On the usefulness of measures of normal personality for clinical assessment: evidence of the incremental validity of the Revised NEO Personality Inventory.

As a means of examining the incremental validity of a normal personality measure in the prediction of selected Axis I and II diagnoses, 1,342 inpatient substance abusers completed the Revised NEO Personality Inventory (NEO-PI-R) and the Minnesota Multiphasic Personality Inventory--2 (MMPI-2) and were assessed with structured clinical interviews to determine diagnostic status. Results demonstrated that scores from the NEO-PI-R (a) were substantially related to the majority of diagnoses, accounting for between 8% and 26% of the variance in the diagnostic criteria; (b) explained an additional 3% to 8% of the variability beyond 28 selected MMPI-2 scale scores; (c) increased diagnostic classification an additional 7% to 23% beyond MMPI-2 scale scores; and (d) were significantly more useful when examined at the facet trait level than at the domain trait level. Implications for incorporating measures of normal personality into clinical assessment batteries are discussed.