The chances of becoming addicted to cocaine could depend on genes, the Institute of Psychiatry has found.
It identified a gene variation where cocaine would more markedly inhibit a protein that controls removal of key mood chemical dopamine in the brain.
Two copies of the variant made people 50% more likely to be cocaine abusers.
DNA of 700 cocaine abusers and 850 other people were compared for the study published online by Proceedings of the National Academy of Sciences.
This study is the first large scale search for a genetic variant influencing the risk of developing cocaine addiction
Dr Gerome Breen
Cocaine's action within the brain is relatively well understood.
Its key effect is that it strongly inhibits the action of a protein - DAT - which controls removal of excess dopamine from the junctions between nerve cells in the brain.
This leads to nerve cells effectively being overloaded with dopamine, which is thought to contribute to the 'high' associated with taking cocaine.
The latest study identified a specific variation in the genetic code controlling production of the DAT protein.
People carrying two copies of this particular variant were 50% more likely to be cocaine dependent."