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In your teenage and young adult years, your brain is changing in important, exciting ways that scientists are only just learning about. Here are a few of them.
Scientists used to think that your brain was pretty much fully developed by puberty. But it’s become clear that’s not true.
Kate Stein, a child psychiatrist who works in Oxford, tells BuzzFeed News: “We used to think the brain was only really plastic in childhood, but actually it’s been shown that adolescence is this really interesting time.”
“There is this clear change in intellectual capacity,” Stephen Wood, a professor of adolescent brain development at the University of Birmingham, says. “You gain particularly in executive function – things like working memory and planning and organisation – and of course a massive increase in social cognitive understanding.”
Most experts agree that adolescence begins with puberty. But it doesn't have a clear ending. "People talk about the adoption of adult roles and responsibilities," says Wood. "It isn't very helpful, because nobody's quite sure what that means.
"If 400 years ago you got sent down the pits aged 14 because you needed to go out to work, does that mean you've got an adult role? You're an adult at 14?"
Roughly speaking, though, it's understood that it carries on well into your mid-twenties. "The quote that everyone uses in the field is from Shakespeare's A Winter's Tale: ‘I would there were no age between ten and three-and-twenty, or that youth would sleep out the rest; for there is nothing in the between but getting wenches with child, wronging the ancientry, stealing, fighting.’" It shows, he says, that the thought of the early twenties being "of a piece" with the teenage years goes back at least as far as Shakespeare's time.
The difference between what Stein calls the “thinking brain” and the “feeling brain” is at its starkest in teenagers, she says. The bits of your brain involved in emotion ("your feeling brain – your limbic, subcortical, emotional structures, your nucleus accumbens, all of that") are largely developed by the onset of puberty, but the parts of your brain involved in judgment and control – “your thinking brain” – are still growing. “Your prefrontal cortex doesn’t fully mature until after adolescence,” she says.
The chemistry of your brain is changing as well as the structure. “One slightly simplistic way of looking at it,” says Wood, “is that when you enter puberty you get this upsurge of sex hormones, which alters the neurochemistry.
“The way dopamine [the ‘reward’ chemical] is released in your brain changes. The way you’re sensitive to emotionality changes. All these things leave you with more drive to engage in various activities, which you don't yet have the cognitive control to resist. There’s this developmental lag between the bit that's making you want to do stuff, and the bit that's letting you say, ‘No, actually, not that stuff.’”
And that leads to young adults doing things that are riskier or scarier, he says. “Who's most likely to go on the scariest ride at a theme park? It tends to be teenagers. Who are horror movies marketed to? It tends to be teenagers.”
This behaviour isn’t limited to humans, he says. “You see increased risk-taking behaviour in non-human primates, in rodents. There's some evidence that adolescent male primates, in particular, make much longer leaps through the canopy than they do as adults. Adolescent rodents will roam further from the family nest.”
Wood says that in experiments, “young adolescents, aged 14 to 18, made a lot of risky choices when they were with peers” – many more than when they were unobserved. Older adolescents, aged from 19 to 22, and adults didn’t behave very differently whether they were observed or not.
The researchers scanned the test subjects’ brains during the experiments. Interestingly, they found that the bits of their brains that are involved in inhibition and control weren’t any more or less active when others were watching. But the bits engaged in reward – specifically, an area of the brain known as the ventral striatum – really were, but only in the younger teenagers. “The assumption is that it's just more rewarding to take risks in the presence of peers,” says Wood.
“When children are in primary school, they have social networks, but they’re fairly fluid,” says Wood. “And they’re happy to chat with adults. But once you get to be a teenager you tend to spend more of your time with a specific social group of your peers, and you spend less time talking to adults.”
It's a key time for establishing social status and hierarchies. “I think as adults we don't notice the tradeoffs that are going on,” says Wood. “Say the choice is whether or not to jump off this cliff. It's quite a long way down, you don't really know what's down there, and at the very least it might hurt if you misjudge it. So there's a clear physical risk.
“But at the same time there's a social risk. Not doing it will mean you lose face in front of the people who are egging you on. And it may be that what's more important to me is the social risk. I'd much rather have a broken leg than be isolated from my peer group. And adults don’t see the social risk, so they say, ‘This is weird behaviour, it makes no sense.’”
