This study leveraged the individual genotypic and phenotypic data available from the cohorts participating in the PGC-SUD workgroup. There is growing support for the idea that the genetic architecture of substance exposure is different from that of substance dependence13, 14. Based on these previous findings, we hypothesized that OD and OE are biologically different and therefore focused the present opioid study on three association tests: i) difference between opioid dependent (DSM-IV) and opioid exposed; ii) difference between opioid dependent and opioid unexposed, and iii) difference between opioid exposed and opioid unexposed. The results of these analyses provided information regarding the genetic differences between OD and OE.
