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|Monday, May 10, 2004 |

|What Makes Teens Tick |

|A flood of hormones, sure. But also a host of structural changes in the brain. Can those explain the behaviors that make adolescence so |

|exciting--and so exasperating? |

|By CLAUDIA WALLIS; KRISTINA DELL |

|Five young men in sneakers and jeans troop into a waiting room at the National Institutes of Health Clinical Center in Bethesda, Md., and |

|drape themselves all over the chairs in classic collapsed-teenager mode, trailing backpacks, a CD player and a laptop loaded with computer |

|games. It's midafternoon, and they are, of course, tired, but even so their presence adds a jangly, hormonal buzz to the bland, |

|institutional setting. Fair-haired twins Corey and Skyler Mann, 16, and their burlier big brothers Anthony and Brandon, 18, who are also |

|twins, plus eldest brother Christopher, 22, are here to have their heads examined. Literally. The five brothers from Orem, Utah, are the |

|latest recruits to a giant study that's been going on in this building since 1991. Its goal: to determine how the brain develops from |

|childhood into adolescence and on into early adulthood. |

|It is the project of Dr. Jay Giedd (pronounced Geed), chief of brain imaging in the child psychiatry branch at the National Institute of |

|Mental Health. Giedd, 43, has devoted the past 13 years to peering inside the heads of 1,800 kids and teenagers using high-powered...