Skip to content

The Teenage Brain – What to Know

Just like anyone who has raised children through adolescence, I have occasionally stood, scratching my head and looking at my kids after they’ve said or done something I found exasperating, and wondered, “What is wrong with that kid’s brain?”  If you have too, I have a possible answer for you.

The good news is that nothing is wrong with the typical teen’s brain that another decade or so of development and maturation won’t fix. An emerging body of research into brain development suggests that the adolescent brain is very much a “work in progress.”  And it’s now fairly clear: most of that work is not completed until at least age 25, and the final “finished product” is not done until age 40.

Consider the following:

  • Beginning in the preteen years, the brain undergoes a period of considerable growth and development which can be divided into three specific processes: proliferationpruning, and myelination.
  • These developmental processes consist of an increase in the size and number of uncovered brain cells (proliferation); a weeding out of the unnecessary brain cells (pruning); and then a covering of the remaining cells (myelination) to turn them into the “white matter” of the brain, which conducts brain messages more efficiently.
  • With the expansion of white matter comes a greater capacity for sophisticated brain activity. So you can think of this developmental process as turning the teenage brain into a “lean, mean thinking machine.”
  • All of this proceeds along the landscape of the brain in a predictable “back-to-front” pattern.  The parts of the brain located in the rear develop first. These are the parts – like the brainstem– that tend to control more basic and less sophisticated (but essential) functions like keeping you breathing and keeping your heart beating without you having to think about it.  The parts that control higher levels of brain function are located primarily in the front – the frontal lobes – and they develop last.  These are the structures that control functions like reasoning, making decisions, weighing out options, setting priorities, assuming responsibility and considering the possible consequences of one’s actions.  Remember, the bulk of this isn’t complete until at least age 25, with the full “project completion” not achieved until age 40 – that’s right, 40!

Keeping all of that in mind, here’s what we know about introducing alcohol and drugs into this developing brain…

  • Youngsters who start drinking alcohol, using addictive prescription medication, or illicit drugs during the early teen years – which is when pruning is occurring – are more likely to engage in binge drinking and developing a dependence to the dug in use.
  • Such heavy use of alcohol and drugs during that same period may render kids more susceptible to the damaging effects of alcohol drug use on learning and memory.
  • The earlier young people start drinking and using, the more likely they are to develop problem drinking or even develop the disease of alcoholism or drug addiction.

So what do we make of all of this? It’s simple. Your teenager’s brain is still very much “under construction” until long after she becomes an “adult.”  Introducing alcohol and drug usage into this complicated developing machinery is, at best, a bad idea.  So don’t be afraid to lay down the law to your teen: “NO alcohol, NO drugs – not even one drop – until you are at least 21 years old! NO exceptions – not even at weddings or on New Year’s Eve!”  Go ahead.  You’re not being unreasonable or extremist.  In fact, you have medical science on your side.  (Actually, when you consider the science, you realize that 21 is truly a “liberal” and “lenient” drinking age!) Your teen may not thank you for being a stickler for the “lenient” drinking age of 21, but her brain will really appreciate it!

– Dr. Steve


  1. Herrman, J. (2005). The Teen Brain as a Work in Progress: Implications for Pediatric Nurses. Pediatric Nursing, Retrieved December 30, 2005, from
  2. Miller, M. et. al. (2005) Adolescents and Binge Drinking: A Clinical Approach (Archived Web Conference). Retrieved January 2, 2006, from
  3. National Institutes of Mental Health (NIMH). (2001). Teenage brain: A work in progress. Retrieved December 18, 2005, from
  4. Spear, L.P. (2002). The adolescent brain and the college drinker: Biological basis of propensity to misuse alcohol. Journal of Studies on Alcohol,63 (2), 571 – 582.