On The Brain

First off, kids enterting puberty experience a big drop in their ability to read the emotions of others. So suddenly the likelihood for misunderstandings shoots way up:

Robert McGivern and his team of neuroscientists at San Diego State University found that as children enter puberty, their ability to quickly recognise other people's emotions nosedives. What's more, this ability does not return to normal until they are around 18 years old. McGivern reckons this goes some way towards explaining why teenagers tend to find life so unfair, because they cannot read social situations as efficiently as others.

Previous studies have shown that puberty is marked by sudden increases in the connectivity of nerves in parts of the brain. In particular, there is a lot of nerve activity in the prefrontal cortex. "This plays an important role in the assessment of social relationships, as well as planning and control of our social behaviour," says McGivern.

He and his team devised a study specifically to see whether the prefrontal cortex's ability to function altered with age. Nearly 300 people aged between 10 and 22 were shown images containing faces or words, or a combination of the two. The researchers asked them to describe the emotion expressed, such as angry, happy, sad or neutral.

The team found the speed at which people could identify emotions dropped by up to 20 per cent at the age of 11. Reaction time gradually improved for each subsequent year, but only returned to normal at 18 (Brain and Cognition, vol 50, p 173).

During adolescence, social interactions become the dominant influence on our behaviour, says McGivern. But at just the time teenagers are being exposed to a greater variety of social situations, their brains are going through a temporary "remodelling", he says. As a result, they can find emotional situations more confusing, leading to the petulant, huffy behaviour adolescents are notorious for.

This study may not have used subjects with an early enough starting age to detect the initial decline in ability detected in the previous study:

Another series of MRI studies is shedding light on how teens may process emotions differently than adults. Using functional MRI (fMRI), a team led by Dr. Deborah Yurgelun-Todd at Harvard's McLean Hospital scanned subjects' brain activity while they identified emotions on pictures of faces displayed on a computer screen.5 Young teens, who characteristically perform poorly on the task, activated the amygdala, a brain center that mediates fear and other "gut" reactions, more than the frontal lobe. As teens grow older, their brain activity during this task tends to shift to the frontal lobe, leading to more reasoned perceptions and improved performance. Similarly, the researchers saw a shift in activation from the temporal lobe to the frontal lobe during a language skills task, as teens got older. These functional changes paralleled structural changes in temporal lobe white matter.

During a time period when teens are already having a hard enough time sorting thru their own emotions they become far more sensitive to emotion-altering recreational drugs:

Researchers at Jefferson Medical College have evidence in animals that the young, adolescent brain may be more sensitive to addictive drugs such as cocaine and amphetamines than either the adult or newborn. The work may help someday lead to a better understanding of how the adolescent human brain adapts to such drugs, and provide clues into changes in the brain that occur during drug addiction.

Scientists led by Michelle Ehrlich, M.D., professor of neurology at Jefferson Medical College of Thomas Jefferson University in Philadelphia and a member of the Farber Institute for Neurosciences at Jefferson, and Ellen Unterwald, Ph.D., associate professor of pharmacology at the Temple University School of Medicine in Philadelphia, found a greater increase in a certain protein in the part of the adolescent mouse brain called the striatum following chronic exposure to drugs such as amphetamine or cocaine than they did in either very young mice or adults.

Such psychostimulant drugs affect the brain's striatum in different ways, potentially affecting both movement and locomotion, or the "reward" system. This "molecular adaptation," says Dr. Ehrlich, could be significant. "An increase in this protein may be important because it could also affect other molecules that could lead to long-lasting changes in the brain in response to psychostimulant drugs." The protein, called Delta FosB, is a transcription factor and plays a role in regulating gene expression. Earlier research by other scientists had shown increased amounts of Delta FosB in adult brains following chronic exposure to psychostimulants.

The team, which includes scientists at the Nathan Kline Institute in Orangeburg, New York, reports its findings November 1 in the Journal of Neuroscience.

