Understanding the Teen Brain

“She’s a teenager, what do you expect?” 

Why do adults say things like that? Is there something wrong with teenagers? What exactly is going on in the teenage brain? Between puberty and adulthood, people change dramatically. During this time, children mature and develop their own identity. They also become capable of living independently of their parents. This is crucial to the survival of the human species. If children never became adults capable of building their own lives and families, humans would die out pretty quickly. But be careful! The same changes tend to make you impulsive and reckless.

Growing up is a difficult process. So how is the human brain designed to navigate through this process? 

How do scientists study the brain?

Not long ago, the human brain was hard to study. To look inside someone’s skull, doctors had to use high-energy radiation such as x-rays. But this type of radiation can be dangerous in high doses. That is why doctors only used them only when absolutely necessary. And ethically, researchers can’t risk making people sick just to look inside their heads.

However, things began to change in the 1990s. That is when Magnetic Resonance Imaging (MRI) arrived. MRI machines can take detailed pictures of the brain. There is no need for X-rays. They’re safe to use, even on children. Researchers can use MRI machines to see how different parts of the brain develop and communicate with each other over time. Thanks to MRIs, brain research is expanding fast. And scientists are getting a much better idea of what goes on in the teenage brain.

What goes on in the teenage brain? 

The human brain is made up of many interconnected parts. Each of them has its own function. Different things you do—such as seeing, moving, smelling, feeling, or thinking—are run by different parts of the brain.  And these different parts need to communicate with each other to coordinate their actions.

During childhood, each part of your brain is more focused on developing than on communicating with other parts. But at puberty, the focus shifts. The brain begins to improve its communication system.

What changes in the teenage brain help this communication system? Scientists think it’s the accumulation of a white, fatty substance called myelin. Brain cells (neurons) whose wiry extensions (axons) are wrapped in myelin communicate information faster and more frequently than cells without myelin. They are also better at coordinating with other brain cells. Myelinated cells form the brain’s white matter. White matter expands during the teenage years. This could explain why teenagers are so good at adapting and learning.

Did you know?

Some of the myelinated axons in your brain can transmit information at speeds of over 400 kilometres per hour!  

However, your brain also has an unmyelinated portion. This is called the grey matter. The grey matter actually shrinks in the teen brain. This is surprising, since grey matter contains synapses. These are the structures that your brain cells use to connect with each other. So how could cutting down on the number of synapses help your brain mature?

Don’t worry, the teenage brain is not getting rid of important material. Rather, it seems to simply be cleaning house. During childhood, your brain forms synapses easily. It builds up a lot of them as the amount of grey matter grows. But the teenage brain must become more effective. It also must become more specialized. To do this, it gets rid of unused or broken synapses. This process is called pruning. The brain also strengthens the ones synapses it often uses. The result is fewer but better connections. In other words, the result is a more mature brain!

How does the teenage brain affect behaviour?

The different parts of the brain don’t all get upgraded at the same time. This helps explain why teenagers are often impulsive and reckless. The area in charge of emotions is called the limbic system. It matures early. The area of the brain that regulates behaviour and the ability to make decisions is called the prefrontal cortex. It matures much later. In fact, it’s the last part of the brain to mature. The prefrontal cortex isn’t considered fully developed until a person is in their mid-to-late 20s! Instead, teenagers process information with the amygdala. This is a part of the limbic system. It’s the reason why teenagers may sometimes have deep, complex emotions that they cannot fully control. 

Is there a purpose to this? Some scientists believe that the development of the teenage brain is an evolutionary one. For many teens, leaving home feels risky. Let’s assume teenagers’ capacity to judge risks and consequences is fully developed. Would it be as easy to get them to leave the security of their parents’ homes and explore new territories? Probably not. This may be why emotions override judgment in the teenage brain. It pushes them out of their comfort zone and into the unknown, while their brains are still highly adaptable and have lots of room to improve.

The teenage brain may not be fully mature. But it is up to great things! The potential for learning and creativity is at its peak. But so is the risk of physical injury and mental illness. But it’s empowering to understand what’s going on up there, isn’t it?