Multivariate discriminant function analysis of neurologic, pain, and psychiatric patients with the MMPI

The ability of the MMPI to classify five well-defined patient groups was investigated (N = 394; control, neurologic, psychiatric, chronic pain, and random). Clinical inspection and discriminant function analyses of basic clinical and research scales could not classify groups correctly, but discriminant function analyses of 37 variables loaded with CNS items (Cripe Neurologic Symptom items) correctly classified the groups with 78% overall accuracy (70% of neurologic, 62% of psychiatric, 81% of pain, 84% of controls, and 100% random). Results indicate that differential diagnosis is not possible with clinical inspection of scales, but complex statistical analysis of the MMPI is potentially useful in diagnosis and decision making. A method for applying the discriminant function analysis to individual cases is provided.