RENEE MONTAGNE, HOST:
Scientists in Britain have identified brain abnormalities that seem to make people more vulnerable to drug addiction. The abnormalities affect areas of the brain involved in self-control. As NPR's Jon Hamilton reports, these brain differences could help explain why addiction tends to run in families.
JON HAMILTON, BYLINE: Researchers have known for a long time that drug addicts' brains don't look like other brains. But they haven't been sure whether the differences are present from birth, or only develop after years of drug abuse. Karen Ersche, from the University of Cambridge in the U.K., led a team that tried to answer that question by studying the brains of 50 pairs of siblings. She says one sibling in each pair was an addict.
KAREN ERSCHE: Most of them were using cocaine or crack cocaine, but they were also using other drugs on top.
HAMILTON: The second sibling in each pair had no history of drug abuse. But Ersche says brain scans showed that all the siblings had brains that were unlike those of typical healthy people.
ERSCHE: The fibers that connect the different parts of the brain were less efficient in both, in the drug-dependent people - again, which is not surprising - but also in their brothers and sisters.
HAMILTON: These fibers connect areas involved in emotion with areas that tell us when to stop doing something. Ersche says when the fibers aren't working efficiently, it takes longer for a stop message to get through. And sure enough, another experiment showed that both siblings took longer than a typical person to respond to a signal telling them to stop performing a task. In other words, they had less self-control. Ersche says that's hardly surprising for the addicts.
ERSCHE: We know that in people who are addicted to drugs like cocaine, that self-control is completely impaired. These people use drugs and lose control on how much they use, when they use. They put everything at risk - even their lives, at risk.
HAMILTON: Ersche says the fact that non-addicted siblings also had impaired self-control offers strong evidence that these brain abnormalities are inherited. Ersche says the finding also raises a big question about the siblings who aren't addicts.
ERSCHE: How do they manage, with an abnormal brain, without taking drugs? How does their brain compensate?
HAMILTON: Ersche says she hopes another study can answer that question. In the meantime, Nora Volkow, director of the National Institute on Drug Abuse, says the findings about self-control have implications that go far beyond drug addiction.
NORA VOLKOW: Self-control, and the ability to regulate your emotions, really is an indispensable aspect of the function of the brain that enables us to succeed.
HAMILTON: Volkow says the part of the brain that decides whether to take a drug is also the part that helps us decide whether to speed through a yellow light, or drop out of school. And she says this brain circuit seems to be involved in a lot of common disorders.
VOLKOW: For example, probably one of the ones that attracts the most attention is attention hyperactivity disorder, or ADHD, where kids are unable to control their response to stimuli that distract them.
HAMILTON: Impulse control is also central to behaviors like compulsive gambling and compulsive eating. Volkow says the new study shows it's possible to identify people who have inherited a susceptibility to these sorts of problems. She says it also should help researchers figure out how to help susceptible people strengthen their self-control.
VOLKOW: Predetermination is not predestination. And it's understanding how these genetic effects are mediated that will allow us to prevent these trajectories into adverse diseases such as substance use disorders.
HAMILTON: The new research appears in the journal "Science."
Jon Hamilton, NPR News.