Data on drug addiction co-morbidity was available for a subset of the individuals genotyped in this study. Amongst AA (N=336) and EA (N=336) cocaine dependents, 16.4% and 34.8% were also diagnosed as dependent on opioids respectively. In the opioid dependent populations, 68.4% of AA (N=225) and 34% of EA (N=394) also met criteria for cocaine dependence.
