our sample, a proportion of heroin addicts report the abuse of cocaine. This makes our positive association with opioid addiction and the lack of association with cocaine addiction difficult to interpret. Considering that the OR in cocaine addiction was similar to that observed in the opioid addicted cohort, it is possible that with a larger sample size an effect of the SNP on cocaine addiction would have been detected. However, whether rs1076560 increases risk for drug dependence in general or has specific effects depending on the drug type remains to be elucidated.
