The Millon Clinical Multiaxial Inventory II: Stability over Time? A Seven-year Follow-up Study of Substance Abusers in Treatment

Measuring personality disorders among substance abusers may entail special problems related to the reliability and validity of the instruments. The Millon Clinical Multiaxial Inventory II (MCMI-II), a well-known self-reporting instrument, was used in a prospective study of drug abusers from 21 treatment programs in Norway (n = 481) to investigate the influence of substance abuse on the reliability and stability of the MCMI personality traits at intake to treatment and after 7 years (n = 342). As regards the drug-abusing and drug-free subgroups, the MCMI-II dimensional scores were equally reliable and stable in both groups, and were not influenced by the abusing state. Using the MCMI-II in a categorical diagnostic way did not show sufficient predictive validity. The MCMI-II dimensional scores should therefore be used to measure personality disorder traits among help-seeking and former drug abusers.