Taking Notice of The Teenage Brain


“Andrew seemed trapped somewhere between childhood and adulthood, still in the grip of confusing emotions and impulsive behavior, but physically and intellectually more man than boy … As his mother and a neurologist, I thought I knew everything there was to know about what was going on inside my teenager’s head. Clearly I did not. I certainly didn’t know what was going on outside his head either! So as a mother and a scientist, I decided I needed to — I had to — find out.”

The foregoing is an excerpt from Frances Jensen’s book, “The Teenage Brain: A Neuroscientist’s Survival Guide to Raising Adolescents and Young Adults.” So what did Jensen find out about that murky and mysterious organ, the adolescent brain? More than anything, she discovered that teenagers — their intentions, habits, and puzzling behaviors included — are really just misunderstood, after all.

Generally speaking, adolescents are perceived as impulsive, quick-to-anger, and, at times, downright insolent. Turns out, there’s good reason for this: their frontal lobes are still developing, especially the connections between synapses. In order for all of the synapses in every region of the brain to connect, they need to be insulated in a fatty substance called myelin. Jensen explains, “We have a natural insulation … called myelin … It’s a fat, and it takes time. Cells have to build myelin, and they grow it around the outside of these tracks, and that takes years. The last place to be connected — to be fully myelinated — is the front of your brain … And what’s in the front? Your prefrontal cortex and your frontal cortex. These are areas where we have insight, empathy, these executive functions such as impulse control, risk-taking behavior.”

This stage of development is essentially a double-edged sword: the brain’s plasticity during the teenage years makes for a “heightened ability to learn,” but it also makes teens more susceptible to addiction. “… Just as repeated exposure to information makes a stronger circuit, repeated exposure to substances of abuse imprints on your brain as well. It can’t tell the difference between good and bad. Addiction is a form of learning, it’s just in a different circuit.”

Furthermore, drugs and alcohol abuse can inflict more cognitive damage in teens versus adults. For instance, when the active substances in marijuana latch on to cannabinoid receptors, “These targets actually block the process of learning and memory so that you have an impairment of being able to lay down new memories … teen brain have more space for the cannabis to actually land, if you will, it actually stays there longer. It locks on longer than in the adult brain.” This ultimately can result in a cumulative drop in IQ — evidence that dispels the myth that one’s IQ score is fixed from childhood on. In fact, adolescence is a critical period in which IQ can increase or decrease (or, of course, it can stagnate).

Another important misconception Jensen refutes: teens don’t stay up late and sleep in because they’re lazy. They do it because that’s simply how their brains are wired. Jensen explains, “Their circadian rhythm is definitely transiently shifted by several hours so that their brains want to fall asleep late at night and wake up midmorning. This is actually not unique to humans, it’s the same in many other species. It goes away with adulthood. It’s as if we as adults were asked to get up at 3 a.m. every day to go to work — it’s really horrible.”

Jensen’s findings — which go far beyond this brief taste — offer invaluable insight for parents of teenagers. Ultimately, we can utilize this information in order to, “Stay connected [to our teenage children] and also be a little bit more patient.”

This article was originally published in the Spring 2015 issue of Brain World Magazine.

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