Discriminant Validity of the MMPI-Borderline Personality Disorder Scale

Psychological Assessment: Copyright 1991 by the American Psychological Association, Inc. A Journal of Consulting and Clinical Psychology 1040-3590/91/$3.00 1991. Vol. 3, No. 2. 232-238 Discriminant Validity of the MMPI-Borderline Personality Disorder Scale Timothy J. Trull University of Missouri-Columbia The discriminant validity of the Minnesota Multiphasic Personality Inventory (MMPI) Borderline Personality Disorder scale (MMPI-BPD) was investigated in a sample of psychiatric inpatients by comparing the MMPI-BPD scores of a criterion group of patients who received a discharge diagnosis of borderline personality disorder (BPD) with the scores of several other DSM-111-R diagnostic groups that did not overlap with the BPD group. Results indicated that the MMPI-BPD scale scores discriminated the BPD group from an "other personality disorders" comparison group and from a schizophrenia-schizoaffective group. MMPI-BPD scores of 2 mood-disorder comparison groups, however, were not significantly different from those of the BPD criterion group. The discriminative ability of the MMPI-BPD scale was compared with that of individual MMPI clinical scales as well as several MMPI codetypes. Implications for the development of scales to optimize the differential diagnosis of BPD are discussed. Borderline personality disorder (BPD) is the most frequent personality disorder diagnosis made in both outpatient and inpatient settings (Widiger & Trull, in press). As such, there is a great need for a self-report instrument that is a reliable and valid indicator of BPD to aid in assessment. Although a number of studies have compared Minnesota Multiphasic Personality Inventory (MMPI; Hathaway & McKinley, 1983) clinical scale scores of patients diagnosed with BPD with scores of other psychiatric patients, there is at present no consensus as to an MMPI codetype specific to BPD (Gartner, Hurt, & Gartner, 1989; Morey & Smith, 1988; Widiger, Sanderson, & Warner, 1986). For example, Morey and Smith (1988) reviewed 12 studies that reported MMPI scale scores for BPD subjects and concluded that the only two consistent findings were (a) an elevated F scale, and (b) a high degree of overall profile elevation. Although elevations on Scales 2, 4, 6, 7, and 8 occur frequently in BPD samples, research suggests that these scales are sensitive to, but not specific to, the BPD diagnosis. Perhaps this is not too surprising because the original MMPI scales were developed in the context of an older psychiatric classification system that does not correspond well with contemporary psychiatric nomenclature. In sum, the search for a specific BPD-MMPI codetype has not, to date, been fruitful. It is conceivable, however, that responses to MMPI items can reliably discriminate BPD patients (or patients diagnosed with any of the other personality disorders) from other diagnostic groups. With this in mind, MMPI scales to assess the 11 personality disorders identified in the Diagnostic and Statistical Man- Portions of this article were presented at the Annual Meeting of the American Psychological Association in Boston, Massachusetts, August, 1990. I thank Thomas A. Widiger, Meg A. Klein, Cynthia Sanderson, Patricia Frazier, Eric Martin, and Kim Breaux for their help at various stages of this project. In addition, I acknowledge the thoughtful comments and suggestions provided by three anonymous reviewers. Correspondence concerning this article should be addressed to Timothy J. Trull, Department of Psychology, University of Missouri-Columbia, 210 McAlester Hall, Columbia, Missouri 6521 I. 232 ual of Mental Disorders, third edition (DSM-III; American Psychiatric Association, 1980) were introduced by Morey, Waugh, and Blashfield (1985). The MMPI-BPD scale consists of 22 true-false items that were judged to represent DSM-IIIcriteria for BPD and that discriminated between high- and low-scorers on the total scale score. Several studies have demonstrated that the MMPI-BPD scale discriminates between patients diagnosed with BPD and patients receiving other personality disorder diagnoses (e.g., Dubro & Wetzler, 1989; Mores Blashfield, Webb, & Jewell, 1988). The discrimination of BPD from other personality disorders is of substantial interest (Morey & Smith, 1988). However, the MMPI-BPD scale's ability