Brain abnormalities commonly seen in drug addicts are also found in the addicts’ sober siblings. The discovery, reported in the Feb. 3 Science,suggests that there are inherited but conquerable risk factors involved in drug dependency. What’s more, looking at how non-using siblings compensate for their inherited brain irregularities may eventually uncover clues to treating drug addiction.
“These brothers and sisters might show us strategies that we could teach to drug users,” says Karen Ersche of the University of Cambridge in England and lead author of the study.
It’s well known that people with drug addiction problems have irregular features in parts of the brain associated with self-control. Until now, it was unclear whether these abnormalities emerge after long-term drug abuse or if some people are born with brains that are more susceptible to drug addiction.
To answer that question, Ersche and her University of Cambridge colleagues analyzed brain scans of 50 people who are dependent on stimulants like cocaine, as well as scans from their non-using siblings and unrelated individuals of similar age and intelligence.
“This is an elegant design that allows them to say, ‘No, this was not something that relates to the drug exposure, this has something to do with heritability,’” says Nora Volkow, director of the National Institute on Drug Abuse in Bethesda, Md.
The brain scans revealed abnormalities among both the addicts and their siblings in the prefrontal cortex, an area of the brain that’s responsible for self-control. Also, the putamen, a structure involved in forming habits, tended to be larger in drug users and their siblings, while structures in the brain that manage responses to cravings tended to be smaller.
Drug users and their sibling groups were also found to have a weaker ability to exert self-control, based on behavior tests conducted as part of the study.