The MMPI and MMPI-2 as predictors of psychiatric diagnosis in an outpatient sample

The MMPI and MMPI-2 were compared as predictors of psychiatric diagnosis in 100 male and 100 female outpatients who completed the test items in a single session. Test profiles and the clinical diagnosis were grouped into five categories (normal, neurotic, character disordered, psychotic, and other). The MMPI and MMPI-2 code types were in the same category in 75% of the cases. Both the MMPI and MMPI-2 had a 39% agreement rate with category of clinical diagnosis (p < .0001). Discriminant function analyses based on Scales L, F, K, 1, 2, 3, 4, 6, 7, 8, and 9 accounted for significant variance in diagnostic group, (p < .02), and two functions correctly classified 49% and 50% of the cases for the MMPI and MMPI-2, respectively. The rate of correct classification for normals was more than 70%. The rate of correct classification for psychotics was 55% for the MMPI and 30% for the MMPI-2. For both the MMPI and MMPI-2, it appears important not to rely on test findings alone as a basis for diagnostic decisions.