“There's good evidence that puberty triggers a change towards an evening preference,” says Stein. “Teenagers naturally want to go to bed later and wake up later. On a biological level that's pretty much proved.”
Wood agrees: “In mid-to-late adolescence you get children who are not sleepy until midnight or 1am, and naturally would sleep until 9am, 10am.”
The trouble is that we insist they run on the same timetable as adults. “Most schools still run on a 9am to 3:30pm basis,” says Wood, “despite the fact that wherever it's been piloted, later starting times are associated with better grades and less antisocial behaviour.” It would be a “no-brainer” to move school hours back, he says, but there are practical obstacles, such as parents needing to drop kids off at school before work: “It looks obvious, but trying to implement it can be really difficult.”
This leads to lots of young people being chronically sleep-deprived, a problem that is being exacerbated by phones and social media, says Stein. “We know that sleep is so important. Lack of it is linked to obesity and suicide and behavioural problems. And teenagers have this double whammy, because the area of the brain involved in executive function – which hasn’t developed fully in teenagers anyway – is particularly susceptible to sleep deprivation.”
“Adolescents tend to be physically extremely robust,” syas Wood. “Teenagers and young adults are the strongest that they'll ever be.
“They're the most robust to hunger, to poison, to tiredness, and all these sorts of things. The classic example of this is alcohol, where it takes a lot more alcohol to make an adolescent rat fall down than an adult rat. When I was younger I could have plenty of drinks and stay up all night; now I have half a bottle of wine and I just want to go to sleep.” However, the younger you are, the more long-term damage drinking seems to do, as well: “The neurotoxic effects are age-dependent, so the younger you are when you use alcohol the more likely it is to damage hippocampal nerve cells, for example.”
What’s more, they’re much less susceptible to disease. “There are childhood illnesses, very specific kinds of infections or injuries or cancers. And there are diseases of being old, cancers, cardiovascular disorders, neurological disorders. But young people are physically very fit. There aren't many physical illnesses of young people. By and large young people don’t get sick.”
A “very, very large proportion” of the health problems of young people is mental illness, says Wood. “By the age of 25, 75% of mental illnesses have already had their onset. It may even be younger than that. And why that should be is still not completely clear.”
It may be partly problems of development, or genes. But also, teenagers and young adults have to deal with a lot of major changes in their lives. “For example,” says Wood, “the change between primary and secondary school is hard. You go from being the biggest kid in school and knowing how everything works, to being the smallest kid and knowing nothing.” We don’t deal very well with changes like that at any point in our lives, he says – moving jobs or cities leaves adults vulnerable to mental health problems, too.
“Mental health research is the big thing at the moment, and it’s what makes this field so exciting,” says Stein. “It’s all about finding ways of preventing problems further down the line.
“Being a teenager is a stressful time, even for the most resilient of temperaments. But a lot of this stuff can be tempered, and I think resilience can be taught. A lot of the stuff we deal with is about helping individuals and their families cope with the emotional turmoil of teenage years.”
Wood’s own university, Birmingham, has a specialist youth mental health system, called Forward Thinking Birmingham. The mental health charity Mind also has a resource page for children and young people.
"I found being a teenager incredibly hard," says Stein. "I really felt at the mercy of my emotions. So I feel very sympathetic to teenagers – they're demonised as a group."
Wood says that adults often forget their own younger years. "People make comments like 'Adolescent brain development? Sounds unlikely!' It's as though, some time around age 25, some switch goes in our brains which wipes our memories.
"But the things you do as an adolescent aren't that different, or are only a matter of degree different, from the things we do as both children and adults. There's a danger in turning them into some alien species."
“Teenagers are unique,” says Stein. “They have a unique sensitivity. Their emotions, the way they feel about music – it's a really amazing time. If you came across a teacher at that age who really tapped in to your interests and your creativity, then it's a really fruitful time of self-discovery, your interests in the world around you.
“The teenage years are demonised, but it’s an opportunity for real growth, for emotional understanding, as long as you also understand that your thinking brain has not quite caught up with it.
“One thing that I often say to the teenagers is ‘Don't be scared of your emotions. Don't be scared of emotion, because if you harness them in the right way they can lead to wonderful things.'”