If you have ever wondered why the teenage years are so difficult for parents (and often the teens themselves) you need look no further than their brain. The brain undergoes rapid and profound development during the teen years, much more so than during most of childhood. It is a time when the areas of the brain involved in the calculation of risk, rewards and decision making go through increasingly major changes. This may explain why late adolescence (between ages 15 and 19) has a six times greater mortality rate than those in late childhood and early adolescence (between ages 10 and 14).

Research conducted by scientists using magnetic resonance imaging (MRI) from early childhood through adulthood has mapped the many changes that the developing brain makes as it matures. They have found that the brain continues to develop into a person’s early 20s, with the frontal lobes that are responsible for reasoning and problem-solving being developed last.

Although the teenage brain is more impulsive and willing to take risks, it is also dynamic, vulnerable and stimulated by positive feedback. The reason for this is that the reward centers in teenage brains are highly responsive, while at the same time, the region of the brain associated with self-control is still not developed fully.

Dr. Jay Giedd, Chief of Brain Imaging at the Child Psychiatry Branch of the National Institute of Mental Health, says “The most surprising thing has been how much the teen brain is changing. By age six, the brain is already 95 percent of its adult size. But the gray matter, or thinking part of the brain, continues to thicken throughout childhood as the brain cells get extra connections, much like a tree growing extra branches, twigs and roots.”
Although the brain grows in gray matter significantly during childhood and early adolescence, the amount of gray matter actually begins to fall in mid-adolescence, which researchers say is a normal process of brain maturation.

Giedd says, “… the pruning-down phase is perhaps even more interesting, because our leading hypothesis for that is the “use it or lose it” principle. Those cells and connections that are used will survive and flourish. Those cells and connections that are not used will wither and die. So if a teen is doing music or sports or academics, those are the cells and connections that will be hard-wired. If they’re lying on the couch or playing video games or MTV, those are the cells and connections that are going [to] survive.”

Studies have shown that experiences early in life have a profound effect on the development of the teenage brain. Researchers at the University of Pennsylvania found that children who received a lot of cognitive stimulation and parental nurturing had a brain with a thicker outer cortex, which is important in thinking and memory. Another long-term study from the Institute of Cognitive Neuroscience in London discovered that there were major structural changes in the areas of the teenage brain that relate to empathy.

Adults should perhaps give teenagers more of a break. As Giedd says, “It’s sort of unfair to expect teens to have adult levels of organizational skills or decision-making before their brains are finished being built.”