Drug addicts and their non-addicted siblings share certain features in the brain, suggesting a susceptibility to addiction is inherited, but is also a flaw that can be overcome.
Researchers who scanned the brains of 50 pairs of brothers and sisters, of whom one sibling was a cocaine addict, found that both had brain abnormalities that made it more difficult for them to exercise self-control.
The findings increase the understanding of why some people with a family history of drug abuse have a higher risk of addiction and could point to new treatments to help people learn how to take control before addictions set in.
The World Health Organisation estimates at least 15.3 million people worldwide have drug-use disorders.
A study in the Lancet medical journal in January said as many as 200 million people used illicit drugs worldwide each year.
Scientists had noticed brain differences in drug addicts before, but were not sure whether those differences came before the drug use, or were as a result of it.
Researcher Karen Ersche said the next step would be to explore how the siblings who didn't take drugs managed to overcome their brain abnormality.
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