Drug use linked with brain differences in teens

Teens who have used drugs even just once in their lives have brain characteristics that are different from those who have never used drugs, a new study finds.

In the study, the researchers scanned the brains of 71 Mexican-American 16-year-olds, and asked the teens whether they had ever used drugs, including cigarettes, alcohol, marijuana and other drugs. The researchers looked at whether the brain activity of certain regions was in sync (a measure known as "functional connectivity"), which suggests that the regions are talking to one another.

Among teens who'd ever used drugs, a brain region known as the nucleus accumbens which is thought to play a role in the rewarding feeling that can come with taking drugs was more in sync with areas of the brain in the prefrontal cortex, compared to in teens who'd never used drugs. The prefrontal cortex is involved in decision making, planning and other behaviors that require complex thinking.

But the nucleus accumbens was less in sync with an area near the hippocampus, which is important for memory formation, in teens who had used drugs, compared with those who had never used. [10 Facts Every Parent Should Know about Their Teen's Brain]

Because the study was conducted at just one point in time, the researchers cannot determine the reason for these brain differences, said study researcher David G. Weissman, a graduate student at the University of California, Davis Center for Mind and Brain. It could be that drug exposure is responsible for the differences. But Weissman said he suspects that these brain differences existed before drug use, and underlie a tendency to take risks, which includes using drugs, he said.

Weissman said the level of drug use among the teens in the study was typical of teens that age about half had used drugs before, and they did not use drugs very frequently.

"It's possible, but seems unlikely, that that level of use would produce significant changes [in the brain], but it's an open question," Weissman said.

The researchers plan to continue to scan the brains of these teens over time, and see if there are any changes in the results, including whether there are changes in teens who start using drugs.

The new finding "brings up an intriguing idea that there are differences that we can observe in the brain in the way that it's connected that relate to whether or not kids are using substances," said Weissman, who conducted the study with Amanda Guyer, an associate professor at UC Davis, and colleagues.

Future studies could help researchers gain a better understanding of what leads teens to use substances or participate in other risky activities, Weissman said. Such studies may help researchers understand who is at risk for developing later life problems because of early drug use, Weissman said.

The study was funded by the William T. Grant Foundation, an organization that funds research on youth.It was presented last month at the meeting of the Association for Psychological Science in San Francisco, and has not yet been published in a peer-reviewed journal.

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