Teasing Out the Sibling Effect in Addiction


A new study from the Journal Science has taken a step forward in understanding sibling differences in addiction. The key question investigated was how the brains of siblings might differ if one is actively addicted and the other not.

The puzzle has been with us for some time. We know there is a genetic component to addiction – someone is more likely to be an addict if they have a family history of addiction. But how does this play out? Why does one family member become addicted and another stay sober?

To find out more, researchers imaged the brains of three sets of people: healthy people who weren’t addicted, siblings of addicts, and the addicts themselves. To narrow the field, the recruited only those addicted to cocaine.

What they found was that the sibling pairs showed a brain abnormality that separated them out from the healthy group. This seemed to show both shared the “addiction trait.” In the brother or sister that was actively addicted, they also found a further change in the brain – one known to occur with cocaine abuse. The picture is then of two people, siblings, both with the same genetic basis for addiction, but only one of the two managing to stay clean.

It appears that genetics primes someone to become an addict, but other causes lead to the disease. One possible culprit is exposure. Some people are resistant to the addictive properties of drugs, even a drug like cocaine. This group can “dip in” to use a substance when it is socially appropriate (like a weekend party) and let it go afterwards. But the addiction prone, once they get a taste aren’t usually strong enough to stop.

The study was conducted by Karen Ersche and others at the University of Cambridge. You can listen to a podcast interview where she discusses the research.


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