Personality disorder clusters and the Defence Style Questionnaire

Area of Science:

• Psychology
• Psychopathology
• Personality Disorders

Background:

• Personality disorders (PDs) are complex mental health conditions requiring accurate classification.
• Existing diagnostic systems, such as the DSM and Millon classifications, offer frameworks for understanding PDs.
• Defence mechanisms play a crucial role in psychological functioning and may differentiate between PD types.

Purpose of the Study:

• To investigate the discriminative power of 20 defence mechanisms in predicting personality disorder membership.
• To evaluate the utility of DSM-III-R and Millon's personality classification schemes.
• To compare the accuracy of the Coolidge Axis II Inventory (CATI) and Millon Clinical Multiaxial Inventory-II (MCMI-II) in classifying PD types.

Main Methods:

• Utilized the Defence Style Questionnaire (DSQ-40) to assess 20 defence mechanisms.
• Employed discriminant function analysis to determine the predictive contribution of defence mechanisms.
• Assessed personality disorders using the CATI and MCMI-II in a non-clinical sample.

Main Results:

• Discriminant function analysis supported the validity of both DSM and Millon classification systems.
• The CATI demonstrated high accuracy in classifying the DSM's odd cluster and Millon's ambivalent types.
• The MCMI-II accurately classified the DSM's odd and dramatic clusters, and Millon's independent and ambivalent types.

Conclusions:

• Defence mechanisms are valuable discriminators for personality disorder classification.
• Both the DSM and Millon systems show empirical support for their classification schemes.
• The CATI and MCMI-II exhibit differential accuracy in identifying specific personality disorder types.