to discriminate between BPD and Axis I diagnostic groups has not yet been reported despite the fact that the overlap of BPD and Axis I diagnostic groups, especially mood disorders, has been the subject of much research and controversy (e.g., Akiskal, Yerevanian, Davis, King, & Lemmi, 1985; Gunderson & Elliot, 1985; Widiger, 1989). A number of researchers have posited a close relationship between BPD and mood disorders. For example, Akiskal et al. (1985) reported that comparisons ofphenomenology, biological markers, family history, and outcome between BPD and mooddisordered groups suggest that BPD may in fact represent a "subaffective" disorder, making distinctions between mood disorders and BPD difficult. In addition to the clinical overlap between mood disorders and BPD, differentiating these disorders on the basis of self-report inventory scores may be difficult because state mood factors (especially depression) appear to have a substantial effect on self-reports of personality (Hirschfeld et al., 1983; Reich et al., 1986). Several researchers have suggested that acute mood symptoms may cause psychiatric patients to overreport realadaptive personality traits. For example, Hirschfeld et al. (1983) assessed depressed patients before and after treatment and reported that self-ratings of personality changed significantly following the alleviation of depressive symptoms. Although depressed, patients tended to score in a more pathological direc-

MMPI-BPD SCALE 233 tion on ratings of personality features. These results were in contrast to a control group of depressed patients whose depressive symptoms persisted after treatment and whose self-ratings of personality remained fairly consistent. Finally, there is also some evidence that self-reports of BPD symptoms may be state dependent (Hurt et al., 1984; Piersma, 1987), potentially clouding any distinction between BPD and mood disorders. In summary, results from previous studies raise the question of whether BPD patients and patients diagnosed with Axis I disorders (especially mood disorders) can be discriminated on the basis of their self-reports on the MMPI. The present study addressed this question in three ways. First, the mean MMPI clinical scale scores of BPD inpatients were compared with those scores from patients in one of several Axis I and Axis II comparison groups. Second, the discriminant validity of several MMPI codetypes previously identified as suggestive of a BPD diagnosis was evaluated. Finally, the reliability and discriminant validity of the MMPI-BPD scale were evaluated by (a) examining the internal consistency of the MMPI-BPD scale in a large psychiatric sample, and (b) assessing this scale's convergent and discriminant validity in a sample of psychiatric inpatients with various Axis I and Axis II diagnoses. In contrast to previous studies, the MMPI-BPD scores of clinically diagnosed BPD patients were compared with the scores of several DSM-III-R (American Psychiatric Association, 1987) diagnostic comparison groups: (a) major depression or dysthymia, (b) bipolar disorder or cyclothymia, (c) schizophrenia or schizoaffective disorder, and (d) other (non-bpd) personality disorders. Method The total sample comprised 395 consecutive adult psychiatric inpatients who were admitted to the acute-care units at a university medical center in a large metropolitan area, who completed the MMPI shortly after admission (typically within 1 week), and who did not meet exclusionary criteria for the study. Patients were excluded from the study if they omitted more than 30 questions on the MMPI or were less than 18 years old. Discharge diagnoses were assigned to all patients according to the diagnostic criteria of the DSM-111-R. Diagnoses were made by the treating therapist after extensive consultation with a team of psychiatrists, residents and interns, and psychologists. All team members had observed and interacted with the patient in question, and clinicians at this institution have been trained extensively in the use of DSM-III-R. This method of diagnostic practice approximates the LEAD (Longitudinal Expert evaluation using All Data) standard of diagnosis (Skodol, Rosnick, Kellman, Oldham, & Hyler, 1988; Spitzer, 1983). Previous comparisons of discharge diagnoses and diagnoses resulting from systematic chart review at this hospital have shown that these two