The Millon Clinical Multiaxial Inventory-III (MCMI-III) is a psychological assessment tool intended to provide information on psychopathology, including specific disorders outlined in the DSM-IV. It is intended for adults (18 and over) with at least an 8th grade reading level. The MCMI was developed and standardised specifically on clinical populations (i.e. patients in psychiatric hospitals or people with existing mental health problems), and the authors are very specific that it should not be used with the general population. However, there is a strong evidence base that shows that it still retains validity on non-clinical populations, and so psychologists will often administer the test to members of the general population.
The test is modeled on four scales
The test was normed on a sample of 998 male and female adults with a wide variety of clinical disorders.
Patients' raw scores are converted to Base Rate (BR) scores to allow comparison between the personality indices. The Base Rate scores are essentially where each score fits on a scale of 1-115, with 60 being the median score. Conversion to a Base Rate score is relatively complex, and there are certain corrections that are administered based on each patient's response style.
The Modifying indices are scored using a complex system in which the patient's responses in the other scales are compared and the raw and BR scores are taken from this. The Validity index is an exception to this. It consists of three questions, and so is scored between 0 and 3. It is not converted to a BR score.
The modifying indices consist of 4 scales - the Validity scale (V), the Disclosure Scale (X), the Desirability Scale (Y) and the Debasement Scale (Z).
They are used to determine a patient's response style, such as whether they were keen to present themselves in a positive light (indicated by an elevation on the Desirability scale) or exaggerate the negative aspects of themselves (indicated by the Debasement scale). It also is used to measure whether the patient was open in the assessment, or if they were unwilling to disclose details about themselves (the Disclosure Scale). These are compared against each other to gain an understanding of the patient's response style. For instance, elevated scores on the Disclosure and Desirability scales suggest a "cry for help" response style.
The Disclosure scale is the only scale in the MCMI-III in which the raw scores are interpreted and in which a particularly low score is clinically relevant. A raw score above 178 or below 34 is considered to not be an accurate representation of the patient's personality style as they either over- or under-disclosed.
The Validity Index consists of just three questions in which a response of "True" is extremely unlikely, such as "I was on the front cover of several magazines last year." While only consisting of 3 questions, the scale is very sensitive to random responding. A score of 2 or 3 on this scale would render the test invalid.
For the Personality and Clinical Syndrome scales, scores of 75-84 are taken to indicate personality trait, or (for the Clinical Syndromes scales) the presence of a clinical syndrome. Scores of 85 or above indicate the persistence of a personality trait or a clinical syndrome.