The Amazing Teen Brain

(whoosh and beeping) (electronic music) – I tend to get unsolicited feedback, such that should be a very short talk. (audience laughing) Isn't that a contradiction of terms. You mean they found one. (audience laughing) And there's like a book a month that sort of piles on these unflattering portrayals, The Primal Teen, that's actually not too bad, but Mom, I Hate You, Get Out of My Life, But First Drop Cheryl and I at the Mall. Now I Know Why Tigers Eat Their Young is right to the point, Yes, Your Teen Is Crazy. But with the technology such as magnetic resonance imaging, we can for the first time look under the hood of the living, growing brain. And what we've found is that not only do teens have brains, (audience laughs) but they're good brains, they're as they should be, they're not broken.

And I'd go so far as to say if they weren't the way that they are, we wouldn't even be here. And evidence from that comes from kind of unlikely source I'll get to in a minute. So the teen brain's different than the brain of a child, it's different than the brain of an adult, it's not just half way between, it's kind of its own distinct entity, and it's been exquisitely forged by evolution to have certain features. Behaviorally, the big three are increased risk taking, increased sensation seeking, and a move away from parents to peers. And I think these are deeply rooted in our biology, because it's not just humans, all social mammals have these three features. And so we're probably fighting Mother Nature by trying to eliminate these. And this is always very speculative to argue these ways, but one idea is that it helped us get out of the home, which is a really irrational thing to do, okay, Why, people loved us, they feed us, protect us, it's a good gig, right? But it turns out it works better if we do.

Less inbreeding, it just sort of, you know, morally, right around, it just works better if this happens. And so these features, they involved at a time without firearms, without high-speed motor vehicles, without designer drugs and stuff, so some of these issues are kind of this stone age brain in computer age world aspect. But I think that these behaviors have virtues as well. When I was at the NIH, the Smithsonian Museum, sort of close, they had this exhibit, the Hall of Human Origins, which I really liked, but kind of not strictly featured a little placard on the floor, looked at the relationship between brain size and climate change. And the last big increase in brain size 500, 800,000 years ago. But what I thought was intriguing was that what was correlated was the change in climate, not the degree. Before seeing this I thought, yeah, it got really cold, you had to be supersmart just to stay alive long enough to get food and reproduce.

But this is subtlety different. Everybody in this room had ancestors whose brains were good at adaptation. And we're really good at it in terms of, even compared to our quite close, genetically close, rather in the Neandertrumps, or Neanderthals, (audience laughs) I'll pause, we can edit that later. (audience applauds) We can tell enormous amounts from teeth and fossilized teeth, which actually we've done it. Everybody's teeth right now are fossils, calcified cells. But they work like trees so they have rings. So tree rings, this was a wet year, a good year of growth, the rings are wider. And across many different species, the rings get closer and closer as you mature. The rings stop and you're done growing, it's done maturing. And so when you find these fossilized teeth, if you find a fossilized Neanderthal tooth of a 12-year-old, and then check the rest of the cave, he's gonna be with his children, not his parents. And this is often portrayed as surprisingly rapid growth in the Neanderthals. But I think that's the wrong way to look at it. What's surprising is our protracted growth.

We're the outliers, by far, it's one of the most distinctive things about us. And even across like crows and many other species, the longer you're under protection of your parent, the more complicated your food gathering, your communication, problem solving. Crows are actually really smart as an example. But similar crows, in size and, that don't have this protected maturation, don't have those abilities as well. It doesn't work to just keep your kids at home until their 40. I don't think on an individual basis it doesn't work, but it's an intriguing trade-off I think that we keep options open, we keep our brains changeable, see what the environment's gonna be like. We can live on the North Pole, we can live on the equator, or everywhere, we can even live in outer space for a little while with technologies that have been developed. And so this is a good thing, I think, in terms of this ability to keep options open for a long time, but it's really being put to the test with the digital revolution. And this is, just in my short career is a game changer.

