The Teen Brain

Important changes take place in the developing teen brain. While a child of age 5-6 years already has 90% of the adult brain, around the ages of 11-12, for example, important developmental changes begin to occur in terms of pruning and reorganization that continue through the teen years and into the early 20's.

These important changes enable the teen brain to make more complex choices under stressful conditions by utilizing a broader range of various parts of the brain. When pressed with complex choices under time and pressure, the immature teen brain becomes overloaded. S/he makes poor choices under these conditions, which can lead to disastrous results. Usually, these poor choices are compounded by cascade of additional poor choices.

We as adults look at these choices in frustration and awe. How could they make so many stupid decisions? The lament of many a parent in their teens growing up years. We think they must have been brain dead when they made these decisions. Maybe their brain took a vacation?

The irony is that the teen's brain was really hard at work, just overwhelmed. These complex decisions are made primarily in the prefrontal lobe:  Prefrontal lobe

The problem is, that is all s/he is using!

In the mature adult brain, under complex, stressful conditions, more and more parts of the brain are brought into play and utilized. In the maturing teen brain, however, these additional pathways are not available.

It is this region of the brain that is responsible for the so called executive functions, i.e. task organization and planning and decision making.

This is not to say your teen has an excuse for his or her "stupid" choices. Because of their inexperience and limited logical circuitry (or so it seems their logic circuits must be limited), they tend to put themselves into situations that become stressful and overwhelming.

For example, the teen driving down is talking on her cell phone, maybe following to close behind the car in front. That car in front slams on its breaks, your teen is momentarily distracted, looks up and sees the car coming up fast. Instead of swerving or taking appropriate action, she shuts down, takes no action, and, "wham!" slams into the other car.

Studies using functional magnetic resonance imaging (fMRI) show that when teens perform a complex decision-making task, his or her brain (perfrontal lobe of the cortex) is working much harder than in an adult's brain. Additionally, or maybe because of, while an adult uses additional regions of the brain under such stressful situations, the teen doesn't or can't yet.

If we use a computer as an analogy, in stressful, complex decision making situations, a teen is eating up usable memory like crazy. Adults, on the other hand, are able to call on additional memory to handle the same situations. Adults call in other parts of the brain to collaborate and distribute the work load.

Self-Control Challenges

These executive functions/prefrontal cortex differences between teens and adults can also help us understand teens' difficulties with self-control.

There are two basic types of behavioral controls operating in our brains: exogenous and endogenous. Exogenous controls are automatic, also referred to as "reflexive" (as in reflex). For example, how our pupils of our eyes contract when exposed to a bright light. Endogenous controls are voluntary. They originate from internal programming or effort. In our bright light example, a conscious decision not to look at the bright light is an example of endogenous controls.

A mature adult prefrontal cortex can easier override exogenous controls with endogenous controls. Teens have a much greater difficulty doing this because of their not yet mature prefrontal cortex.

This means when it comes to impulses, adults can control these easier with endogenous controls, especially in stressful situations. Again, the teens prefrontal cortex, which must tell the rest of the brain what to do, can become overloaded and overwhelmed in stressful situations. S/he simply runs out of available memory capacity to solve the problem or restrain the impulse.

Pruning Continues

Structural MRI studies (look at structure of the brain) show that the adolescent or teen brain undergoes significant physical changes during these years. These regions are the prefrontal cortex that control impulses, decision making, behaviors--in short the executive functions.

These physical changes involve two primary mechanism: myelination and synaptic pruning, both of which increase the brain's transmission efficiency.

Synaptic pruning involves degrading or reabsorption of little used or unused synapses. Synapses are the interconnections between nerve cells the neuron

Myelination involves putting more insulation (myelin) around the transmission lines of the neurons.The more insulation, the faster the nerve impulses can move.

Better Parenting, Not Meds!

The drug companies would like you to think there is something wrong with the teen brain that needs to be "fixed". And, of course, what fixes them is their pill. This is just normal brain development. It is not something that needs fixed or is broken.

So, parents, read the two parenting sections of the website on parenting basics and empowering parents, and references therein. What is needed is good parenting, not drugs. Don't be afraid to ask your teen what, where, when, how, and who with. Set boundaries and curfews, and enforce them. Talk to your teen, not at your teen. Don't be afraid to say, "No," and stick to it. Etc....


  • Ronald E. Dahl and Linda P. Spear (editors). 2004. Adolescent Brain Development: Vulnerabilities and Opportunities. Annals of the New York Academy of Sciences, Vol. 1021: .
  • Sabbagh, L. 2006. The Teen Brain, Hard at Work. Scientific American Mind August/September: 20-25.
  • A. D. Schweinsburg, B. J. Nagel and S. F. Tapert. 2005. fMRI Reveals Alteration of Spatial Working Memory Networks across Adolescence. Journal of the International Neuropsychological Society, Vol. 11:631–644.
  • P. Shaw et al. 2006. Intellectual Ability and Cortical Development in Children and Adolescents. Nature, 440: 676–679.



Neurogenesis and Healing

Addiction and the Teen Brain

The Triune Brain

State-Dependent Memory, Learning, and Behaviors and Trauma

Basic Genetics Series

Nature and Mind

  • Clinical Psychobiology