Risk-taking All in Their Heads?
NIH study: Part of brain that inhibits risky behavior isnít
fully formed until age 25.
by Elizabeth Williamson, Washington Post, February 1,
For more articles like this
By most physical
measures, teenagers should be the world's best drivers. Their
muscles are supple, their reflexes quick, their senses at a
lifetime peak. Yet car crashes kill more of them than any other
cause -- a problem, some researchers believe, that is rooted in
the adolescent brain. A National Institutes of Health study
suggests that the region of the brain that inhibits risky
behavior is not fully formed until age 25, a finding with
implications for a host of policies, including the nation's
"We'd thought the highest levels of physical and brain maturity
were reached by age 18, maybe earlier -- so this threw us," said
Jay Giedd, a pediatric psychiatrist leading the study, which
released its first results in April. That makes adolescence "a
dangerous time, when it should be the best."
Last month, Sen. William C. Mims (R-Loudoun) cited brain
development research in proposing a Virginia bill that would ban
cell phone use in vehicles by drivers younger than 18. It passed
In Maryland, Dels. Adrienne A. Mandel and William A. Bronrott
said the research could bolster three bills the Montgomery
County Democrats submitted to the legislature Friday. The bills
would expand training and restrict passenger numbers and cell
phone use for certain teenage drivers.
The measures also are supported by crash statistics and a
soon-to-be-released study from Temple University, which used a
driving-style test to show that young people consistently take
greater risks when their friends are watching.
"This goes toward supporting evidence that the judgment of teens
further deteriorates with distractions. These crashes are
preventable," Mandel said. "I would welcome [researchers']
testimony at our bill hearings."
The research has implications beyond driving: Attorneys cited
brain development studies as the U.S. Supreme Court considered
whether juvenile offenders should be eligible for the death
penalty. The court is expected to reach a decision by midyear.
Critics of brain-imaging research -- and Giedd himself --
emphasize that there is no proven correlation between brain
changes and behavior. Giedd, however, said the duration and
depth of the study mean "it's time to bring neuroscience to the
table" in the teen driving debate.
"We can determine what is the relationship between brain
development and driving ability and what we can do to make it
better," Giedd said.
At Temple University in Philadelphia, psychology professor and
researcher Laurence Steinberg plans a new study: scanning
teenagers' brains while they perform a task that simulates
driving decisions, in an effort to understand the biological
underpinnings of risk-taking among young people.
Giedd intends to pursue similar studies with his subjects,
focusing on ways to give young people, and those responsible for
them, more tools for beating the odds.
Teenagers are four times as likely as older drivers to be
involved in a crash and three times as likely to die in one,
according to the Insurance Institute for Highway Safety.
"Right now our first subjects are reaching driving age," Giedd
said. "What better application could there be than saving their
Lily and Zoe Ulrich, 15-year-old identical twins from Frederick,
have been part of Giedd's study at NIH for two years. When they
signed up, they answered questions about their diet, athletics,
social habits, peer pressure, language skills and intellectual
The blond, 5-foot-4 sisters wear glasses, earn straight A's and
often finish each other's sentences. They will receive their
learner's permits this month. "I'm excited . . . it's really
cool," Lily said. "I'm a little more nervous," said Zoe. "We
think the same a lot of the time but not always."
Giedd would like to know why.
Sitting in his closet-size office in NIH's sprawling Building
10, he turns to his laptop, where the fruit of 13 years' work
appears. It's an eight-second, time-lapse image of the brain,
swept by a vivid blue wave symbolizing maturing gray matter. The
color engulfs the frontal lobes and ends in "a direct hit,"
Giedd said, with the dorsal-lateral prefrontal cortex, just
behind the brow.
About as thick and wide as a silver dollar, this region
distinguishes humans from other animals. From it, scientists
believe, come judgments and values, long-term goals, the
weighing of risks and consequences -- what parents call wisdom
or common sense and what science calls "executive functions."
