Journal of Behavioral Medicine, Vol. 20, No. 4, 1997

Identification of Beck Depression Inventory ItemsRelated to Multiple Sclerosis

The percentage contribution of each item on the Beck Depression Inventory(BDI) to the total BD1 score was compared across patients with multiplesclerosis (MS), patients diagnosed with major depressive disorder, and normalcollege students. We considered an item to be confounded by MS-relatedsymptoms if its percentage contribution to the total BDI score was significantlygreater in the MS group than the major depression and control groups. Itemsmeasuring work difficulty, fatigue, and concerns about health met this criterion.These items accounted for 34, 17, and 19% of the total BDI score in the MS,major depression, and control groups, respectively. Using the 18-item BDI(BDI-18) which resulted from excluding the 3 confounded items, MS patientsfound to be were more depressed than controls but less depressed than themajor depression group. The identification of signs of depression notconfounded with MS which could be substituted for confounded signs wasalso discussed.KEY WORDS: multiple sclerosis; depression; assessment.

1University of California, San Francisco.2Kaiser Pennanente Medical Care Group of Northern California.3University of California, Santa Barbara.4Pacific Graduate School of Psychology.5To whom correspondence should be addressed at UCSF/Mt. Zion MS Center, 1600Divisadero Street, San Francisco, California 94115-1642.

David C. Mohr,1,4,5 Donald E. Goodkin,1 William Likosky,2Larry Beutler,3 Nicole Gatto,1 and Michele K. Langan4

Accepted for publication: January 27, 1997

407

OlW-TnvmnOMMOTSlUM) O 1997 PIMVB PUMMU* Ompontioa

Multiple sclerosis (MS) affects between 250,000 and 350,000 peoplein the United States (Anderson et al., 1992). Patients may experience awide range of symptoms including tingling, numbness, weakness, loss ofcoordination, imbalance, incontinence, blurred vision, pain, fatigue, andcognitive impairment (Smith et al., 1993). Symptoms are often associatedwith a reduction in quality of life (Rudick et al., 1992), ability to work (Raoet al., 1991), and compliance with medical treatment protocols (Mohr etal., 1997). Depression is also common, with point prevalence rates rangingfrom 14 to 54% (Minden and Schiffer, 1990; Schubert and Foliart, 1993).

In the clinical care of MS patients reliable and valid assessment ofdepression is useful to screen for depression and to monitor treatments.Assessment of depression is also essential for research in evaluating treat-ments for depression, reactions to medical interventions, and epidemiology.Assessment has been complicated, however, by the numerous overlappingsymptoms. For example, of the nine symptoms related to a DSM-IV(American Psychiatric Association, 1994) diagnosis of major depressive dis-order (MDD), four are also common symptoms of MS, including fatigue,psychomotor retardation, decreased concentration, and insomnia or hyper-somnia. Self-report measures often include questions regarding healthconcerns and diminished ability to work, which are also very common inprogressive neurologic disorders such as MS. Thus, any measure of depres-sion that includes items assessing fatigue, sleep problems, decreases inconcentration, work difficulty, or health concerns may overestimate theprevalence and severity of depression in patients with MS.

The Beck Depression Inventory (BDI; Beck et al., 1961), originally de-signed to measure level of depression in patients receiving cognitive-behav-ioral psychotherapy, is widely used as a self-report measure of dysphoria inpatients with MS. The BDI has also been suggested as a screening devicefor clinical depression in MS clinics (Sullivan et al., 1995). However, theBDI composite score is potentially confounded by self-reports of fatigue,insomnia, work difficulty, and concerns about health.

The pattern of responses to individual items of the BDI has not beenrigorously studied. Huber et al. (1993) investigated the relative contributionof physical symptoms to the overall BDI score by comparing the frequencyof responses to individual items of the BDI in MS patients and normalcontrols. Significant differences between the MS group and the normal con-trols in the frequency of item endorsement was found on 11 items assessinga broad range of symptoms including mood, self-reproach, vegetative signs,and somatic problems. However, Huber et al. did not control for severityof depression in MS patients and, as a result, were not able to determine

408

INTRODUCTION

Mohr et al.

if some BDI items were endorsed more frequently because of disease re-lated impairment or severity of depression. Additionally, a group ofnon-MS patients who were depressed was not included for comparison.

Nyenhuis et al. (1995) compared BDI and Multiscale Depression In-ventory (MDI) scores in MS outpatients, outpatients with depression, andnormal subjects. MS patients scored significantly higher than the normalsubjects and Sower than the depressed group on both measures. However,there was no difference in the mood subscale of the MDI between MSpatients and normal subjects, suggesting that elevated scores on measuresof depression for MS patients may be due in part to items assessing otherfactors.

There have been efforts to evaluate the effects of other chronic con-ditions on measures of depression, most notably chronic pain. Wesley et al.(1990) found that the 11 items of the BDI which they identified as a so-matic subscale were related to pain intensity, while the 6 items theyidentified as a cognitive/affective subscale were not. Williams and Richard-son (1993) found that the most frequently identified BDI items amongchronic pain patients were those which loaded onto a somatic factor. How-ever, it is unclear if these response patterns diverge from those seen indepressed patients since neither study employed a depressed comparisongroup.

