Why teens are wired for risk

Hillary Tillotson, 19, and Tessa, 15, are sisters who have acted out as teens.

Story highlights

  • Teenagers' brains are still growing, rewiring
  • The prefrontal cortex doesn't finish developing until age 25, research has shown
  • Parents should emphasize rewarding good behavior, not punishment, professor says
It was hot at 3 a.m. in a small town in North Carolina, and there wasn't a lot for a group of teenagers to do. So, Hillary Tillotson, her brother and three other guys sneaked under a fence to go swimming at a private pool down the street. Only Tillotson and her then-boyfriend kept their clothes on, she said.
Two days later, a cop showed up at Tillotson's house. Some of the teens' accomplices had been bragging about their skinny-dipping adventure, and someone turned them in for trespassing. She and her brother had to go to court; their mother paid the fine.
"Sometimes I wonder where their brains are at," Tillotson's mother, Lori Lee, said of her children. "They do such impulsive things, and sometimes I just don't think they're thinking."
Neuroscientists confirm that teenagers do have brains, but they're wired differently from those of adults. Why many teenagers seek thrills, break rules and seem nonchalant about their own safety has been a question brain scientists have worked to answer in the last two decades. Top researchers use functional magnetic resonance imaging to see this brain activity.
A new study in the journal Nature found that structural changes in adolescents' brains correspond to fluctuations in IQ over time, with some young people improving and some falling back on these tests.
Teens improve at such tests at different rates, and it's difficult to know how someone will do a few years after the initial assessment, said study co-author Cathy Price at the Wellcome Trust Center for Neuroimaging. It's not yet clear whether fluctuations seen in this study are unique to this age group, or whether they would be similar across a lifespan.
Scientists typically refer to "the teenage brain" in 13- to 17-year-olds, but that doesn't mean that college students are totally "adults" yet. In fact, research from the National Institutes of Health has shown, the prefrontal cortex, a region of the brain associated with inhibition of risky behavior, doesn't get fully developed until age 25. The connections between the prefrontal cortex and other areas of the brain are also developing in teenagers. And a number of deep structures in the brain are influenced by changes in hormones, which may lead to heightened emotions.
The way that brain regions talk to one another in teenagers may explain teens' sometimes confounding behavior, scientists say. Even in their mid-teens, adolescents can make quick, efficient, correct decisions; in the heat of the moment, though, the brain's deep emotional centers will win out over reason.
"It's not like these brain parts aren't there. It's how they get wired and become fine-tuned with experiences," said BJ Casey, director of the Sackler Institute at Weill Medical College of Cornell University.
They get what they want
Teens are more sensitive than adults to rewards of situations or activities, and less sensitive to risks, brain imaging research shows.
Laurence Steinberg, a professor of psychology at Temple University and author of "You and Your Adolescent: The Essential Guide for Ages 10 to 25," has done research in this area. He found that when teenagers are in the presence of friends, the reward system gets aroused even more.
"It's not that adolescents don't understand risk. They understand it perfectly well," says Beatriz Luna, a neuroscientist at the University of Pittsburgh. "It's just that they find it more rewarding to impress their peers, and things of that sort, than the risk that's involved to their actual survival; it's just what they value at that point."
This would help explain why teens give in to peer pressure more easily than adults -- for instance, in breaking the law to jump into a pool in the middle of the night, as Tillotson did.
"I'm not someone who makes big mistakes like that. I'm usually the goody-goody in my family," says Tillotson, 19, of rural North Carolina.
Her 15-year-old sister, Tessa, is the family's rebel, their mother says. It's not unusual for Tessa to sneak out behind her mother's back and go to the park. "I don't like my mom to say no," Tessa says.
There's an evolutionary explanation for this kind of behavior: In most mammals, adolescence is the time when individuals leave the family environment, Steinberg said. Sensation-seeking leads pubescent creatures to go find sexual partners and a social structure outside the home. They need to become independent of their parents and adapt to new surroundings.
Venturing out into the wild and leaving the security of parents is a risky thing to do, so there must be some built-in biological mechanism to ignore the potential dangers of the wild, scientists reason.
"If it didn't happen, we wouldn't leave home and reproduce," Steinberg explains.
And what they want can be dangerous
The reward-seeking brains of teens may lead them to experiment with pleasure-inducing substances like drugs and alcohol, which are especially dangerous for this age group, scientists say.
Since vital structures in the teen brain are still developing, adolescents are more prone to brain damage from drugs and alcohol. Research has shown that teenagers who binge drink will have greater brain damage than adults. And teens are more vulnerable to stress, which may lead to an increased risk of depression later in life.
Marijuana can stay in a teenager's system for days, impacting the building blocks of learning and memory. That's because the teen brain probably has more receptors drugs to bind to -- the same is true for alcohol. And in teens who regularly use pot, IQ can permanently decrease, research has shown.
On the plus side, teens are rapid learners, since their brains are still developing.
But that also