Personality disorder clusters and the Defence Style Questionnaire.

This research examined the relative contribution of 20 defence mechanisms assessed by the 40-item Defence Style Questionnaire (DSQ-40) as discriminating variables in predicting membership in personality disorder (PD) clusters. The odd, dramatic and anxious clusters of DSM-III-R and the detached, dependent, independent and ambivalent groups of Millon were used as PD types. PDs were assessed by the Coolidge Axis II Inventory and the Millon Clinical Multiaxial Inventory-II in a non-clinical sample. Results of discriminant function analysis provide empirical support for the usefulness of both DSM and Millon classification schemes. The DSM's odd cluster and Millon's ambivalent types are classified most accurately with the CATI. The MCMI-II classifies most accurately the DSM's odd and dramatic, and Millon's independent and ambivalent, personality types.