Teens are at risk of developing life long harmful habits and their brains change in a way to puts them at greater risk of developing addiction to the demon weed:

When they did, researchers at Duke University found that adolescent brains respond more intensely to nicotine. The scientists injected rats with nicotine every day for more than two weeks, a dose comparable to what a typical smoker receives. In all of the rats the number of chemical receptors dedicated to nicotine increased -- a sign of addiction. But in adolescents, the number of nicotine receptors increased twice as much compared to adults.

"What we found is that the adolescent brain gets a lot more bang for the buck," says Theodore Slotkin, one of the scientists who performed the research.

A follow-up study published in the October issue of Brain Research showed that adolescent nicotine exposure caused permanent behavioral problems as well, especially for females. Even after two weeks with no nicotine, female rats were less interested in moving around and raising their young than counterparts who had never been exposed.

That may be because nicotine retards cell division in the hippocampus, a brain region that continues growing into adulthood in females, but not males.

The larger society is forcing teenagers to wake up earlier than their teen biological clocks are telling them to:

When teenagers insist that they are not tired at 9 or 10 p.m., they are very likely telling the truth. For reasons that are not fully understood, Dr. Carskadon said, their body clocks shift, so that their natural tendency is to stay up later at night and wake up later in the morning than when they were younger. But that inner clock often clashes with the outer world: early starting times in high school and demanding schedules of sports, clubs, music lessons, homework and part-time jobs.

There are consequences. For one thing, lack of sleep can interfere with learning: tired students have a hard time paying attention, and even if they do somehow manage to focus, they may forget what they were taught because memory formation takes place partly during sleep.

In "Adolescent Sleep Patterns," a book published in August and edited by Dr. Carskadon, she wrote, "The students may be in school, but their brains are at home on their pillows."

What's worse, the types of brain activities engaged in during adolescence probably have a significant impact on what cognitive abilities people will have the rest of their lives:

Even though it may seem that having a lot of synapses is a particularly good thing, the brain actually consolidates learning by pruning away synapses and wrapping white matter (myelin) around other connections to stabilize and strengthen them. The period of pruning, in which the brain actually loses gray matter, is as important for brain development as is the period of growth. For instance, even though the brain of a teenager between 13 and 18 is maturing, they are losing 1 percent of their gray matter every year.

Giedd hypothesizes that the growth in gray matter followed by the pruning of connections is a particularly important stage of brain development in which what teens do or do not do can affect them for the rest of their lives. He calls this the "use it or lose it principle," and tells FRONTLINE, "If a teen is doing music or sports or academics, those are the cells and connections that will be hardwired. If they're lying on the couch or playing video games or MTV, those are the cells and connections that are going to survive."

On the bright side, the spurts in cell growth in various parts of the brain during adolescence open up the possibility of therapies to boost intelligence by developing hormonal and/or gene therapies that would make the burst of nerve growth more intense. Also, with better understanding it may become possible to structure the institutions that deal with adolescents to better accommodate the developmental stages of their brains. Obviously, just moving starting times forward for schools is a fairly easy accommodation.

Update: These results provide a sense of just how much the mind changes during adolescence:

Researchers at studied the post-mortem cerebral cortexes of six 12- to 17-year-olds and five 17- to 24-year-olds. All of the individuals had been of normal health and intelligence. They studied 43 different areas in each brain hemisphere, measuring for cortical thickness, neuronal density and pyramidal neuronal size. Corrections were made for gender differences in the size of the brain.

The average pyramidal soma size was 15.5 percent smaller in the older age group than in the younger one. This suggests that these nerve cells undergo “pruning” or “streamlining” of their processing during adolescence, said de Courten-Myers.

Other measures of the brain were slightly larger in the older age group, including cortical thickness (1.9 percent), neural density (1.8 percent), the number of neurons/standard cortical columns (3.8 percent), neuropil volume/standard cortical column (3.1 percent), and neuropil volume/neuron (1.3 percent).

Update II The part of the brain that inhibits risky behavior does not fully develop until age 25.