While society and tradition have placed the point of
intellectual maturity, the "age of reason," years earlier, the
study -- an international effort led by NIH's Institute of
Mental Health and UCLA's Laboratory of Neuro Imaging -- shows it
comes at about age 25.
The process is generally completed a year or two earlier in
women but varies greatly from person to person. Why that is,
Giedd said, "we still don't know."
"We have to find out what matters. Diet? Education, video games?
Medicine, parenting, music? Is the biggest factor whether you're
a musician or a jock or the amount of sleep you get?"
As important, Giedd said, is the study's finding that the brain
matures in a series of fits and starts. While it remains to be
proved, he said, this "may be a key to when the brain is most
receptive" to learning certain skills, such as driving.
The study, which is ongoing, involves scanning the brains of
2,000 people ages 4 through 26 using magnetic resonance imaging,
a radiation-free tool that permits researchers to view the
organs of healthy people in minute detail.
Every two years, study participants come to the Bethesda-based
National Institute of Mental Health, where they are scanned and
interviewed. Half the children are healthy, and half have
brain-related disorders. In the next phase, researchers plan to
focus almost solely on twins, hoping to expand beyond the 180
pairs participating now, to measure the impact of environmental
factors on the maturing brain.
Giedd said he's been bashed by teenagers who said the study
suggests they're brain-damaged. On the contrary, he said:
"Teenagers' brains are not broken; they're just still under
The pattern probably serves an evolutionary purpose, he said,
perhaps preparing youths to leave their families and fend for
themselves, without wasting energy worrying about it.
The findings imply that many life choices -- college and career,
marriage and military service -- often are made before the
brain's decision-making center comes fully online. But for young
adults, "dying on a highway is the biggest risk out there,"
Giedd said. "What if we could predict earlier in life what could
A 'Period of Recklessness'
Temple's Steinberg said the NIH/UCLA research supports his
theory that teen recklessness is partly the result of a critical
gap in time -- starting with the thrill-seeking that comes in
puberty and ending when the brain learns to temper such
behavior. Since children today reach puberty earlier than
previously, about age 13, and the brain's reasoning center
doesn't reach maturity until the mid-twenties, Steinberg said,
"this period of recklessness has never been as long as it is
In a study to be published this year, Temple researcher Margo
Gardner and Steinberg illustrated the impact of peer pressure on
risk-taking. Volunteers in three age groups -- 13 to 16, 18 to
22 and 24 and older -- were told to bring two friends to the
study, which involved an arcade-style driving game.
To "win," participants guided a car through a course as quickly
as possible. Periodically, a yellow warning light flashed, and
some time later a "wall" popped up. If players hit it, they lost
all their "points."
Participants took the test alone and with their friends in the
room. Researchers found that those in the two younger groups
consistently took more chances with friends present. Those 24
and older behaved equally cautiously, regardless of whether
friends were watching.
The results help show why teenagers are more likely to drink,
take drugs or commit crimes in groups, he said. They're also
reflected in auto crash statistics.
According to the Arlington-based Insurance Institute for Highway
Safety, the chances of a crash by a 16- or 17-year-old driver
are doubled with two peers in the vehicle and quadrupled with
three or more. "Every passenger you add increases the risk,"
said Alan Williams, chief scientist at the institute. The brain
and behavior studies, he said, "certainly tie in with what we
After a spate of teen driving deaths across the Washington
region in the fall, Maryland is attempting to join Virginia and
the District in limiting the number of unrelated passengers in
cars with young drivers. In addition to cell phone restrictions
that the Maryland and Virginia legislatures are considering,
Maryland Gov. Robert L. Ehrlich Jr. (R) is backing a measure
that would revoke the licenses of convicted drunk drivers under
age 21, for as long as five years.
Steinberg said he agrees with such approaches. "We have to limit
the harm adolescents [encounter], rather than to try and change
The best way to do that, he added, "is by passing laws."
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