MSNBC - Brain immaturity can be deadly: "Brain immaturity can be deadly
NIH study: Risk-taking diminishes at age 25
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 driving laws.
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 proven, 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.
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 construction."
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 happen later?"
'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 now."
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.
'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.'"