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Are Some Teenagers Wired for Addiction?


In the largest imaging study of the adolescent brain ever conducted — involving 1,896 14-year-olds — scientists report in Nature Neuroscience that some teenagers may be more inclined to experiment with drugs and alcohol, simply because their brains work differently, making them more impulsive.

Moreover, different brain networks appear to be involved in the self-control problems of substance abuse among teenagers than those associated with attention deficit hyperactivity disorder, or ADHD, even though both problems stem, in part, from a failure to inhibit behavior, the scientists report.

“The behavior might look the same but there may be different brain regions contributing to that behavior,” says neuroimaging expert Dr. Robert Whelan at the University of Vermont, who was the study’s lead author. The study is part of a larger project funded by the European Union that is conducting a systematic neural, genetic and behavioral assessment of teenagers in Ireland, England, France, and Germany.

Whelan and his colleagues used functional magnetic resonance imaging, which tracks the changes in blood flow between neurons associated with mental activity. They monitored brain responses as the teenagers moved one hand in response to a stream of commands, a widely used research protocol called the “stop-signal task” that is much like a game of Simon Says.  Periodically — and unpredictably — the volunteers would be ordered to stop moving their hands. The researchers identified seven neural networks active when the teenagers could stop themselves and six other brain circuits active when they could not.

Generally, the researchers found that the adolescents with ADHD symptoms, which is the most common neurodevelopmental psychiatric disorder, and those who had used drugs or alcohol had an equally hard time handling the task.

Among those with a history of alcohol, cigarettes, and illegal drug use, however, they found that the impulse control problem was associated with diminished activity in a brain region called the orbitofrontal cortex. The researchers found an entirely separate set of impulse-control networks connected with the symptoms of ADHD, which were distinct from those associated with adolescent substance abuse.

“Our study lends credence to the idea that ADHD and substance abuse are not intrinsically linked together,” Whelan tells the Health Blog. “There appear to be different regions associated with different kinds of impulsivity.”

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