Circular structure of the MCMI-III personality disorder scales

Millon's (1987) circular model of personality disorders was examined in a large sample of psychiatric patients (N = 2,366) who completed the Millon Clinical Multiaxial Inventory-III (MCMI-III; Millon, 1997) as part of routine assessment after presentation for treatment. Principal components analyses were conducted to identify the first two dimensions in MCMI-III base rate scores, weighted and unweighted raw scores, and nonoverlapping scale scores. Similar analyses were made on these scores when acquiescence was partialled out. Circular plots of the scales were examined against Millon's hypothesized arrangement and the model was tested using confirmatory factor analysis. Results replicated those of Strack, Lorr, and Campbell (1990) with the MCMI-II. Millon's horizontal Impassive-Expressive dimension was recovered in both regular and residual scores but the vertical axis appeared to represent an Impulsivity-Compulsivity dimension rather than the Autonomous-Enmeshed continuum envisioned by Millon. Although scale order followed Millon's predictions for the most part, a number of departures from theoretical expectations were noted and none of the score sets yielded a good fit to the hypothetical structure. Millon's model appears to have promise as a circumplex that can encompass all of the personality disorders but changes are needed to rectify discrepancies between the theory and empirical findings.