A NOTE ON THE EXTENSION OF MMPI CONFIGURAL RULES THEODORE F. HENRICHS

Unirretsity of Miaaouri S h l of Medicine

INTRODUCTION In a recent paper“) a set of configural rules was presented for discriminating

among MMPI profiles of male psychiatric patients grouped into broad diagnostic categories. These rules were based on ones derived by Meehl and Dahlstrom(*) for discriminating psychotic from neurotic MMPI profiles, and attempted to extend the applicability of this program to include the discrimination of MMPI profiles characteristic of character and behavior disorders. Routine application of these rules to appropriate MMPI profiles results in ultimate classification into one of four categories : P-type (psychotic), N-type (neurotic) , PD-type (character and behavior disorders) , or I (indeterminate).

RULE DERIVATION The present study presents data derived from the application of this system of

rules, with slight modifications, to samples of female psychiatric patients. These samples have highly similar parameters to the previously employed male samples. The derivation sample consisted of the MMPI profiles of female psychiatric in- patients (N = 73) and outpatients (N = 27) from the University of Missouri Medi- cal Center. All profiles fulfilled the necessary validity screening criteria. The age range of the sample was 18 to 60 and, as far as could be determined by the records, none were diagnosed as mentally deficient, as having central nervous system dysfunction, or receiving a course of ECT. A psychological report was available on all cases which allowed for clear disposition, prior to the application of the configural rules, into one of three categories: N, P, or PD. Forty persons in this sample were described as neurotic, 28 were called psychotic, and 32 were disorders of character.

In transposing the earlier rules developed on male samples, attention was initially focussed on the computation of differences between scale pairings called Beta [(PT + Sc) - (Hs + D)] and Delta [(PD + PA) - (Hs + HY)] scores by Meehl and Dahlstrom. ( 3 ) The T-score differences between males and females for any given raw scale score on the clinical scales suggested that an increase in the delta cutting scores used in various rules might be appropriate for the female samples. This adaptation and slight rule modifications for profiles falling under two other rules in the total sequence resulted in the classifications shown in Table 1 for the de- rivation sample. H (“hit”) and M (“miss”) are employed in the sense of concurrent validity. The H ratio is termed “hit-rate”.

P.

H + M

TABLE 1. RESULTS IN DERIVATION AND CROSS-VALIDATTON SAMPLES

H

N 7% H% M% 1% H + M P*

Results of Modified Rule Application on Derivation Sample Neurotic 40 40 65.0 12.5 22.5 83.9 <.001 Psychotic 28 28 67.9 10.7 21.4 86.3 <.001 Character Disorders 32 32 53.1 25.0 21.9 68.0 <.001 Total 100 - 62.0 16.0 22.0 79.5 <.001

Results in Cross Validation Sample Neurotic 40 41.7 67.5 20.0 12.5 77.1 <.001

Total 96 62.5 22.9 14.6 73.2 <.001

Psychotic 26 27.1 69.2 15.4 15.4 81.8 <.001 Character Disorders 30 31.2 50.0 33.3 16.7 60.0 <.005 -

*chi-square test.

52 THEODORE F. HENRICHS

CROSS VALIDATION These ruled were cross-validated on the MMPI profiles of another sample

(N = 96) which met all the criteria of the derivation sample; however, principally to increase sample size, 25 inpatients from Fulton State Hospital, Fulton, Missouri and 17 inpatients from Mendota State Hospital, Madison, Wisconsin were included. 24% of the total sample were outpatients. The results of the rule application to this sample also appear in Table 1.

The “hit rates” for the subgroups and for the total cross validation sample compare favorably with results obtained previously on male psychiatric patients. These were 91.7, 70.0, 57.1, and 72.2 respectively for N-type, P-type, PD-type and the total cross-validation sample. The PD-type “hit rate” continues to remain the lowest for the subgroups as a result, primarily, of a lack of success in effectively dis- criminating between PD-types and P-types. In the earlier male sample 92% of the PD-type “misses” in the cross validation sample were called P-type by the rules, in the present cross-validation sample the figure is 80%.

There are data from other similar populations which bear on this problem. Marks and Seeman (2), for example, list broad diagnostic classifications similar to the ones used in the present study for MMPI profiles clustered according to certain rules. Their rules, in general, apply to psychiatric inpatients and outpatients of both sexes. If one considers the total group of “misses” in the male and female derivation and cross-validation samples employed for the development of the present system of rules where the diagnostic statements indicated the presence of a character or behavior disorder and the rules classified the MMPI profile as P-type, 12 of the total 27 “misses” can be classified by one or another of Marks and Seeman’s rules. The mean psychiatric diagnostic breakdown for this group of 12 would be 44% P, 22% PD, 16% N - the residual would be classified as brain syndrome. Thus, difficulty in discriminating effectively between P-type and PD type MMPI profiles of psychiatric patients would seem to be a trend whether one initially clusters groups according to profile configurations or broad diagnostic categories. While the present system of rules discriminates at a level significantly better than chance, improvement is still needed from a clinical point of view.

SUMMARY A set of objective configural rules for discriminating among the MMPI profiles

of male psychiatric patients grouped according to broad diagnostic classifications were applied, with slight modifications, to a sample (N = 100) of female psychiatric patients. The modifications primarily involved the selection of appropriate cutting scores used in various rules in the total sequence. These rules were then cross-vali- dated on another sample (N = 96). Apparent “test misses” involving the discrim- ination of MMPI profiles characteristic of character and behavior disorders were discussed. The data indicated that, while the present system of rules discriminates at a statistically significant level, improvement is still needed before routine clinical use would be acceptable.

REFERENCES 1. HENRICHS, T. F. Objective configural rules for discriminating MMPI profiles in a psychiatric

2. MARKS, P. A. and SEEMAN, W. Actuarial Description 01 Abnormal Personal i ty . Baltimore:

3. MEEHL, P. E. and DAHLSTROM, W. G. Objective configural rules for discriminating psychotic

population. J . c l in . Psychol. , 1964,20, 157-159.

Williams & Wilkins, 1963.

from neurotic MMPI profiles. J . consult. p s y c h l . , 1960,24,375-387.

‘A mimeographed copy of these rules is available from the author on request.