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Tuesday, February 21, 2017

The Adolescent Brain: Why Executive Functioning in Teens Is a Challenge

From Beyond BookSmart's
Executive Functioning Strategies Blog

By Mireya Nadal-Vicens, M.D., Ph.D.
February 6, 2017

Editor's Note: This piece is an excerpt from a longer article The Adolescent Brain: Primed For Thrills And High On Life.

Teenagers are convinced they are ready to take the reins, no longer wanting to be held back by overly-cautious adults who don’t really "get it," who don’t understand the urgency of whatever situation is brewing at that moment.

Most teenagers have learned the mechanics of the adult world (driving, using credit cards, living a life consistent with certain priorities) and are impatient to make all of the decisions - to set all of their priorities. To teenagers, they feel sufficiently mature to run their own lives.

It’s hard to understand from a teenage vantage point that they are equipped with accelerators, but no brakes—or, at least a nuanced, situation-specific set of brakes.


Evolutionarily, there is an advantage to having the juveniles of the tribe venture forth, apparently immortal, undeterred by practical considerations of safety and warmth. Those with just the right combination of pluck and courage will establish new colonies and propagate the species; those with too much exuberance—oh well.

However, we now live in a world where the expectation is that teenagers will survive to adulthood, regardless of the choices they made while feeling immortal.


Adolescent Brain Development: Executive Functioning in Teens

Neurobiologically speaking, the adolescent brain is poised for impulsivity and thrill seeking. Two separate but interconnected processes underlie this bravado. Firstly, the last wave of neurodevelopment, myelination, has yet to be completed. By adolescence, the neurons (or brain cells) have long ago migrated correctly, formed connections to their neighbors as well as those across long ranges, selected connections for functionality, and pruned excess connections.


The last step is to insulate the well-functioning neurons in order to speed up their processing even further, to finalize the connections by myelination—in other words, to prioritize speed over the ability to further modify connections. However, we myelinate our brain in phases, finalizing the brainstem before birth, but not completing the visual areas until light and vision have pruned those neurons.

By adolescence, most of the brain has been myelinated except for the frontal lobe, the center for “executive functioning,” where planning, sequencing of activities, and prioritizing long-range goals take place. Biologically, the long-range planning part of the brain is simply slower, less ‘hard-wired’ than the here-and-now-information-processing parts of the brain.

Therefore, thrills and rewards are, frankly, more thrilling and rewarding to teenagers. In part due to the slower inputs from the frontal lobe, adolescents perceive short-term rewards as more rewarding than adults, and even small rewards are experienced as larger, better, more engrossing than they are in adults. Jokes are funnier, experiences are often ‘the best,’ everything is more urgent and more intense.


The reward center of the brain is over-valued in terms of neuronal connectivity, and easily activated in a variety of otherwise underwhelming circumstances. It’s primed to be tweaked!

The reward center serves to motivate us by producing a small but powerful response to food, sex, and novel situations. Teenagers just get a whopping dose of this. Everything is worth doing because it feels so good, so right.


The brakes, or the ability to contextualize certain pleasures and to appraise the relevant risks, are simply not hard-wired yet.

The Role of Peer Pressure on the Adolescent Brain

During development, we go from mimicking or mirroring our family members, to wanting to mimic our peers. Belonging to a peer group is an important part of a sense of identity and meaning for teenagers. This period of peer influence overlaps with the period of decreased frontal lobe myelination, and decreased front-to-back long-range integration in the brain (the so-called “default network”).

It actually turns out that teenagers whose brain connectivity most resembles adult brain connectivity, are the most able to resist their peers. However, those adolescents with less integrated long-range brain connectivity are most likely to be influenced by their peers and friends to do things they would not have done or gotten involved with on their own. The ability to resist peer influence develops only as the process of brain integration is finalizing.


The Adolescent Brain with ADHD

Teens with ADHD are likely to be a bit more impulsive than their typical peers. Often, kids with ADHD have delayed frontal lobe maturation, although most catch up by their mid-twenties. A number of different interventions can help teenagers cope with learning and behavior challenges: a school system that helps kids learn self-regulation and impulse control, treatment and coaching for ADHD, and individualized learning interventions for slow processing speed can make a big difference for teenagers at risk for falling behind their peers academically.


Mireya Nadal-Vicens, M.D., Ph.D. conducts research in the Center for Anxiety and Traumatic Stress Disorders and Center for Addiction Medicine at Massachusetts General Hospital. She is also an instructor of psychiatry at Harvard Medical School.

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