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Brains of siblings with a family history of drug addiction show similar abnormalties.

Siblings of drug abusers share equal risk for addiction

by Mitch Montoya
Feb 02, 2012

In families with a history of drug abuse, siblings who did not use drugs demonstrated similar brain patterns and poor self-control as their drug-addicted brothers and sisters, British researchers reported Thursday in the journal Science.

Siblings with a family history of substance use grew up in abusive homes, but only some became addicts, neuroscientist Karen Ersche and her colleagues from Cambridge University said.

“People are eight times more likely to become addicted to drugs if they have a family history,” she said. “We wanted to know how people managed to come from troubled backgrounds and not develop addictions like their brothers and sisters.”

Researchers tested brain scans in 50 sibling pairs and discovered definite abnormalities compared with the individuals without a family history, the study showed.  The drug addicts and their siblings exhibited lower volumes of gray matter in parts of the brain associated with compulsive behavior.

Participants also performed self-control tests to measure their tendency for addiction. Siblings in the study underwent a stop-signal test that required them suppress a response when they heard a sound.  

While researchers expected the addicts to have a low level of self-control, they were surprised to find that the siblings also had lower self-restraint, Ersche said.

“If you struggle to control behavior then there is a risk that the drugs will take over,” she said.

The results of the study have significant implications for further treatment and understanding underlying causes of addiction, researchers said.

Interventions that focus on improved self-control is one avenue researchers are exploring, Ersche said. Using information about why siblings didn’t succumb to compulsive or addictive behavior is another important key in battling addiction.

Finding a familial risk for addiction does not necessarily mean that people will become addicts, said Joseph Troiani, director of the substance abuse program at the Adler School of Professional Psychology in Chicago.

“Both siblings may have a predisposition for a risk of drug abuse,” he said. “It really depends on the exposure factor which could be drinking because of stress or other social situations.”

Understanding why certain family members abstained from drugs while others didn’t is a complicated problem, Troiani explained. It could be as simple as they didn’t enjoy the experience of drinking or using drugs. It could also be something more complicated like they realized they had a problem early on.

“There are a lot of early intervention techniques,” he said “If someone receives a DUI or other offense they are required to be evaluated for a substance abuse problem.”

A critical next step for substance abuse researchers is understanding what causes a person to spiral out of control, Ersche said. If they are able to identify high-risk people and utilize early intervention that reinforces self-control, addiction could stop attacking a family tree.