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Child and adolescent brain development: Here's what you need to know

Here's what you need to know about your child's brain development.
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The noggin, the noodle, the brain: no matter what you call it, understanding it – and the way it changes throughout a child’s development – is one of the most important parts of parenting.

Parents often want a quick answer – preferably before someone starts crying (and we’re not just talking about the children). But when it comes to the brain, there’s a lot to learn, and even the experts don’t have it all figured out. “If the brain is five miles, we might understand five inches of it,” child and adolescent psychiatrist Dr. Dan Siegel says. But, those “five inches” we do understand are pivotal for how we help our children realize their full potential.

Early brain development

The human brain has approximately 100 billion – give or take a few billion – neurons working to process and transmit information every second of every day. And while we’re born with nearly all of the neurons we’ll ever have, there’s still a lot more development to come, child and adolescent psychiatrist Dr. Jess Shatkin says

“Throughout the first decade of life, our neurons (the gray matter of our brain) grow and grow in a relatively undifferentiated manner,” Shatkin explains. In fact, according to Center on the Developing Child at Harvard University, “in the first few years of life, more than one million new neural connections are formed every second through the interaction of genes, a baby’s environment and experiences with adults.”

The importance of these early neural connections cannot be understated. After all, they set the tone for how the baby will come to understand and navigate the world. While the baby might not have conscious memory of this time in their life, their brains will. So, it’s important to nurture newborns with love, care and stability, so their brains can build on that foundation and develop in the healthiest way possible. This continues into the early childhood years as that foundation is built upon through exploration and new experiences.

While the young child’s brain is growing at an exponential rate, it’s more concerned with breadth – taking in as much information as it can – than depth – deeply analyzing and prioritizing that information. And this makes intuitive sense. After all, how else could a child learn so much – how to walk, talk, read, ride a bike and add numbers – in so little time? The brain “doesn’t know yet what its ultimate purpose will be, so it keeps its opens open,” Shatkin says. But once a child hits puberty, the brain undergoes another major change, switching gears to focus on depth so it can figure out just what that “ultimate purpose” will be.

Adolescent brain development

There was a time when scientists believed that the teenage brain functioned largely like an adult brain, only a little less refined. But breakthrough research has actually proved quite the contrary. The teenage brain is “profoundly different from the brain of either a child or an adult,” neurologist Dr. Judy Willis says. But why? It starts with a process called myelination.

As a child reaches adolescence, myelination begins shifting the brain’s focus from quantity of connections to quality of connections. Instead of acquiring many different connections at random, the brain begins streamlining the connections it already has: reinforcing the strongest, or most often utilized connections, and removing the weakest, or least often utilized connections, making the neural pathways stronger, and the brain more efficient, Shatkin says. This process is commonly referred to as “pruning.” Just as a gardener needs to prune away the dead or damaged stems in a rose bush in order for it to grow, the brain needs to prune away weaker connections in order for it to reach its full potential.

While the brain is undergoing myelination – streamlining and strengthening its frequently used connections – something else is happening: it’s hardening, Shatkin says. This process is marked by an increase of white matter, or myelinated (pruned) tissue, and a simultaneous decrease of gray matter in the brain. It’s also why picking up an instrument, or learning a second language, is so much easier when you’re a child: your brain is more adaptable and flexible, having yet to be hardened by the process of myelination.

So while the brain is becoming more efficient, it’s also becoming increasingly rigid. But that’s not all: the brain’s reward preferences are also changing during adolescence, leading teenagers to seek more pleasure, and yes, take more risks. Why? Well, it has a lot to do with a little chemical we all know (and love, whether realize it or not): dopamine.

Dopamine is “an essential neurochemical that, among other things, helps us learn,” Shatkin says. Its job is to “focus our attention on what’s potentially pleasurable, thereby helping us to learn about what really matters for our survival.” And if you have a teenager – or remember being one – you might not be surprised to know that we’re “more responsive to dopamine during adolescence than at any time of our life,” Shatkin says. So what ends up happening? The increase and sensitivity to dopamine causes teenagers to “become biased in favor of selecting the action with the highest potential for reward,” and therefore more likely to take risks, Shatkin says.

Here’s the thing: myelination and brain development doesn’t happen all at once. Instead, it works in stages, starting in the back of the brain with “evolutionarily older and more primitive functions like vision and movement,” Shatkin says. That means the parts of the brain responsible for physical movement and coordination will be “well myelinated and networked by age fifteen to sixteen.” And this anecdotally makes sense. As Shatkin says, “[This process] is why we begin to see some terrific athletic performances in this age range, and why I first lost a running race to my son when he was fourteen years old.”

Another part of the brain that matures earlier in children? The limbic system, or the emotional center of the brain. “The job of the limbic system is to produce emotions like love, envy, rage, irritation, happiness, and desire,” Shatkin says. From an evolutionary perspective, this early development also makes sense. “It is these emotions that drive our behavior toward the things that matter for our survival, such as eating, procreating, and defending ourselves,” Shatkin says.

On the other hand, the newer, more advanced parts of the brain – the frontal lobes – are the last to myelinate. Most notably, the front of the frontal lobe, the prefrontal cortex, often referred to as the brain’s CEO, might not fully develop until a person reaches their mid-twenties. While the limbic system drives our emotions, the prefrontal cortex “guides our planning, organization, memory, attention, and decision making,” Shatkin says.

Here’s one of the most important takeaways to remember when it comes to dealing with teenagers: emotions develop before logic. And the bridge between these two functions doesn’t fully link until we’re older. As a result, “humans are genetically engineered to prioritize emotions over logic in our adolescent and early adult years,” Shatkin says. Cue your angsty middle schooler.

The process of adolescent brain development might explain some of our frustrations with teenagers. By the time they’re in their mid-to-late teens, they may start appearing more mature – armpit hair and all – but in reality, the most advanced part of the brain might have another decade to go until it’s fully developed. But this doesn’t have to be a challenge. In fact, it can be incredibly exciting. After all, a teenager’s brain is literally working to figure out who – or what – it will be.

The key? Allow your adolescent to take the lead – and even veer off “the path” from time to time. If adolescents aren’t given the opportunity to take healthy risks and learn to make decisions for themselves when their brains are undergoing this life-defining development, they’ll have a harder time building these skills in the future.

Knowing how the brain works can literally change a person’s life. As a parent, it can help you guide your adolescent through their development and understand their sometimes erratic – or confusing – behavior. As a child, it’s comforting to know that these changes and feelings are completely normal, and in fact, a rite of passage. But for all of us, appreciating the power of the brain, and our capacity to continuously learn, can set us for a lifetime of growth and exploration.