methods are comparable (Fyer, Frances, Sullivan, Hurt, & Clarkin, 1988). Each MMPI was scored on the traditional clinical scales as well as on the Morey et al. (1985) MMPI-BPD scale. Consistent with previous studies, the 22-item (overlapping) version of the MMPI-BPD was used, and the raw MMPI-BPD scale scores were used as the dependent variable in the analyses involving this scale. Patient scores on the MMPI-BPD items were not known to the team members because these scores were calculated by me after the patient was discharged and were not presented in any of the psychological test reports. From the total sample, several comparison groups were formed: those receiving a primary Axis I diagnosis of major depression or dysthymia but not BPD on Axis II (MD; n = 70); those receiving a primary Axis I diagnosis of bipolar disorder or cyclothymia but not BPD on Axis II (BC; n = 36); those receiving a primary Axis I diagnosis of schizophrenia or schizoaffective disorder but not BPD on Axis II (SZ; n = 96); and those receiving a primary Axis II diagnosis of BPD (n = 61). The MMPI scale scores and MMPI-BPD scores of the Axis I diagnostic groups were compared with those of the borderline group. In separate analyses, MMPI clinical scale scores and MMPI-BPD scores of the BPD group were compared with those from a comparison group composed of patients receiving a personality disorder diagnosis other than BPD (OPD; n = 63). These latter analyses were conducted separately because approximately one half of the OPD patients were also included in the Axis I comparison groups. Diagnoses in this OPD group included nine non-bpd personality disorder diagnoses (passive-aggressive personality disorder was not represented) as well as the DSM-III-R diagnosis of personality disorder not otherwise specified. Results Table 1 presents the demographic and diagnostic characteristics of the total sample. The mean age of the total sample was 31.37 years; 61% of the sample was female, 82% of the sample was White, and the median length of stay in the hospital was 27.00 days. The comparison groups differed on a few of the demographic variables. The BPD group had a significantly higher proportion of women than did all other comparison groups (all p's <.05), and the MD group contained a significantly higher proportion of women than did the SZ group (p <.05). Only two other significant differences were found: The BPD group was significantly younger than the MD group (p <.05), and the SZ group had a longer length of stay in the hospital than did the MD group (p <.05). Table 2 presents comparisons of the mean K-corrected MMPI scale scores of the BPD group and the Axis I diagnostic groups. These groups were compared on each MMPI scale through an analysis of variance (ANOVA), and significant findings were followed up with post hoe Scheff6 t tests for pairwise comparisons. Age was significantly related to scale scores on F, Table 1 Demographic and Diagnostic Characteristics of Total Sample (iv = 395) % of Variable n sample Age (years) M = 31.37 (SD = 10.12) Sex Male 156 39 Female 239 61 Race White 324 82 Black 33 8 Hispanic 29 7 Other 9 3 Length of stay Mdn = 27.00 days Primary Axis I diagnosis Bipolar disorder or cyclothymia 39 10 Major depression or dysthymia 87 22 Schizophrenia or schizoaffective 99 25 Primary Axis II diagnosis Borderline 61 15 Other personality disorder 63 16

234 TIMOTHY J. TRULL 4, 6, 8, and 9. Therefore, analyses for these scales used age as a covariate. Consistent with previous findings, mean MMPI scale scores for the BPD group were >--70T on the Fscale as well as 6 of the clinical scales, indicating a high degree of overall profile elevation. Significant differences between groups were found for 8 of the 13 MMPI scales. With regard to the clinical scales, BPD patients scored significantly higher than did both the SZ and BC patients on Scales 2, 3, 4, and higher than the BC patients did on Scale 0 (all p's <.05). In addition, patients diagnosed with BPD scored significantly lower on Scale 5 than did SZ patients. Interestingly, the MD and BPD patients did not obtain significantly different scores on any MMPI clinical scale. In summary, only 5 of the 10 MMPI clinical scales discriminated between BPD patients and SZ or BC patients, and the BPD and MD groups were not distinguishable on any MMPI scale. Table 3 presents the comparisons