A National Institutes of Health study suggests that the region of the brain that inhibits risky behavior is not fully formed until age 25, a finding with implications for a host of policies, including the nation's driving laws.

"We'd thought the highest levels of physical and brain maturity were reached by age 18, maybe earlier -- so this threw us," said Jay Giedd, a pediatric psychiatrist leading the study, which released its first results in April. That makes adolescence "a dangerous time, when it should be the best."

So that is why teenagers are so reckless. Hardly comforting news. You can know this and they will still be reckless after all.

Share |      Randall Parker, 2002 November 12 12:20 PM  Brain Development

Karin Klinger said at May 20, 2003 6:44 PM:

I find your information to be very accurate as to my sons symptoms at the age of 11. Thank you very much for this information as it gets very confusing for me sometimes what to make of his behavior.

Karin Klinger said at May 20, 2003 6:45 PM:

I find your information to be very accurate as to my sons symptoms at the age of 11. Thank you very much for this information as it gets very confusing for me sometimes what to make of his behavior.

ashley said at April 6, 2004 2:50 PM:

This was really great! This is just the type of message i needed from you. Since my daughter is 12 now, mabe she would understand this. You did a great job! I think I have time to reread it again!

Diane Steen said at April 26, 2005 11:52 AM:

Our Communities That Care group at Ballard High School in Seattle has been pursuing a program for parents on understanding - and parenting - adolescents. Your site has been useful in providing background information and we thank you. The more parents can read about the neurological development of teen brains the more likely it is that they'll be patient and understanding with their kids.

maggie said at June 3, 2005 9:15 PM:

Thanks, im currently 15 and Having A COmmunication wall being built betwen me and my mum. ill read this to her...

hey said at July 25, 2005 7:32 PM:

Are later-maturing girls MUCH better off than earlier-maturing ones?
I noticed that girl athletes in my school grew much later (assuming they don't eat much fats) than sedentary overweight girls (like me) in high school. I also read from some recent Adolescence book that research says late blooming girls are more socially adjusted? than earlier-maturing ones.
I come from an obese family. I admit I had a hard time due to my early puberty. I couldn't concentrate on my studies.
I wish I had known this sooner. Thank you very much for the info!

Mel said at August 2, 2005 12:46 AM:

I would just like to know which part of the brain grows THE MOST during puberty. Is it the frontal lobe, because I read an article that suggested it did, but this article is saying it actually doesn't develop much at all during puberty, which is what causes the risky behaviour. Am I just getting confused?

Doralicia Rascon said at September 24, 2005 9:25 PM:

I am mother of two teenagers and teacher of adolescentes. I found your information very refreshing and so much interesting.

Doralicia Rascon said at September 24, 2005 9:25 PM:

I am mother of two teenagers and teacher of adolescentes. I found your information very refreshing and so much interesting.

19 year old speaks up said at December 11, 2005 3:06 AM:

Update II The part of the brain that inhibits risky behavior does not fully develop until age 25. - This article is rediculous. It is cleary some biased excuse of an article to bash teenage drivers. Your data is stacked. All this article talks about is how all the "National Health Institute" approves of some very poor research done by Temple University in Pensylvania with UCLA Neuroimaging to back it up. This article spends more time talking about how teenagers are more likly to be involved in crashes than it does about actually telling us the research findings of the data. I wonder why that is? I think it is because the data discussed in this article is rubbish. First of all the group of people they used was only 2,000 people, and their ages range from 3 to 24.... How many of these tested people were teenage drivers? 2,000 people for a "law-making" study is very very low. I do not know the exact figure of how many people in America are in their late teens but I imagine it's got to be in the high millions... 60 million possibly? So you're going to take some research findings on 2,000 people and compare this to 60 million teenagers? That's 1 teenager in their study for every 30,000 actual teenagers, keeping in mind that is just a rough estimate. Even so, that is a scarce ratio to just start pinning laws down on teenagers and to make the assumption that we "take more risks" because of our neuroanatomy. Furthermore, you have to ask yourself how the teenagers in the study were raised. Don't you think their well developed personalities or digsruntled behavior could add to how risky they drive? Suppose the only teenagers in this study were poorly raised. I think that would make a big difference in how their "risky behavior" neuroanatomy works versus how a well mannered responsible group of teenagers neuroanatomy works.

