These results are based on treatment-seeking, opioid-dependent adults, and the sample is not necessarily representative of all adults with a SUD. Treatment-seeking individuals may have different characteristics than persons who are being screened in primary care settings but who do not present seeking care for SUDs. While our results are consistent across substance classes, replication among substance users in different settings, including non-opioid dependent individuals, is needed. Another limitation is reliance on participants’ self-reports, which are subject to reporting bias; however, biomarkers are not available for SUD screening and diagnosis. Because assessments of SUDs rely on self-reports, IRT analysis can provide independent, psychometric evaluation for self-reported measures (Wu et al., 2009a; Wu et al., 2010). Lastly, the small sample size of hallucinogen (n=58) or inhalant (n=11) users precluded detailed analysis and interpretation of results.
