Psychosomatic Medicine, Vol 51, Issue 1 58-65, Copyright © 1989 by American Psychosomatic Society

ORIGINAL ARTICLES

A caution on the use of the MMPI K-correction in research on psychosomatic medicine

RR McCrae, PT Costa Jr, WG Dahlstrom, JC Barefoot, IC Siegler and RB Williams Jr
Gerontology Research Center, National Institute on Aging, Baltimore, MD 21224.

The MMPI K scale is widely used to screen for invalid responses and to adjust substantive scale scores for defensiveness. In a normal volunteer sample, correlations of MMPI clinical scales and the Cook-Medley Hostility (HO) scale with self-reports and peer ratings on the NEO Personality Inventory (NEO-PI) were decreased rather than increased by K-correction. Similarly, in a medical sample, structured interview-based ratings of Potential for Hostility were better predicted by uncorrected HO scores than by K-corrected HO scores. Finally, in a prospective study of mortality among lawyers, uncorrected HO scores were a significant predictor of all-cause mortality; K-corrected scores were not. The data suggest that, under some circumstances, the K scale may measure substantive traits rather than defensiveness, and should be used and interpreted with caution. Its use is probably contraindicated for most research on psychiatrically normal subjects.

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