Comments like this : "The results help show why teenagers are more likely to drink, take drugs or commit crimes in groups, he said. They're also reflected in auto crash statistics." are faulty. This data does not really show us much of anything because these people are just telling you what you want to hear about your teenage drivers.

I've been in three car accidents since I've been driving. In all three accidents I was following normal driving procedures and was doing everything correctly. I have not been at fault for a single one. In all three accidents I have been in the drivers were middle-aged women.

So does my experiances with driving show that middle-aged women don't know how to drive well? I don't think so, but hey I guess my argument is just as valid as yours.

Randall Parker said at December 11, 2005 9:56 AM:

Ignorant 19 year old,

The part of the brain that inhibits behavior really does not fully develop untill age 25. Teens really do get into car accidents at much higher rates than middle aged people.

You don't like the truth and so you childishly deny it. Well, the truth continues to exist even if you childishly deny it.

wanda said at December 11, 2005 9:42 PM:


Vince said at July 7, 2006 1:03 AM:

It's true. I find myself wanting to take all kinds of risks, that might get me killed, and I'm 22! Like ride a motorcycle. I can't think of a more dangerous thing to do, but I ride it every day to work, thirty or more minutes. One of these days I'm gonna get killed, and I'll have my brain to thank.

David Hurt said at August 29, 2006 11:18 AM:

Firstly I would like to mention that I have a 'Moderate Memory Learning Difficulty' or 'MMLD' for short. Despite this I have a wide range of interests, one of which is Human Evolution and another is the Human Brain and Mind and I am an Assistant Community Tutor at my local School of which I used to attend...I Totally Agree that the Brain doesn't Stop Developing until 25... And the risk side of it makes complete sense too, especially young Adults 18 to 24. For instance if anyone over 25 didn't do Drugs, there would still be people under 25 who would still come up with these ideas. Yet if anyone over 18 didn't do Drugs no one under 18 would do Drugs and it would be the 18-24s who would be the ones who would come up with the ideas of making Drugs. Where would the 16-17 year-olds come up with these ideas? They wouldn't....They are more impressionable than the 18-24s as they are still developing into Adults as they are still Adolescent Kids... Therefore the age of consent should be 18 for leaving home, joining the army, leaving school, driving and sex - (if the Government can't be bothered to make amendments so that the 14-17 year-olds aren't discriminated for having sex with each other, but the 20-40 somethings and 50+ year-olds 'are' discriminated against. And 18-19 are discriminated if they have sex with the 15- and anyone over 14 are discriminated against if they have sex with the 13-) etc etc... As even though the 18-24s Brains are still developing they are still Adults... Some People say with the situation with the Terrorists the 18-24s are also vulnerable in a way they probably are... But again if no one over 25 were Terrorists or believed in Terrorism, there still be people under 25 coming up with these ideas and it wouldn't be the 16-17 year-olds as like I said with the Drugs if no one over 18 did these things no one under 18 would do them, but the 18-24s especially the 20-24s would be the ones who would come up with these ideas... At 18-24 their Social Culture is more complex than with the 14-17 year-olds and the 13- year-olds...They are constantly coming up with new ways to communicate and exchange their ideas in Music and Fashion etc and the 18-24 year-old Brain is also more adapted to a higher Academic form of Learning too and if they are that clever then Obviously they are capable of coming up with more extreme and dangerous ideas than anything a 14-17 year-old would think of...This is not too say that all 18-24s are Bad people, but the ones who are more mischievous are most likely to do Bad things...And with the 14-17 year-olds again Not all of them are Bad, but the more mischievous 14-17 year-olds are more likely to follow the leader, thinking it is Cool or the leader is Cool or a Hero of some kind and they also tend to copy what they see on TV as well as with Peers and the irresponsible Adults among Society...