The way that we interact with like what we're doing at this moment with ones and zeroes and the lights, the projector, it's changed everything, it's changed the way that we learn, content that's on internet and the greatest minds on the planet are a click away, you know, for free. It's just amazing, it's magical. The way that we play and the way that we interact with each other. And so I've been fascinated by this interaction in terms of the biology of this changeability and the technologies that have taken over in a sense, so, of almost 11 hours a day of screen time, and 30% of that time more than one device. And so the usual question is is it good or bad or that's the wrong question, right, almost any interesting question is it depends in terms of in what ways and how it depends and what it depends upon.

But I think that this is an opportunity in terms of to influence adolescents. One of the tragedies of my profession is that it's almost a 10-year gap between onset of illness and treatment. We need to do better. And I think perhaps the technologies can help us get there in terms of by monitoring things like social media activity, maybe even just movement, GPS data, harnessing these technologies in an ethically appropriate way to help us recognize mental illness so that we can intervene while the brain is still more changeable. And so a lot of the debates around this that there's it's just not natural, right. We evolved to talk to each other, to be with each other, to share smiles and touches and every, and now we're looking at screens for a big part of the day. But a kind of argument to that is reading's not natural either. Reading's only about 5,200 years old.

So most humanity, nobody read. So I don't think that by itself is a good argument. It kind of makes the point that the whole aspect of this is the changeability. 10,000 years ago hunting, gathering berries, it's the same brain in terms of that's a blink of an eye in evolutionary terms. But our brains are amazing. We can adapt, you know, a lot of us spend a lot of our day with symbols, you know, words, and that's so different than you know, what our ancestors did. And so my career's basically been this in terms of trying to understand this plasticity in terms of how to optimize the good and minimize the bad. And this kind of, how do you help people with mental illness is the fundamental question. And so kind of that notion of like what do we know? How do we know what we know? What don't we know? Why don't we know? That, but, you know, my first assumption is the brain's involved. I hope so.

It's like a spleen or something, I'm gonna feel like a complete fool down the road. But I think, you know, it's a reasonable assumption. And professor Jernigan began this journey, B.J. and I started together at NH and following down that path of looking at the brain, and how the brain changes in both typical development and in illnesses. It's kind of a noncreative, started to design, actually, but scan kids, you know, when they're young and follow them as they go through life, see how they're doing at school, at home, see what sort of influences on the brain for good or ill. And at the NH, we did about 10,000 scans of half the kids healthy, half the kids with different illnesses. And what we found were, it's nuanced, but like the brain doesn't mature by getting bigger and bigger.

By first grade it's already 93% adult size. It matures by being more connected within itself and more specialized. And this idea of being more connected, there's many ways you can approach this, but white matter is one of them. So, this insulating material that you get one to 2% more of into the fourth or fifth decade, the brain is able to communicate amongst itself faster. It's not very subtle, it's like 3,000-fold increase in bandwidth I think underlies a lot of the remarkable behaviors that we can do. But it's not just a matter of maximizing speed, it's all about the timing. And so the fire together wired together the meaning, the information's in these patterns. But more and more we're understanding that that's the progression. If we look at different parts of the brain like letters of the alphabet as you go from an infant to child latency, teenagers, emerging adulthood, that these letters become words, the words become sentences, the sentences, you know, paragraphs, metaphorically. And this all goes up in adolescence.

The brain, no matter how you measure it, whether the molecular, EEG, blood flow, it becomes more connected. And this is kind of a fresh look in terms of this idea of Graph Theory Networks, it gives us a whole new look. So, for something like schizophrenia, before we'd be like, is this chunk bigger or smaller or different shape or size? But looking at the same MRI scan, the same data, and looking at how it's interconnected, then we can discern old from young, healthy from ill, 'cause their brain, not perfectly, but it's really exciting for someone like me I can't do the math, but to be a consumer of it in terms of that, by looking at this connectivity, it gives us a whole new perspective on these illnesses. The other processes, the gray matter process and the one-two punch is overproduce and then war, or fight it out. It's almost all complexity in nature arises, engine of evolution, overproduce something nonrandom selection. And it has great potential.