between the BPD and the other personality disorders (OPD) group (i.e., Axis II). Age was significantly related to scores on Scales 3 and 9, and therefore was used as a covariate in these respective analyses. Significant differences were found only for Scales K and 5 (both p's <.05), with the OPD group scoring significantly higher on both of these scales. In their review of MMPI research on BPD, Morey and Smith (1988) listed six codetypes that were frequently observed in BPD patients. The sensitivity, specificity, positive predictive power (PPP), and negative predictive power (NPP) of these codetypes for the BPD diagnosis were examined in the present sample. Sensitivity is the proportion of BPD patients producing the respective MMPI codetype; specificity is the proportion of non-bpd patients not producing the codetype; PPP is the conditional probability ofa BPD diagnosis given the MMPI codetype; and NPP is the conditional probability of not receiving a BPD diagnosis given that one does not produce the MMPI codetype. Table 4 presents these results using only the patients composing the BPD, MD, BC, SZ, and OPD comparison groups (n = 298). The total number of subjects in these analyses is less than 328 because some patients in the OPD group also received an Axis I diagnosis of MD or BC. All codetypes had moderate sensitivity (SENS) and specificity (SPEC), low positive predictive power (PPP), and high negative predictive power (NPP). Of particular interest are the low PPP values, because this index is directly related to the diagnostic decision-making process that confronts the clinician when viewing an MMPI codetype. The last column in Table 4 presents the odds ratio contrasting the prevalence ofa BPD diagnosis given the codetype with the prevalence ofa BPD diagnosis in those not producing the MMPI codetype (Fleiss, 1981). The odds ratio approximates relative risk and was calculated as a/b divided by c/d, in which a = prevalence of BPD diagnosis in group with particular codetype, b = 1 - a, c = prevalence of BPD diagnosis in group without particular codetype, d = 1 - c (Fleiss, 1981). An odds ratio of 1 would indicate no association between a BPD diagnosis and a codetype, whereas an odds ratio of two would indicate that the odds of a person producing a particular codetype and receiving a BPD diagnosis is twice that of a person not producing the codetype. The statistical significance of each odds ratio was tested by computing a chi-squared statistic with one degree of freedom (Fleiss, 1981). As indicated, no odds ratio was significant, suggesting that these codetypes were not specific indicators of the BPD diagnosis (i.e., these codetypes were also prevalent among patients in the other diagnostic groups). Finally, the MMPI-BPD scores of the sample were considered. Using data from the total sample (n = 395), the internal consistency coefficient (KR-20) of the MMPI-BPD scale was calculated, and it equaled.69. This value is approximately equal to that obtained by Morey et al. (1985) in the original validation Table 2 K-corrected Minnesota Multiphasic Personality Inventory T Scores for Borderline Personality Disorder (BPD), Major Depression or Dysthymia (AID), Bipolar Disorder or Cyclothymia (BC), and Schizophrenia or Schizoaffective Disorder (SZ) Diagnostic Groups BPD MD BC SZ (n = 61) (n = 70) (n = 36) (n = 96) Significant Scale M SD M SD M SD M SD F contrasts L 48.30 7.30 50.00 7.71 49.22 8.32 53.04 9.37 4.73** SZ > BPD F 72.77 16.00 69.09 14.43 67.08 17.31 74.04 18.44 1.70 K 49.16 9.41 51.26 9.33 52.33 10.82 52.19 9.32 1.43 1 64.30 13.72 68.00 14.02 62.03 16.60 62.09 13.90 2.62 2 80.43 14.49 84.90 16.17 67.22 18.98 71.10 16.43 14.75"** MD, BPD> SZ, BC 3 70.05 11.35 72.50 11.95 61.56 13.84 63.88 11.16 11.14"** MD, BPD > SZ, BC 4 79.75 12.94 76.31 13.39 69.81 13.10 73.67 10.84 5.41"** BPD > SZ, BC 5 49.90 15.15 54.73 16.44 56.50 15.16 60.15 13.76 5.96*** SZ> BPD 6 73.15 11.87 72.87 12.38 68.39 13.59 71.70 15.10 1.23 7 72.34 13.03 77.73 14.06 65.78 17.83 70.45 14.87 6.05*** MD> SZ, BC 8 79.20 16.44 79.59 17.43 73.17 19.75 80.12 19.42 1.64 9 63.87 11.97 59.86 11.15 68.31 13.18 65.40 14.08 3.48* BC> MD 0 62.70 12.24 64.94 11.16 53.28 11.71 58.49 9.92 10.73"** MD, BPD > BC MD > SZ Note. Analyses of variance for Scales F, 4, 6, 8, and 9 used age as a covariate (i.e., these were ANCOVA~s). *p<.05. **p<.01. ***p<.001.