David Hurt said at September 6, 2006 2:31 PM:

In brief, what I'm trying to say above is - It really does Help explain why adolescent kids and the 18-24s take the risks that they do and Help people to understand the need for the 16-17 year-olds as well as the kids under 15 to be protected by law as they are still kids themselves at 16-17...And more impressionable than the 18-24s...As they are still growing into Adults...

It also explains why Mature-Young-Adults - (25-49 year-olds) behave the way that they do - which is a little bit wacky compared to people 50+… And it explains even why the Middle Aged - (50-69) and Junior Pensioners' or JPs for short - (70-89) behave in a young manner too as the Middle aged are only starting out as Senior Citizens and the JPs are like the second Middle Aged of Senior Citizen Life as they are still young compared to the - (90 somethings - (Young OAPs) and the 100+ year-olds - (Senior OAPs))...

Anita R said at March 8, 2007 11:26 AM:

Hi. I'm reading this and contemplating how to interpret this stuff. I tend to be a positive thinker, so here goes:
Perhaps teenagers have this hormonal/brain change in order to develop into free thinking adults. Thank goodness they are willing to take some moving away from their parents, getting out on their own, moving on with their lives, daring to have some intimacy with a boyfriend/ they are supposed to. Without a little gusto to explore the world they may not be brave enough to become independent adults. And by the way...we all went thru the same thing, so let's not say "they"...I remeber the feelings of bravery and the rush of "lets do something exciting"!
I ended up moving to another country. I understand it might be called "risky behavior"....and some teens get into recklessness in this state. But it is also this "excitement felt" that propells teens forward in life in positive ways. The difference is in the choises they make, in how they use this feeling of excitement. Are they choosing to be "dangerously reckless", or "beautifully brave" as they are stepping into the next phase of life. Our society seem to favor the recklessness in terms of what they put together for teens on TV and movies etc. It is up to all of us to help teach our young to be brave and beautiful, and how to make WISE choises. Let's help teens and ourselves learn to be brave enough to "Not go with the crowd" at times, and encourage them to use their own brain and understanding in making understand that WE are making our own reality all the time by the way we think and by the way we choose. That goes for adults and teens as well.....we have to begin with ourselves. By the way, it is the adults that make the movies and teach at home and in schools. Let's be brave and act beautifully.
I have a 17 yr old daughter and marvel at her bravery and beauty:) Footnote: we were both late bloomers, whatever that means. Physically that mind/spirit is a different story for us.
Love and Light to All who read

ian said at April 27, 2007 8:12 PM:

hi so i have still got a teenage brain antill i am 25 so i still got hormons going around lol

David Hurt said at July 3, 2009 2:55 AM:

At 18 to 24 your (a Twink or -female version Twinket) an Adult not an Adolecent. Your brain is developing to adjust to being in the world of Adulthood. To learn the skills you need in your adult life. At 10 to 17 adolecent brains are still developing into adults and their brains are jumbled, around 18 and half they become unjumbled and start to think in a similar way to older young adults -(25-40's) and seinor adults - (50+) although still naive, this is because they are only starting out as adults, especially the 18/19 year-olds.

Gwuff said at August 28, 2009 2:10 PM:

If the 18-24 year old brain is still developing, how can it be an adult brain? Doesn't an adult brain suggest that it has reached full maturity?

David Hurt said at January 3, 2010 8:15 AM:

Did you read August 29 and September 26, 2006 and July 3, 2009. 18 to 24 year-olds 'are' Adults, but their brains are still developing to cope with the adult world and learn the skills they need in the adult-world. Whereas Adolescent brains are still developing into Adults - (still jumbled until about 18 and a half).

18 to 24 year-olds don't have Adolescent brains or hormones. It's just their brains that are still developing, for the reasons I've mentioned.

Gwuff said at February 21, 2010 9:51 AM:

Surely, they're brains are not physically developing after 18 then. They're just gaining experience as a person. Also why 18 and a half, rather than just 18? Where does the precise figure come from?

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