An international team of researchers has discovered regions of the brain that might help scientists understand why some teenagers abuse drugs and others are able to resist the temptation.
Researchers say the brain differences make some young people more impulsive, which is a risk factor for substance abuse.
In the largest-ever imaging study of the human brain, researchers used magnetic resonance imaging machines to examine the brains of nearly 2,000 14 year olds from across Europe. During the imaging, the teenagers engaged in an impulsivity task that measured their reaction time to certain stimuli. The brain regions that lit up were in an area that has been associated with impulsivity.
Diminished neural activity in these areas was seen in the adolescents who had experimented with illegal drugs, alcohol and cigarettes. Researchers say that might be a marker for substance abuse.
Robert Whelan, a researcher in the department of psychiatry at the University of Vermont, oversaw the Irish component of the study. He says investigators found that about half of the teenagers examined showed underactivity in the newly discovered brain regions.
"It's actually surprisingly high, yes," he says. "You wouldn't think that 14 year olds could actually engage in these types of behaviors. And we had quite a number of participants that used harder drugs as well, mostly marijuana. But you have to remember they are only 14 years of age."
Whelan says the neural differences were also found in teens diagnosed with attention deficit hyperactivity disorder, or ADHD - a condition marked by difficulty paying attention, concentrating and staying on task. But diminished activity in adolescents with ADHD involved different neural networks that Whelan says does not put teens at increased risk for substance abuse.
Whelan says there could many reasons why adolescents abuse alcohol and drugs, including genetics and peer pressure. So at this point, Whelan says, assessing a teenager's potential risk of substance abuse using magnetic resonance imaging is impractical and very expensive.
"All we've really done is...uncovered one piece of the puzzle. It's probably an important piece in the sense that it's desirable to know what's happening in the brain. But I think there are so many factors for drug use that any test like this is a long, long way off."