So it's constantly on-going, it's not like you only overproduce during childhood and only prune during adolescence, but that we see this upside down U-type of curve where as we specialize, the brain actually becomes smaller. So after around 10, 11, 12, your brain doesn't get bigger, it gets smaller, but leaner, meaner, more specialized based on what you're demanding of it. But it's not all parts equal. The prefrontal cortex involved in controlling impulses, long-range planning, it's particular late to settle down. Some, you know, 25 to 30, and that combined with the hormonally-activated, puberty-activated limbic system, the passions of words, this imbalance creates a lot of the specials of teen behavior aspects. But again, this is how it should be, if the prefrontal cortex is already done like 11 or 12 and stuff, then we wouldn't be as adaptable. And so I think this is the tension or the trade-off. The other place to start in terms of that is illnesses happen at different times. Not perfectly, there's always variation, but Alzheimer's doesn't happen when you're three, and autism doesn't start when you're 60, that characteristically certain illnesses tend to emerge at certain ages. And that's puzzling, you know, why is that? In terms of.

And when you start looking at this, so much happens in adolescence, not a lot, most. It's up to 75%, and I still don't know the answer, that's been for 25 years, and we're like why? Because the early answer is oh, teenagers are stressful, it's a stressful time of life. You know, kids have their parents killed in front of them, or they're starving to death or there's war in 20 countries, enormous stresses, but they don't get schizophrenia. And so that never rang true. And I still don't know the answer to this, why do things happen when they do? And so just one example is for schizophrenia, all of the findings you see in adult schizophrenia, you can predict what if typical teen changes went too far? It's not causal, they already had schizophrenia, but so far without exception, in terms of both the MRI changes, but also the molecular changes, and so it's just this point, it's intriguing. It doesn't help me help families with schizophrenia, but I think these are the kind of clues that we're starting to understand. So, in this specialization process, in typical development, it's about 7% from ages 12 to 17, in schizophrenia, 28%.

So it's not subtle. You know, four-fold difference. And so, understanding the typical development, I think, is key, but about half of what I deal with as an analyst isn't illness. All right, pregnancy is not an illness, but it's a big deal. Relationships, car accidents, incarcerations, you know, life decisions, this happens during adolescence. And it's frustrating as a physician, it's like there's no insurance forms to check in terms of for these very real issues that aren't an illness. And this kind of notion is the glass half empty or half full? Because this changeability could be a great opportunity, making it even more tragic that we aren't recognizing the illnesses when they occur. And my final sort of analogy is to use Michelangelo in terms of this is a very famous painting of his that by design should look like a brain, a cross-section of the brain, he, no, he wrote about it himself and stuff, and it's sometimes called the original synapse, you know, the.

(audience laughs) But it's not like that, it's much more like his other expression of art, sculpting. We start with this block of marble, and life experiences and so, then we eliminate part. So we might be born with different chunks of marble, sizes from genetics, you know, but within each, if we knew what we were doing, if we could guide this process, you know, there's masterpieces. And you know, I think almost everybody. We don't know very, we don't know what we're doing yet very well. And it's like most of the illnesses emerging less than 1-1/2 % of the funding has been adolescence, until now finally, now, we have this project, that for the first time is going to really do this right. 11, 12,000 kids, 19 sites across the country to understand what matters. How does the brain grow in health and illness, looking at, you know, everything we can think of, frankly, in terms of influences on this. I'm gonna brag for San Diego a bit in terms of there's these 19 sites across the country, but the coordinating center for the quantitative core and the neuropsyche core coordinating all the centers are both here in San Diego as well.

What a good deal for us, you know, in terms of the opportunities to try to understand what matters in teens' lives. And so the technologies is a big part of it, how can we get a better sense of internal and external environments with the sensors, with devices they're already using, already wearing. 'Cause this is the crossroads in life. This is where people make big decisions about their direction in life. And there's this kind of notion that teens are messed up and they're misguided and stuff, and it's dangerous. And I feel bad, 'cause I've, (audience laughs) Oh, I see. I don't know, people will be honest with me. But this is in the crossroads. And what happens is even teens themselves buy into this, right? And like stereotype, thread and stuff, if you think that you're, you know, not capable and stuff like that, it matters.

Most teens do well, you know, they'll get through this, they'll do well. But I think we do a disservice by selling them short and I think that we really need to recognize the huge upsides of this, much more than the downsides that if we can figure out what we're doing, what matters, we can really make a big difference. Thanks. (audience applauds) (electronic music).