In light of the deficits in our understanding of the genetic factors contributing to OD and CD risk, we have sought to derive phenotypes that are under more direct genetic control that could facilitate understanding the disorders and identification of potential drug targets and risk pathways. Our group recently identified variants near OPRM1 associated with usual methadone dosage in a sample of individuals with OD [20]. Here, we report findings from a GWAS of two related phenotypes: the time between first reported use and first DSM-IV diagnosis of OD and CD. We analyzed each substance independently. Both cocaine and opioids are highly addictive [21]. Approximately 50% of individuals who ever use heroin develop OD [22], while about four percent of people who try cocaine become addicted within two years, with another 16% in a prodromal stage of addiction [23]. A few studies (one conducted in the primary cohort analyzed here) have examined risk factors associated with rapid progression to dependence. Conduct disorder and childhood physical abuse predicted rapid more development of OD and CD, while and alcohol and nicotine dependence diagnoses were associated with slower progression, and African Americans (AAs) progressed to OD more rapidly than European Americans (EAs) [24].
