variables (covariates) predicting a set of observed response variables (i.e., DSM-IV AUD symptom criteria). The MIMIC model includes three sets of relationships: those between the symptom criteria and the latent factors (the measurement model), those between the latent factors and the covariates (the structural regression equations), and those between the symptom criteria and the covariates (the direct effects). The presence of direct effects implies that there are differences in the measurement parameters of the factor model due to certain background characteristics (e.g., the factor models may differ for different subgroups in the population). Such effects indicate measurement non-invariance. The non-invariance of specific symptom criteria is an indication that individuals with a same level of latent trait respond differentially to the same measurement items if they belong to different subpopulation groups. For example, these groups may have different interpretations regarding the meaning of the symptom criteria or may have reasons not to respond truthfully to symptom criteria. Consequently, measurement non-invariance has the potential to distort the results of what is being measured. In this study, the MIMIC models involve only one latent factor representing the unidimensional trait of alcohol use disorder severity. Without covariates, MIMIC models are equivalent to IRT models,
