Measurement invariance of DSM-IV alcohol, marijuana and cocaine dependence between community-sampled and clinically overselected studies

Aims: To examine whether DSM-IV symptoms of substance dependence are psychometrically equivalent between existing community-sampled and clinically overselected studies. Participants: A total of 2476 adult twins born in Minnesota and 4121 unrelated adult participants from a case-control study of alcohol dependence. Measurements: Life-time DSM-IV alcohol, marijuana and cocaine dependence symptoms and ever use of each substance. Design: We fitted a hierarchical model to the data, in which ever use and dependence symptoms for each substance were indicators of alcohol, marijuana or cocaine dependence which were, in turn, indicators of a multi-substance dependence factor. We then tested the model for measurement invariance across participant groups, defined by study source and participant sex. Findings: The hierarchical model fitted well among males and females within each sample [comparative fit index (CFI)>0.96, Tucker-Lewis index (TLI)>0.95 and root mean square error of approximation (RMSEA)<0.04 for all], and a multi-group model demonstrated that model parameters were equivalent across sample- and sex-defined groups (ΔCFI=0.002 between constrained and unconstrained models). Differences between groups in symptom endorsement rates could be expressed solely as mean differences in the multi-substance dependence factor. Conclusions: Life-time substance dependence symptoms fitted a dimensional model well. Although clinically overselected participants endorsed more dependence symptoms, on average, than community-sampled participants, the pattern of symptom endorsement was similar across groups. From a measurement perspective, DSM-IV criteria are equally appropriate for describing substance dependence across different sampling methods.