Circular structure of the MCMI-III personality disorder scales

Millon's (1987) circular model of personality disorders was examined in a l arge sample of psychiatric patients (N = 2,366) who completed the Millon Cl inical 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 partiall ed out. Circular plots of the scales were examined against Millon's hypothe sized arrangement and the model was tested using confirmatory factor analys is. Results replicated those of Strack, Lorr, and Campbell (1990) with the MCMI-II. Millon's horizontal Impassive-Expressive dimension was recovered i n both regular and residual scores but the vertical axis appeared to repres ent an Impulsivity-Compulsivity dimension rather than the Autonomous-Enmesh ed continuum envisioned by Millon. Although scale order followed Millon's p redictions for the most part, a number of departures from theoretical expec tations were noted and none of the score sets yielded a good fit to the hyp othetical 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.