Stability of the Millon Clinical Multiaxial Inventory among psychiatric inpatients

This study investigated the stability of the Millon Clinical Multiaxial Inventory (MCMI) in a sample of psychiatric inpatients over a longer time period and from different perspectives than previous reliability studies. Test-retest reliability was assessed from three perspectives: correlation/regression, equivalence of dimensional structures across testings upon different admissions, and stability of personality style across testings. Some stability from a correlational perspective was found, with higher stability estimates indicated for the basic personality scales in comparison with the clinical symptom scales which is consistent with Millon's theory. The internal structure of the MCMI was essentially identical across testings. Although source of reinforcement and instrumental or coping style were stable across testings beyond chance, the MCMI profiles of a considerable number of subjects were inconsistent across testings. Correspondingly, clinicians should be cautious in using the MCMI to make categorical decisions regarding personality style with inpatients who are tested at admission and who have had repeated hospitalizations.