Scientists find a genetic cause for cocaine addiction
13 March 2006
Scientists have discovered that our genes have an impact on our reaction to cocaine and our likelihood of developing an addiction to the class A drug. The research is published this week in the online edition of PNAS, the journal of the American Academy of Sciences. It was carried out at the Medical Research Council (MRC) Social, Genetic and Developmental Research Centre at the Institute of Psychiatry, King’s College London.
Much of our desire to use/re-use drugs and the process of addiction depend on their impact on brain function. Cocaine’s action within the brain is relatively well understood. It strongly binds and inhibits the action of a protein called the Dopamine Transporter (DAT)1.
In this latest study, researchers examined the DNA of 700 cocaine abusers and 850 ordinary people and found that cocaine abusers had a specific genetic variation in DAT more frequently than the control subjects. People carrying two copies of this variant were 50% more likely to be cocaine dependent.
“This study is the first large scale search for a genetic variant influencing the risk of developing cocaine addiction or dependence. The target we investigated, DAT, is the single most important in the development of cocaine dependence. It makes sense that variation within the gene encoding DAT influences cocaine dependence,” said Dr. Gerome Breen, the lead investigator.
Analysis of this DAT variant revealed that an element of it was directly sensitive to cocaine. In the may brain it may act to reduce the level of DAT in response to the drug. This action could also make the brain more susceptible to cocaine’s addictive effects and might be important in influencing the initial stages of addiction.
“This research helps our understanding of the development of cocaine addiction. It could influence the design and use of drugs to treat cocaine abuse in the future. This means that although repeated exposure to cocaine will lead to compulsive use in everyone, it seems some people will become addicted to the drug more quickly than others because of a genetic difference,” said Camila Guindalini, who performed the genotyping analysis.
“I was asked to determine the functional effect of this risk variant. In our lab, we put the different versions into artificial systems that we use to test for functional effects and were surprised to find that the risk version appeared to alter its effect in response to cocaine,” said Prof. John Quinn of the University of Liverpool.
"This is a really exciting finding. It would be our hope that this is the first of many findings showing how genes as well as environment contribute to our risk for addiction. We think this may help predict drug response for our cocaine addiction patients but also how they might respond to different forms of psychological therapies," said Prof. Dr. Homero Vallada from the University of Sao Paulo Medical School, who collected the samples with Prof. Dr. Ronaldo Laranjeira, of the Federal University of Sao Paulo.
For further information, or to request an interview with Dr Gerome Breen or Camila Guindalini please contact the MRC press office on 020 7670 6139.
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