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February 05, 2012

Inherited Vulnerability to Drug Addiction Discovered

by Jessica Berman

Brain abnormalities found in addicts and their non-addicted siblings

Scientists have discovered structural abnormalities in the brains of drug addicts and their non-addicted siblings, a finding that suggests there may be an inherited vulnerability to addiction, and that behavioral therapies could help addicts recover.  

Substance abuse is known to run in families, according to experts, who say that having an addicted family member increases a person’s risk of addiction by eight to ten percent above the general population.  

Researchers have yet to identify an addiction gene. But Karen Esche at the University of Cambridge in Britain says the brain abnormalities found in addicts and their non-addicted siblings suggest these congenital differences might be to blame for the increased vulnerability to drug abuse.  

“This may suggest that some of the impairments that we see in the drug users are not caused by the drugs or [do not] predispose them to addiction,” Esche says.

Esche's team used magnetic resonance imaging to take pictures of the brains of cocaine addicts and their non-addicted siblings. The images showed the same patterns of abnormalities in the pre-frontal and striatal regions of the brain, patterns not evident in the brains of unrelated volunteers.

Researchers also tested the study participants to see how quickly they could switch from one task to another. The addicted sibling pairs fared much worse than the volunteers, suggesting high levels of impulsivity and a lack of self-control.

“Which again puts them at risk of taking drugs, because what we see in addiction is that that self-control gets lost," Esche says. "Loss of control - loss of control over drug use - is a hallmark of addiction.”

Nora Volkow, director of the U.S. National Institute on Drug Abuse, says the study suggests the brain abnormalities observed in the addicted sibling are not due to chronic and repeated drug abuse. She believes people with a biological vulnerability to drug abuse can resist the temptation, which is good news for drug addicts.

“Even if you have a vulnerability in your brain that makes those areas not function properly, you can overcome it by interventions that can help you strengthen it,” she says.

According to Volkow, aerobic exercise has been shown to improve impulse control. So, too, have computer training programs designed to strengthen the pre-frontal areas of the brain that have been implicated in addiction.