It turns out that the adolescent brain undergoes a major reorganization. One of the primary ways this happens is via myelination, or the process of sheathing the axons of the nervous system to speed the process of communication in brain networks. But changes in amounts of grey and white matter, changes in neurotransmitter levels and alterations of neural circuity are also part of the process. It’s important to remember that these changes reflect sophisticated refinements affecting complex decision making and emotion regulation that will prepare the young person for life as an adult. Understandably, this takes time and the course of brain development is shaped by the particular context and experiences the adolescent encounters. Some parts of the brain will not be fully myelinated until the mid to late 20’s. The parts that take more time to develop function to control higher order planning, organization and cognitive control. In contrast, emotional centers in the brain (e.g. amygdala and associated regions) mature in early adolescence and exert their strong influence over cognition and behavior while the higher-order control centers of the pre-frontal cortex are still developing.

Researchers hypothesized that the adolescent brain was in a state of imbalance and that this was the reason adolescents are more prone to impulsivity, thrill-seeking, risk-taking (especially with peers). However it’s important to remember thar this developmental trajectory can also play a useful role, because some risk taking (like trying out for sports or for the debate team) is adaptive and important for learning.

Adolescents are also prone to more frequent and intense episodes of distressing emotions. Brains at this time register negative emotions quickly and respond more strongly to unpleasant experiences than at other life stages. In contexts that could be challenging, the developing adolescent brain has less well-developed resources for cognitive control. This improves in general over the course of adolescence. The red arrow in the figure shows how impulsivity peaks in adolescence and declines thereafter while cognitive control (illustrated by the blue line) increases linearly over adolescence and into adulthood.