MMPI-BPD SCALE 235 Table 3 K-corrected Minnesota Multiphasic Personality Inventory Scores for Borderline Personality Disorder (BPD) and Other (Non-BPD) Personality Disorder (OPD) Diagnostic Groups BPD OPD (n = 61) (n = 63) Scale M SD M SD F L 48.30 7.30 50.49 7.74 2.64 F 72.77 16.00 70.86 15.19 0.47 K 49.16 9.41 53.29 9.67 5.78* 1 64.30 13.72 68.63 16.21 2.58 2 80.43 14.49 80.60 19.94 0.00 3 70.05 11.35 71.08 13.50 0.01 4 79.75 12.94 77.79 12.85 0.72 5 49.90 15.15 60.00 14.86 14.04"* 6 73.15 11.87 71.27 13.30 0.69 7 72.34 13.03 75.48 18.19 1.21 8 79.20 16.44 80.16 19.21 0.09 9 63.87 11.97 64.92 10.66 0.98 0 62.70 12.24 59.84 13.06 1.59 Note. Analyses of variance for Scales 3 and 9 used age as a covariate (i.e., these were ANCOV~s). *p<.05. **p<.001. study (KR-20 =.71). The mean score on the MMPI-BPD scale for the entire sample (n = 395) was 10.67 (SD = 3.83). As for correlates of the MMPI-BPD scores, only age covaried significantly (r = -. 18, 17 <.01); in general, MMPI-BPD scores were higher for younger psychiatric inpatients. Because of this significant association, age was used as a covariate in analyses involving MMPI-BPD scores. The mean MMPI-BPD score for each of the comparison groups is presented in Table 5. Also presented are results of the respective analyses of covariance (AN- COVAs) and the results of post hoc Scheff6 tests. An ANCOVA (with age as a covariate) comparing the MMPI-BPD scores of the MD, BC, SZ, and BPD groups was significant, F(3, 258) = 6.82, p <.001. Post hoc Scheft'6 tests revealed that only the BPD and SZ groups differed significantly on MMPI BPD scores. A separate comparison between BPD patients and OPD patients was made. An ANCOVA (with age as a covariate) was significant, F(1,121) = 6.55, p <.05, indicating that the BPD and OPD groups differed significantly on MMPI-BPD scores. As Morey and Smith (1988) have noted, one important aspect of the M MPI-BPD scale that is in need of further evaluation is that of appropriate cutoff points. T scores for the MMPI-BPD scale have been developed using normative data from the original validation study. Previous studies (e.g., Dubro, Wetzler, & Kahn, 1988) have used a T-score of 70 or more on the MMPI- BPD (raw score > 15) to indicate the presence of BPD. In the present study, using a cutoff of 70T resulted in a sensitivity rate of.25, a specificity rate of.83, a PPP rate of.27, and an NPP rate of.91. The odds of producing an MMPI-BPD score at or above 70T and receiving a BPD diagnosis was 1.61. Comparing these diagnostic efficiency rates to those presented in Table 4 reveals that the MMPI-BPD scale appears to be a more conservative indicator of a borderline diagnosis than the MMPI codetypes. The MMPI-BPD is a much less sensitive but a more specific measure of a borderline personality disorder diagnosis. False positives were minimized at the expense of false negatives. A final analysis involved examining cutoff scores on the MMPI-BPD scale with regard to sensitivity, specificity, and agreement with clinical diagnosis. Table 6 presents these data. As can be seen, a cutoff score ofl 3 on the MMPI-BPD resulted in the highest diagnostic agreement (i.e., kappa) between the MMPI-BPD and clinical diagnosis. A cutoffofl 3 versus 15 (i.e., > 70T) resulted in higher sensitivity, lower specificity, and higher diagnostic agreement. However, the overall rate of diagnostic agreement (kappa =. 19) for a cutoff of 13 was quite low. Discussion In this study, BPD patients obtained significantly higher MMPI scores than did the schizophrenia/schizoaffective (SZ) Table 4 Sensitivity, Specificity, Positive Predictive Power, Negative Predictive Power, and Odds Ratios of MMPI Codetypes Hypothesized to Indicate the Presence of Borderline Personality Disorder and of a Cutoff Score of 70T on the MMPI-BPD Scale Positive Negative predictive predictive Sensitivity Specificity power power Odds ratio MMPI codetype 2, 4, and 8 >-- 70T.52.60.25.83 1.65 2 and 7 > 70T.51.51.21.80 1.06 2 and 8 > 70T.57.52.24.83 1.48 4 and 8 >-- 70T.59.53.24.83 1.61 6 and 8 > 70T.59.54.25.84 1.69 7 and 8 > 70T.56.51.22.82 1.29 MMPI-BPD >- 70T (raw score > 15).25.83.27.91 1.61 Note. MMPI-BPD = Minnesota Multiphasic Personality Inventory-Borderline Personality Disorder scale. No odds ratio significant at p <.05. N = 298, includes all borderline personality disorder, major depression or dysthymia, bipolar disorder or cyclothymia, schizophrenia or schizoaffective disorder, and other personality disorder patients.

