Play Live Radio
Next Up:
Available On Air Stations
Watch Live

KPBS Midday Edition

The Scientific Reasons Why Teens Can Be So Moody

Dr. Frances Jensen, chair of the neurology department at the University of Pennsylvania Perelman School of Medicine, in an undated photo.
University of Pennsylvania
Dr. Frances Jensen, chair of the neurology department at the University of Pennsylvania Perelman School of Medicine, in an undated photo.

The Scientific Reasons Why Teens Can Be So Moody
The Scientific Reasons Why Teens Can Be So Moody GUEST: Dr. Frances Jensen, chair of neurology, University of Pennsylvania Perelman School of Medicine

Teenagers are known to be impulsive and moody and hard to wake up in the morning. The newest research finds they're not just doing things to annoy you. Scientists discovered that the human brain is not developed until late 20s. After Dr. Frances Jensen has written in this in her book , The Teenage Brain . She's in San Diego this week for the Society of neurosciences annual conference and also the chair of the neurology department of the University of Pennsylvania school of medicine. Michael Lipkin spoke with her. Your research shows that some of the traits that we associate with teens that has to do with the order that the parts of the blame test brain develop? The brain has lots of different regions and there's a region that is for rewards seeking novelty and sexual activity and emotion and that is sort of behind your ears. Your frontal lobe, which is a part of the brain that controls executive function, empathy, judgment, decision-making is in the front of your brain. Very interestingly the way that the brain builds the connections between these many regions is going to the back of the brain to the front. So it takes many years for the whole brain to be sort of connected to itself and to fully develop. The brain takes toward half decades to fully finish developing and since it is developing from back to the front the last place to fully connect is your frontal region. It is just that they're getting signals from the back the impulses the brain first click It is to sort of serve as a decision-maker and say we need to control the impulse. Unfortunately since it is not connected fully teenagers can take a lot of risks that they don't have that feedback from the frontal load working in split-second time. They do have a frontal lobe but it doesn't have the connections that are working at full speed. They have to be insulated so that they can conduct really fast because it is like electricity. We have a natural substance and that takes a really long time to wrap around all these connections. That is the thing that the last place to really get fully connected with these insulated fibers is your frontal lobe. Why would be involved in such a way that our brains develop in that order where it is hard for us to make that rational choices early in our lives? Science has not figured that out so a little bit a speculation is that the first couple decades of your life you are building your brain. Your brain is being molded by your experience and the connections that that you use the both get formed to be the most strong. So the brain needs to use experience to grow so there are many people that believe that this heightened novelty seeking behaviors as a way for the brain to get as much experience as possible during the formative years. Teenagers are not adults with fewer miles on them. They look like adults and they were there close sometimes but their brain is far from done. It is about 80% of the way there. Another interesting point is that the team brain can learn faster than adults and children also can learn faster than adults because our brain cells are connected to each other by something called synapse and the more you use these connections for one brain cell to talk to the other the stronger they get. Children and adolescents can build synapses faster than adults. That's why their memories are actually better than ours and it teenagers need to know that. They should know that they have these opportunities. You just mention the fact that teenager brains are still developing and a way that they develop makes it easier for them to learn quickly. What is the connection between that ability and teenagers to vulnerability to addiction It could be made stronger by experiences I use. So it can imprint on good things but they can imprint bad things. One is not just like repeated exposure to a a motor skill or memorizing list of vocabulary words or something a teenager can learn those faster repeated exposure to a drug can cause stronger synaptic connections than adulthood. It turns out that is a mechanism for addiction. Addiction is simply a form of learning that they have shown that. It is just in a different part of their brain. All of this research on the way teenagers brains develop in the way that that affects her behavior how much should we act on those test this new knowledge on the way schools are set up on the way we parent our children or government approaches the rights that teenager should have? So much of this information has only came out in the next decade. It is so applicable to society in many different ways. With respect to the justice system I've spoken at a number different venues about how do we think about adolescence in the criminal justice system given that they are risk prone and they don't have the neurobiology to inhibit their impulses. We did get the Supreme Court to agree that there should not be a mandatory for instance if a person under the age of 18 committed a major crime like a murder that they would at least get a chance to be evaluated to see if they could be rehabilitated. That was neuroscientists, Dr. Frances Jensen speaking with Michael Lipton -- Lipkin.

There may be a scientific reason why teens are known to be moody, impulsive and prone to sleeping in late.

Research shows our brains don't fully develop until our mid- or even late-twenties. The frontal lobe, which is in charge of impulse control, judgment and empathy, isn't completely insulated for teens, which means the electrical messages it sends don't travel as quickly as signals from insulated areas. Teens have split-second access to areas of the brain involving emotions and novelty, but not their frontal lobes, according to University of Pennsylvania neurologist Dr. Frances Jensen.


Jensen has written about this work in her book, "The Teenage Brain: A Neuroscientist's Survival Guide to Raising Adolescents and Young Adults." She is one of the main presenters this week at the Society for Neuroscience's annual conference, held this year in San Diego.

Scientists haven't completely figured out why our brains develop this way, but Jensen said it could be because our brains are molded by our experiences while we're teens.

"The brain needs to use experience to grow," Jensen said. "So there are many people who believe this heightened, novelty-seeking behavior is a way for the brain get as much experience as possible during the formative years."

Jensen joins KPBS Midday Edition on Tuesday to discuss other ways teen behavior is influenced by brain development.