The purpose of this study is to identify those items on the BDI whichdo not measure the same constructs in MS patients as they do in patientswith major depression or in normal controls.

This study compared 184 patients with MS, 72 patients diagnosed withmajor depression, and 555 college students. Of the 184 MS patients, 101were seen at the University of California at San Francisco Multiple Scle-rosis Center (UCSF), and 83 were seen in the Department of Neurologyat Kaiser Pennanente. All MS patients had clinically or laboratory sup-ported definite MS (Poser et al., 1983). The 72 patients diagnosed withcurrent major depressive were part of an NIMH funded depression studyat the University of Arizona (Beutler et al., 1991). All depressed patientswere diagnosed by an advanced graduate student, psychologist, or psychia-trist, and the diagnosis was validated by a standardized, computerinteractive administration of the National Institute for Mental Health's Di-agnostic Interview Schedule (DIS; Robins et al., 1981). Five hundredfifty-five college students enrolled in an introductory psychology class atthe University of Arizona served as a normal college student control group.

409EDI Items Related to Multiple Sclerosis

METHODS

The college student control group was used due to availability of subjectsand because college students are one of the most widely studied groupsusing the BDI.

The mean ages for the MS patients, the depressed patients, and thenormal college student control group were 44,0,47.5, and 20.2, respectively.Among the MS sample there were 59 men and 125 women. Among thedepressed sample there were 35 men and 37 women, while the normal col-lege student control group consisted of 249 men and 306 women. Amongthe MS patients, 22 where wheelchair bound, 72 required some assistanceambulating, and 90 could walk without aids.

Beck Depression Inventory (BDI). The BDI (Beck et al., 1961) is oneof the most widely used self-report measures of depression. It consists of21 symptoms related to depression, each of which is self-rated from 0 (ab-sent) to 3 (severe).

Criteria for Identification of BDI Items Which Are MS Related. A seriesof analyses of variance (ANOVAs) was performed comparing the percent-age contribution of each BDI item to the total BDI score (BDI item/BDItotal score) across MS, depressed, and a normal college student population.Using an a level of .05, a Bonferroni adjustment for a slippage due tomultiple analyses requires the use of a .0023 level of significance. For analy-ses of items reaching significance, both the depressed group and the normalcollege student control group each were compared individually to the MSgroup using the Newman-Keuls method. A BDI item was determined tobe related to the subject's status as an MS patient if two criteria were met:(1) there was a significant difference (p < .0023) across diagnostic groupsfor the BDI item/total score, and (2) the BDI item/total score was foundto be significantly higher among MS patients than among nonmedical pa-tients with diagnoses of major depression and normal college students.

The mean BDI scores for the MS group, the depressed group, andthe college student control group were 10.6, 30.9, and 6.8 respectively,which a one-way ANOVA found to be significant [F(2,810) = 377.0, p <.0001]. Newman-Keuls post hoc analyses revealed that each of the threegroups differed significantly from the other two, with all p values being<.0001.

The next analysis was designed to determine the relative importanceof each symptom in determining the total BDI score and to compare therelative contribution of each BDI item to the overall BDI score across thethree groups. Because the three groups differed so significantly in overall

410 Mohr et al.

RESULTS

BDI scores, it was expected that comparisons of individual BDI itemsacross groups would be powerfully influenced by the overall level of de-pression. That is, for each item the depressed group would be higher thanthe MS group, which would be higher than the control group. These dif-ferences would be reflections more of overall level of depression, ratherthan a reflection of the relative importance of each symptom in determiningthe depression score. To address this problem a percentage score was cal-culated, dividing the score on the individual item by the overall BD! score.This percentage score controlled for overall level of depression.

The percentage scores for each item were compared across groups us-ing a series of one-way ANOVAs. The results of this analysis are presentedin Table I. Three BDI items met the criteria for being MS related. Theseincluded fatigue, work difficulty, and concerns about health. Compared tothe depressed group, the MS group showed significantly lower levels ofcomparative responding on 6 of the 21 items. On five of these six items(items 2, 3, 5, 6, and 13) there was no difference between the MS groupand the normal college student control group. Thus, for those items as-sessing discouragement, feelings of failure, guilt, and decision-makingproblems, the MS group responses were significantly lower than the de-pressed group's but similar to the control group's. The percentage scoresfor irritability were similar to the normal college student controls' buthigher than those for the depressed group.

Because three items met the criteria for being MS related, the BDIwas recalculated for all groups using the remaining 18 items, which arereferred to as the BDI-18. The mean BDI-18 scores were 7.4 for the MSgroup, 25.8 for depressed patients, and S.5 for the control group. Thesedifferences were significant for all groups [F(2,810) = 478.75, p < .0001].Newman-Keuls comparisons showed significant differences between allgroups.

