Summary: Teen Brain Not Fully Developed

Teens lack the cognitive controls needed for mature behavior. According to recent research findings, the brain isn’t fully mature until a person reaches about 25 years of age.

  • An article written by Time Magazine focuses on recent research conducted by Dr. Jay Giedd, chief of brain imaging in the child psychiatry branch at the National Institute of Mental Health. Dr. Giedd has devoted the past 13 years of his career to studying the brain growth and development in kids and teenagers. Dr. Giedd has used his research to study certain behavior in teens. Because of his research, what was once blamed on as being “raging hormones” in teens is now being seen as the by-product of two factors: an excess amount of hormones and a lack of the cognitive controls needed for mature behavior. One surprising finding that scientists have discovered is that the teenage brain grows very little over the course of childhood. By the time a child is 6 years old, the brain is 90% to 95% of its adult size. Babies are born equipped with most of the neurons our brain will ever have. Human achieve their maximum brain-cell density between the third and sixth month of gestation. During the final months before birth, our brains undergo a dramatic “pruning” in which unnecessary brain cells are eliminated. Many neuroscientists now believe that autism is the result of insufficient or abnormal prenatal “pruning”. What Dr. Giedd’s long-term studies have found is that there is a second wave of “pruning” that occurs later in childhood and that the final, critical part of this second wave, affecting some of our highest mental functions, occurs in the late teens. During adolescence, there are fewer but faster connections in the brain. The brain becomes a more efficient machine but the trade-off is that the brain is also possibly losing some of its raw potential for learning and its ability to recover from trauma. Right about the time the brain switches from proliferating to “pruning”, the body comes under the hormonal effects of puberty. Dr. Giedd’s best estimate for when the brain is truly mature is 25 years of age. For parents, Dr. Giedd says that it might be more useful to help teens make up for what their brain still lacks by providing structure, organizing their time, guiding them through tough decisions (even when they resist) and applying plenty of patience and love.1

1What Makes Teens Tick?, Time Magazine, May 2, 2004, pp. 1-8.


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