Understanding the Teen Brain



Q: Since my daughter turned 13 last year I don’t know what has gotten into her. She is so impulsive and moody. It is almost like she’s become a different person. Why is this?


A: Parents often wonder about what makes teenagers do certain things – talking on the phone constantly, sleeping too much, or just being difficult. Understanding such behaviors requires an understanding of the teen mind and the context in which this mind develops. 


Doctors used to think that brain development stopped sometime early in childhood. However, we now know that brain development continues well into the 20s for most people. This means that even though many teens may look grown up on the outside, their brains do not yet work like an adult brain. 


Researchers have found that among the last brain circuits to form are those that run to the forefront of the brain, the prefrontal cortex, where key decision-making is thought to take place. This may be why teenagers often seem to act in emotion-driven irrational ways. They simply don’t have all of the connections to the decision-making part of the brain that adults do. In addition, teens haven’t had certain life experiences yet that can help their decision making. 



Q: My teenage daughter is so impulsive and hard to reason with. I’m really worried that she may make some wrong choices about drugs, alcohol and sex. What can I do to help her get through her teen years?


A: Because of how the brain develops, it is natural for teens to be impulsive and lack the reasoning ability of adults. However, such biological explanations should not be mistaken for excuses for teenagers to act without limits. We are all more than the sum of our parts, and social and cultural forces have powerful influences in helping teens regulate and develop controls over their behaviors. 


Teenagers watch adults around them for cues on how to act and behave – a fact that has been confirmed by both psychological and sociological research. Teens are modeling their behavior on what they see in their peers and adults. Simply put, as parents and concerned adults, we need to act in ways that will help shape the kind of persons we hope our children will become.



Q: My teenage son has such a hard time getting up in the morning for school. Could he be depressed?



A: Sleeping a lot is indeed a common sign of depression, but it is also common teen behavior. Teens need more sleep than adults because their brains and bodies are developing so rapidly. In addition, some researchers now think that the way our brains develop during our teenage years may create a natural shift in sleep patterns toward staying up late and sleeping in.



Since untreated depression can have serious consequences, it is best to err on the side of caution and call your child’s primary care doctor with your concerns. He or she can screen your son for additional signs of depression and refer your son to a specialist in adolescent mental health, if necessary.


Niranjan S. Karnik, M.D., Ph.D., is a physician at the Palo Alto Medical Foundation’s Fremont Center Department of Psychiatry and Behavioral Health. Advice is not intended to take the place of an exam or diagnosis by a physician.