Our results support the notion that among MS patients the compositeBDI score is significantly confounded by MS-related symptoms (LaRoccaet al., 1993). Three items measuring work problems, fatigue, and concernsabout health were found to be related to the subject's MS according tothe predetermined criteria. Fatigue is one of the most common symptomsof MS (Smith et al., 1993). Problems at work are also common sequelaeof physical and cognitive impairments associated with MS (Rao et al., 1991).Concerns about one's health are expected in patients with chronic illnesses.Insomnia was not related to the MS diagnosis. This is further support for

411BDI Items Related to Multiple Sclerosis

DISCUSSION

Table I. Percentage of Contribution of Each Item to the Total BDI score

BDI item

1. Feeling sad2. Discouraged about future3. Feel like a failure4. Dissatisfied and bored5. Feeling guilty

6. Sense of being punished7. Disappointed in self8. Self-blame9. Suicidal thoughts

10. Crying spells

11. Irritability12. Social withdrawal13. Decision-making problems14. Body image15. Work difficulties

16. Sleep disruption17. Fatigue18. Appetite loss19. Weight loss20. Concerns about health

21. Loss of libido

MS(« = 184)n

3.92.80.96.61.3

1.02.14.62.12.9

8.42.13.13.5

10.7

7.815.42.13.57.7

6.7

Depressed(n = 72)a,b

5.15.5"**6.0****5.25.3****

3.7***'4.4"*5.94.35.2

4.3*4.15.8**4.16.2****

4.95.7****2.12.04.8**

5.1

Controls(n = 555)**

3.53.11.74.60.1

2.05.9****9.4***3.15.2

9.63.43.94.36.1****

6.010.6**4.9*5.42.6****

2.5****

ANOVAp value

.3601

.0230

.0000

.0367

.0000

.0005

.0000

.0000

.0916

.0252

.0068

.0833

.0268

.5593

.0000

.0969

.0000

.0004

.0609

.0000

.0000

"The percentage each item contributes to the total BDI score (BDI item/total BDI). Becauseof rounding in the analyses, the columns do not add up to exactly 100%.

bStatistical footnotes reflect Newman-Keuls post hoc p values for differences between MSgroup and depressed or control group.

*p < .05.**p < .01.

***p < .001.****p < .0001.

the notion that sleep disorders in MS are frequently related to depression(Clark et al., 1992). Responses to these three items contributed to 33.8,16.7, and 19.2% of the total BDI score in patients with MS, patients withmajor depression, and normal control subjects, respectively.

The overestimation of depression in MS patients by the BDI has im-portant consequences in the MS literature. Studies using the BDI to assessprevalence of affective disorders likely overestimate the occurrence of de-pression. It should be noted that the BDI is a less than ideal measure forassessing prevalence, as it more accurately measures subjective dysphoriarather than any DSM-related disorder (Coyne, 1994). The use of the BDIas an outcome measure may underestimate the effectiveness of interven-

412 Mohr et al.

tions designed to treat depression. If a large percentage of the total BDIscore is related to fatigue, work problems, and concerns about health, bothpre- and posttreatment levels of depression in MS patients may be inflated.Finally, the utility of the BDI as a screening device for depression in MSclinics (Sullivan et al., 1995) may be limited due to the confounding of MSsymptoms and dysphoria in the BDI scores.

This study also provides data useful for MS researchers who wish toaddress the issue of confounded symptoms in the diagnosis of MDD bysubstituting nonconfounded for confounded systems as suggested by Endi-cott (1984). According to the substitution approach, symptoms used in thediagnosis of MDD which are confounded with the symptoms of medicalillness may be removed from the menu and other diagnostic signs andsymptoms may be substituted. These data indicated that patients with MDDreported significantly more discouragement about the future, feeling likea failure, and disappointment in one's self than MS patients or college stu-dent controls. This suggests that these signs and symptoms may be usefulsubstitutes for confounded symptoms when diagnosing MDD in MS. How-ever, further validation using such substitute criteria in diagnosing MDDis required.

We conclude that (1) patients with MS are, on average, slightly butsignificantly more dysphoric than normal subjects and much less dysphoricthan patients meeting criteria for major depression, (2) the BDI signifi-cantly overestimates the level of dysphoria in patients with MS, and (3)the accuracy of the BDI as a measure of dysphoria in MS patients is im-proved by removing confounding items including work problems, fatigue,and concerns about health.

This research was supported by National Multiple Sclerosis Society Re-search Grant GR 2719A1/2 (Dr. Mohr) and a grant from the KaiserPermanente Medical Care Group of Northern California (Drs. Likosky andMohr).

American Psychiatric Association (1994). Diagnostic and Statistical Manual of Mental Disorders,4th ed., APA, Washington, DC.

Anderson, D. W., Ellenbeig, J. H., Leventhal, C M, Reingold, S. C., Rodriguez, M., andSilberberg, D. H. (1992). Revised estimate of the prevalence of multiple sclerosis in theUnited States. Ann. Neurol. 31: 333-336.

BDI Items Related to Multiple Sclerosis 413

ACKNOWLEDGMENTS

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