236 TIMOTHY J. TRULL Table 5 Comparison of Diagnostic Groups on the MMPI-BPD Scale Raw MMPI- BPD score Diagnostic group n M SD ANCOVA F Comparison with Axis I groups Borderline (BPD) 61 12.56 3.49 6.82"** Bipolar/cyclothymia 36 11.11 3.47 Major depression/dysthymia 70 10.97 3.68 Schizophrenia/schizoaffective (SZ) 96 9.74 3.80 Comparison with Axis II group Borderline 61 12.56 3.49 6.55* Other personality disorder (OPD) 63 10.83 3.74 Significant contrast BPD > SZ BPD > OPD Note. MMPI-BPD = Minnesota Multiphasic Personality Inventory-Borderline Personality Disorder scale; ANCOVA = analysis ofcovariance. * p <.05. *** p <.001. or bipolar/cyclothymia (BC) patients on four clinical scales. No significant differences, however, were found between the BPD and major depression/dysthymia (MD) groups on any of the MMPI clinical scales. As for the OPD group, significant differences were found for Scales K and 5, with the OPD group scoring higher than the BPD group in both cases. The diagnostic efficiency rates (SENS, SPEC, PPP, and NPP) for each MMPI codetype thought to be indicative ofa BPD diagnosis were approximately equal. PPP values for these codetypes were consistently low; there was little improvement over the base rate of the BPD diagnosis (prevalence =.20). Therefore, an examination of the traditional MMPI scale scores and several codetypes did not reveal any pattern of scores distinctive to the BPD diagnosis, and scores on the traditional MMPI scales did not differentiate BPD from depressive disorders or from other personality disorders. Results from the present study suggest that Morey et al?s (1985) MMPI-BPD scale discriminates those clinically diagnosed as BPD from those diagnosed as SZ, as well as from those diagnosed as OPD. In both cases, BPD patients scored signifi- Table 6 Cutoff Scores on the Minnesota Multiphasic Personality Inventory-Borderline Personality Disorder Scale (MMPI-BPD) Raw MMP1-BPD score Sensitivity Specificity Kappa z9.88.33.11 zl0.79.44.13 ~11.72.52.15 ~12.64.61.17 ~13.56.69.19 ~14.39.76.14 ~15.25.83.08 ~16.20.90.ll ~17.13.93.08 ~18.08.97.07 ~19.07.99.09 ~20.00 1.0.03 Note. N = 298, includes all borderline personality disorder, major depression or dysthymia, bipolar disorder or cyclothymia, schizophrenia or schizoaffective disorder, and other personality disorder patients. cantly higher on this MMPI scale than did patients in the SZ and OPD groups. This latter result is consistent with previous studies that have compared the MMPI-BPD scores of BPD and OPD groups (Dubro & Wetzler, 1989; Morey et al., 1988). It should also be noted that the MMPI-BPD scale does not appear to be measuring only severity of psychiatric symptoms because scores did discriminate between the BPD and SZ groups, with the SZ group scoring significantly lower on this scale. Finally, the NPP of the MMPI-BPD cutoff score of 70T was higher than that of the MMPI codetypes, indicating that the MMPI-BPD may be more useful in ruling out a BPD diagnosis. In the present study, however, MMPI-BPD scores failed to discriminate BPD patients from those diagnosed with a mood disorder on Axis I and no BPD diagnosis on Axis II. High scores on the MMPI-BPD scale were obtained by those suffering from mood disorders as well as BPD; the average scores of these patients were approximately one or more standard deviations above the mean score of the normative sample group used in the development of the MMPI personality disorder scales (Morey & Smith, 1988). These results support the contentions of Akiskal et al. (1985) and Widiger (1989) that the BPD and mood disorder constructs overlap such that differentiation between the two proves difficult. Results suggest that the MMPI- BPD scale may measure a general construct ofaffectivity, characterized by symptoms of both depressive disorders and bipolar/cyclothymic disorders. Supporting this hypothesis, an examination of the M MPI-BPD scale reveals that many items assess affective features of BPD (e.g., I cry easily [True], I very seldom have spells of the blues [False], I brood a great deal [True], and I am not easily angered [False]). Therefore, it appears that many of the current MMPI-BPD items are as characteristic of a mood disorder as they are of borderline pathology. It is not surprising then that the MMPI-BPD scale fails to differentiate borderline and mood pathology. Assuming that the distinction between BPD and mood disorder constructs is indeed a valid one, a scale to differentiate between BPD and mood disorders could be constructed by emphasizing MMPI items that are shown to empirically discriminate between these disorders. Viewed from an empirical

