Different proportions of prescribed vs. illegal users of opioids in the Yale-Penn and the SAGE samples could have affected our results and may help to understand the different results from these samples. Neither the SSADDA (Yale-Penn) nor the SSAGA (SAGE) differentiates prescribed from illegal-recreational use of opioids, and therefore some subjects who endorsed DSM-IV OD criteria probably did so despite using opioids therapeutically. However, a majority (59.5%) of individuals in our samples who met criteria for OD endorsed at least five of the seven diagnostic criteria (mean criterion count = 6.6, Supplementary figure 1), suggesting that the GWS finding is attributable to moderate-to-severe OD, rather than being contributed to substantially by individuals who used opioids as prescribed, but required an increased dosage for pain control or who experienced withdrawal symptoms when opioid treatment was discontinued. The much greater proportion of participants in the Yale-Penn samples than SAGE who met the maximum number of (i.e., seven) OD criteria supports that interpretation. Also, compared to our (Yale-Penn) samples, the SAGE samples were recruited for alcoholism (42), cocaine dependence (43), or nicotine dependence
