Brain networks explain why some teenagers smoke

Washington - Scientists have been intrigued by why some teenagers start smoking or experimenting with drugs while others do not.

In the largest imaging study of its kind, involving the brains of 1,896 14-year-olds, scientists have discovered a number of previously "unknown networks" that go a long way towards an answer.

Robert Whelan and Hugh Garavan, psychiatrists at the University of Vermont, report that differences in these networks provide strong evidence that some teenagers are at higher risk for drug and alcohol experimentation -- simply because their brains work differently, making them more impulsive, the journal Nature Neuroscience reports.

This discovery helps answer a long-standing chicken-or-egg question about whether certain brain patterns come before drug use-or are caused by it, according to a Vermont statement.

"The differences in these networks seem to precede drug use," says Garavan, who also served as the principal investigator of the Irish component of a large European research project, called IMAGEN, that gathered the data about the teenagers in the new study.

In a key finding, diminished activity in a network involving the "orbitofrontal cortex" is tied with experimentation with alcohol, cigarettes and illegal drugs in early adolescence. "These networks are not working as well for some kids as for others," says Whelan, making them more impulsive.

Faced with a choice about smoking or drinking, the 14-year-old with a less functional impulse-regulating network will be more likely to say, "yeah, gimme, gimme, gimme!" says Garavan, "and this other kid is saying, 'no, I'm not going to do that'."

Testing for lower function in this and other brain networks could, perhaps, be used by researchers someday as "a risk factor or biomarker for potential drug use," Garavan says.