MMPI-BPD SCALE 237 perspective on scale construction, the purpose of a self-report scale (such as the MMPI-BPD) is not to describe or to characterize the disorder's symptomatology, but rather to optimize differential diagnosis (Wiggins, 1973). Consistent with this approach, MMPI items assessing nonaffective features of BPD would be emphasized in a scale designed to differentiate BPD from mood disorders. For example, BPD features such as"identity disturbance;' "impulsivity," and perhaps "pattern of unstable/intense interpersonal relationships" might be represented by more items than the affective features of BPD in such a scale. Morey et al's (1985) MMPI-BPD items do not appear to sample these three features of the borderline construct adequately, whereas affective features of BPD appear to be overrepresented. It is, of course, conceivable that a scale constructed to differentiate BPD from mood disorders may not differentiate BPD from other disorders. Several scales or subscales may be necessary because it is unreasonable to expect one set of items to be optimal for ruling out all possible diagnostic alternatives. For example, the items that optimally discriminate BPD from mood disorders will not likely be the same as the items that best differentiate BPD from schizotypal personality disorder. In general, it appears that alternative sets of self-report items are needed to address questions regarding various differential diagnoses (Widiger & Trull, 1991). There are a few potential limitations to the current study that should be discussed. The results from the present study would have been expected if there was a high comorbidity rate for mood disorder in the BPD group. An examination of the Axis I comorbid diagnoses, however, revealed that only three BPD's (5%) received a diagnosis of bipolar disorder or cyclothymia on Axis I, and 17 (28%) received an Axis I diagnosis of major depression or dysthymia. Therefore, only about one third of the BPD patients received comorbid mood disorder diagnoses. To explore this issue further, an additional analysis was performed in which scores from a "pure" BPD group (i.e., those patients who did not meet criteria for any other Axis I or I! disorder, n = 19) were compared with the MD, BC, and SZ groups. The same pattern of results emerged; only the BPD and SZ groups were discriminable on the basis of the MMPI-BPD scores. Therefore, it appears that comorbid mood disorder diagnoses in some BPD patients do not completely account for the pattern of resuits obtained in the present study. The present study is limited by its reliance on hospital discharge diagnoses, which could be criticized as potentially unreliable and fallible. The diagnoses in this study were made only after extensive consultation with all team members and represent the consensus of a number of professionals from a variety of disciplines. Thus, it is likely that these diagnoses are more reliable than a diagnosis assigned by only one professional. In addition, Fyer et al. (1988) found a high level of convergence between discharge diagnoses at this hospital and those diagnoses assigned following a systematic chart review. Nevertheless, the results should be replicated in groups of psychiatric patients diagnosed by structured interview, Although the present study raises the issue of the overlap between the BPD and mood disorder constructs, additional studies using different research designs (e.g., concurrent assessments of mood, assessments when patients are not in an acute state) will be necessary to ultimately address whether these constructs can be disentangled. The MMPI-BPD items were retained in the recent revision of the MMPI, the MMPI-2 (Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989). Therefore, researchers using the MMPI-2 can calculate scores on the MMPI-BPD scale and determine which differential diagnoses are best addressed by this scale. Future research might also examine individual MMPI-2 items to determine if a subset of these would aid in the discrimination between BPD and mood disorders. As previously noted, this has been a difficult differential diagnosis. It may in fact be the case that the BPD and mood disorder constructs are hopelessly intertwined because of an overlap in diagnostic features (Akiskal et al., 1985; Widiger, 1989). It is conceivable, however, that some assessment instruments may be able to differentiate BPD and mood disorders. Future studies should also examine the discriminant validity of other selfreport measures of BPD (e.g., the Millon Clinical Multiaxial Inventory-II Millon, 1987; the PDQ-R; Hyler & Rieder, 1987) to determine whether these instruments can differentiate BPD and mood disorders. In summary, the present study suggests that borderline patients can be distinguished from schizophrenia-schizoaffective patients on the basis of MMPI clinical scale scores as well as scores on the MMPI-BPD scale. MMPI clinical scale scores were helpful in distinguishing borderlines from bipolar-cyclothymia patients; however, the MMPI-BPD scale scores for these two groups were not significantly different. The OPD group was best differentiated from the borderline group by their respective MMPI-BPD scores. Finally, the MMPI scales and the MMPI-BPD scale failed to discriminate between the major depression-dysthymia group and the borderline group. Whether these latter two groups of patients can be differentiated by means of self-report psychological test scores remains to be demonstrated. References Akiskal, H. S., Yerevanian, B. I., Davis, G. C., King, D., & Lemmi, H. (1985). The nosologic status of borderline personality: Clinical and polysomnographic study. 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