Resources‎ > ‎

* Alcohol and the developing teenage brain

Alcohol and the Developing Teenage Brain


Stephen M. Taylor, M.D., M.P.H.

(Pediatrician and General, Child/Adolescent and Addiction Psychiatrist, Vestavia Hills,Alabama)


Have you ever looked at your teenage son or daughter with a mix of frustration and bewilderment and asked, “What is wrong with that child’s brain?” If you have, welcome to a very large club (our members include anyone who’s ever parented a teenager).  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.”  It’s now fairly clear: the majority of that work is not completed until at least age 25, and some parts of this childhood-to-adulthood “brain makeover project” continue until age 40!


If you will allow yourself to get in touch with your “inner geek” for a minute, you’ll see that this stuff is pretty fascinating.  Scientists have discovered that beginning around age 11 or 12, a child’s brain undergoes a period of considerable growth and development that can be divided into three processes, proliferation, pruning, and myelination.


Proliferation is the first of these processes, and it peaks around age 11 in girls, 12 in boys.  As the word implies, proliferation is simply an increase in the size and number of brain cells in a child’s brain.  At this early stage, these brain cells do not yet have a protective, fatty covering called myelin, so these cells are unmyelinated cells.  Collectively, the unmyelinated cells in the brain are known as gray matter. So proliferation is simply the increase in the unmyelinated brain cells. In other words, proliferation results in an increase in the brain’s gray matter.


The second process to occur is that of pruning.  If you’ve ever pruned the plants in your garden, you’ll easily understand that pruning is simply a process by which brain cells are “weeded out.” The cells involved in important brain pathways are preserved and strengthened, while uninvolved cells are eliminated.  Pruning is thought by many neuroscientists to have implications for guiding development and decision-making in young people, and it is believed to continue well into the 20’s.


Myelination, the last of these developmental processes, is the wrapping of these proliferated and pruned brain cells within a fatty sheath called myelin. Myelination results in more efficient conduction of the impulses that travel along the brain cells.  Myelinated cells are known, collectively, as the brain’s “white matter.”  These myelinated cells, the white matter of the brain, conduct impulses such as pain and other sensory information much faster than the gray matter, or unmyelinated cells, of the brain.  You might consider the white matter of the brain to be akin to high-speed internet access, while the gray matter is more like dial-up.  And just as we can do many more complicated things with high-speed internet access than we could with dial-up, it turns out that myelinated brain cells are also thought to increase the brain’s ability to engage in complicated cognitive processes that unmyelinated brain cells could not.  And here’s the shocker: myelination is thought to continue until age 40 – that’s right, 40!! 


So the net effect of proliferation, pruning and myelination is a decrease in the amount of the brain’s gray matter, and an increase in the amount of its white matter. The result is a brain that operates faster and more efficiently, and engages in more sophisticated processes than it could before.  Essentially, the teenage brain is becoming a “lean, mean thinking machine.”  How cool is that?


But wait: there’s more.  You see, all of these developmental processes don’t occur in all parts of the brain at the same time.  Instead, all of this development and maturation 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.  The process starts with the brainstem, which controls the most basic bodily functions (like making sure that you keep breathing and that your heart keeps beating without you having to think about it).  Makes sense, doesn’t it?   It’s a good thing that none of us (not to mention infants and toddlers) have to consciously remind ourselves to keep breathing or keep our  hearts beating in order to stay alive. 


What is distinctly uncool from the perspective of parents of teenagers is that the front parts of the brain develop last.  That is, the areas collectively known as the prefrontal cortex –  which control higher levels of brain function, like reasoning, making decisions, weighing out options, setting priorities, assuming responsibility and considering the possible consequences of one’s actions – are the last to develop.  And remember, we’re talking about a brain that has not completed most of its development until at least age 25, with full “makeover project completion” not occurring until age 40.  Is it any wonder that your 15- or 18- or even 23-year-old can still amaze (and infuriate) you with incredibly poor judgment calls and woeful short-sightedness?


Now, let’s introduce alcohol into this developing machinery, shall we?  If you consider for a moment that, of all drugs of abuse and intoxication that people use, alcohol is probably the most directly toxic to every tissue type and organ system in the body, then you might guess that nothing good will come from introducing alcohol into the developing brain.  And you’d be right.  Research conducted by L.P. Spear and published in 2002 suggested that overuse of alcohol during pruning periods may impair crucial brain functions such as memory and learning.  Spear’s work also found that there seemed to be an increased propensity for binge drinking when alcohol use was started during the early adolescent years, when pruning is thought to begin. 


Other interesting research tells us that the frontal lobes of adolescents – which we now know are very much “under construction” – are more susceptible to the toxic effects of alcohol than are the more developed frontal lobes of adults. The same seems to be true for the hippocampus, the part of the brain that controls memory.  So adolescents who use alcohol may show more impairment in functional memory and in the ability to perform specific cognitive tasks than adults.   We also know from studies of adolescent drinkers that the earlier young people start drinking, the more likely they are to develop problem drinking or even develop the disease of alcoholism.


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 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 – 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.  In fact, you have medical science on your side. (And considering the science we’ve just reviewed, 21 is actually a very liberal drinking age!)  Your teen probably won’t thank you for being so liberal and lenient as to allow her to start drinking no earlier than age 21.  But I assure you: her brain really appreciates it!






  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.