Addiction is in part a "disorder of the brain," say scientists.
University of Cambridge scientists have found same abnormalities in the brains of addicts and their non-addicted brothers and sisters.
It has long been established that the brains of drug addicts have some differences to other people, but explaining that finding has been more difficult.
Experts were unsure whether drugs changed the wiring of the brain or if drug addicts' brains were wired differently in the first place.
The new study, published in the journal Science, attempted to answer that by comparing the brains of 50 cocaine or crack addicts with the brain of their brother or sister, who had always been clean.
Both the addicts and the non-addict siblings had the same abnormalities in the region of the brain, which controls behaviour, the fronto-striatal systems.
The finding has led researchers to suggest that these brains may be "hard-wired" for addiction in the first place, the BBC reported.
"These brothers and sisters who don't have addiction problems, what they can tell us is how they overcome these problems, how they manage self-control in their daily life," said lead researcher Dr Karen Ersche said.
It is possible that the similarities in the sibling's brains may not be down to genetics, but rather growing up in the same household. Research on the relationship between addiction and the structure of the brain is far from over.
However, many specialists believe these findings open up new avenues for treatment. Other experts said the non-addicted siblings offered hope of new ways of teaching addicts "self-control".
"If we could get a handle on what makes unaffected relatives of addicts so resilient we might be able to prevent a lot of addiction from taking hold," said Dr Paul Keedwell, a consultant psychiatrist at Cardiff University.
Prof Les Iversen, from the department of pharmacology at the University of Oxford, added: "These new findings reinforce the view that the propensity to addiction is dependent on inherited differences in brain circuitry, and offer the possibility of new ways of treating high-risk individuals to develop better 'self control." (ANI)