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Behaviour Research and Therapy 43 (2005) 1527–1542

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Psychometric validation of the obsessive belief questionnaireand interpretation of intrusions inventory—Part 2: Factor

analyses and testing of a brief version

Obsessive Compulsive Cognitions Working Group�,1

School of Social Work, Boston University, 264 Bay State Road, Boston, MA 02215, USA

Accepted 7 July 2004

Abstract

The Obsessive Belief Questionnaire (OBQ) and the Interpretation of Intrusions Inventory (III) weredesigned to assess beliefs and appraisals considered critical to the pathogenesis of obsessions. In previousreports we have described the construction and psychometric properties of these measures. In this study abattery of questionnaires assessing anxiety, depression, and obsessive compulsive symptoms was completedby 410 outpatients diagnosed with obsessive compulsive disorder, 105 non-obsessional anxious patients, 87non-clinical adults from the community, and 291 undergraduate students. Items from 6 theoreticallyderived subscales of the OBQ were submitted to factor analysis. Three factors emerged reflecting (1)Responsibility and threat estimation, (2) Perfectionism and intolerance for uncertainty, and (3) Importanceand control of thoughts. A 44-item version (OBQ-44) composed of high-loading items from the 3 factorsshowed good internal consistency and criterion-related validity in clinical and non-clinical samples.

see front matter r 2005 Elsevier Ltd. All rights reserved.

brat.2004.07.010

ding author: Gail Steketee. Tel.: +1 6173530815; fax: +1 6173535612.

ress: steketee@bu.edu.

Gail Steketee and Randy Frost. The members of the working group who contributed to this study are (in

rder): Sunil Bhar, Martine Bouvard, John Calamari, Cheryl Carmin, David A. Clark, Jean Cottraux,

amp, Elizabeth Forrester, Mark Freeston, Randy Frost, Celia Hordern, Amy Janeck, Michael Kyrios,

, Fugen Neziroglu, Caterina Novara, Gilbert Pinard, C. Alec Pollard, Christine Purdon, Josee Rheaume,

, Paul Salkovskis, Ezio Sanavio, Roz Shafran, Claudio Sica, Gregoris Simos, Ingrid Sochting, Debbie

il Steketee, Steven Taylor, Dana Thordarson, Patricia van Oppen, Ricks Warren, Maureen Whittal,

m, and Jose Yaryura-Tobias. Special thanks to Michael Kyrios, Steve Taylor, and Dana Thordarson for

ta analyses, to Cheryl Carmin for drafting the manuscript, and to Neil Rector for contributing additional

oject.

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Obsessive Compulsive Cognitions Working Group / Behaviour Research and Therapy 43 (2005) 1527–15421528

Subscales showed less overlap than original scales. Factor analysis of the III yielded a single factor,suggesting the total score be used in lieu of the 3 rationally derived subscales. The scales performed well ontests of convergent validity. Discriminant validity was promising; hierarchical regression analyses indicatedthat the OBQ subscales and III generally predicted OC symptoms after controlling for general distress. Arevision of the OBQ, the OBQ-44, is included in the appendix.r 2005 Elsevier Ltd. All rights reserved.

Keywords: Beliefs; Appraisals; Cognitive assessment; OCD; Responsibility; Perfectionism

Introduction

Recent theoretical and empirical work suggests that several cognitive constructs (e.g., inflatedresponsibility, overestimation of threat, thought-action fusion, intolerance of uncertainty) arerelevant to the development and exacerbation of obsessive-compulsive (OC) symptoms (Freeston,Rheaume, & Ladouceur, 1996; Frost & Steketee, 2002; Purdon, 2001). Cognitive strategies fortreating obsessive-compulsive disorder (OCD) have been based on the modification of key beliefsand appraisals formulated in these theories (Rachman, 1998; Salkovskis & Warwick, 1985; vanOppen & Emmelkamp, 2000; Whittal & McLean, 1999). Clearly, it is important to measurecognitive constructs hypothesized to be relevant to OCD. Many such measures have beendeveloped in recent years, but with little consensus regarding which domains to assess and verylimited psychometric information regarding these scales (Taylor, Kyrios, Thordarson, Steketee, &Frost, 2002).

To address these concerns a large group of international researchers, the Obsessive CompulsiveCognitions Working Group (OCCWG, 1997, 2001), identified domains considered central toOCD and developed the 87-item Obsessive Beliefs Questionnaire (OBQ) and the 31-itemInterpretation of Intrusions Inventory (III). Six rationally derived subscales of the OBQ-87(overestimation of threat, intolerance of uncertainty, importance of thoughts, control of thoughts,responsibility, and perfectionism) and the three subscales of the III-31 (control of thoughts,importance of thoughts, responsibility) showed good internal consistency but were highlyintercorrelated. Findings from initial testing provided preliminary evidence for the reliability andvalidity of these instruments, but further study of reliability and specificity of the measures usinglarger samples was needed.

Part 1 of this investigation (OCCWG, 2003) described the reliability and convergentand discriminant validity of the original, rationally derived subscales of the OBQ and IIIusing four samples who completed the English language version of the instruments.These included 248 participants with OCD as their primary (most severe) disorder (OC), 105anxious controls (AC), 87 community controls (CC) and 291 student controls (SC).Results indicated that the belief and appraisal dimensions represented by the OBQ and IIIsubscales showed good internal consistency and good test–retest reliability over a 2–3month interval. Findings for criterion-related (known-groups) validity based upon comparisonsof four subject samples were generally good. The OCs scored significantly higher than both non-clinical samples (SC and CC) on every subscale, and scored higher than ACs on 3 (Responsibility,Control, and Importance of thoughts) of the 6 OBQ subscales and 2 (Responsibility, Control of

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thoughts) of the 3 III subscales. Thus, beliefs related to Tolerance for Uncertainty, Over-estimation of Threat, and Perfectionism and appraisals related to Importance of Thoughtsappeared to be relevant but not specific to OCD.

As evident from their moderately high intercorrelations, the subscales of the OBQ and subscalesof the III overlapped, suggesting that the appraisal and belief domains measured by these scalesmay not be well differentiated from one another. Convergent validity was evident in the moderatecorrelations of almost all OBQ subscales, except Importance of Thoughts with measures of OCsymptoms, but the III showed a more variable pattern of association. With respect to discriminantvalidity, correlations of the cognitive measures with measures of non-OC symptoms (e.g.,depression and general anxiety) was approximately as high as those with OC symptoms. This lackof specificity was apparent in both OC and non-OC samples. To further clarify discriminantvalidity, a series of analyses were conducted to partial out the influence of other measures. TheOBQ and III showed a specific relationship with OC symptoms even after controlling for worry,but both instruments appeared to have relevance for other negative affective states, such as worry,and may not be unique to OCD.

The aim of the present paper is to report on a factor analysis of the OBQ and III using a largesample of OCD participants to determine whether a reduced item pool would be more efficient incapturing the beliefs underlying OCD. This study also explores whether a smaller number ofdimensions are relevant for assessing the beliefs, interpretations and other cognitive constructsassociated with OC symptoms. The psychometric properties of empirically based, rather thantheoretically derived, subscales are examined using the multi-site data set described in the Part 1paper that includes non-OCD clinical and non-clinical samples.

Method

The methodology employed for this paper is summarized below. A complete description isavailable elsewhere (OCCWG, 2003).

Participants

Subjects were recruited from OCCWG member sites located in Australia, Canada, France,Greece, the Netherlands, Italy, and the United States. Methods regarding translation aredescribed elsewhere (OCCWG, 2001). Because preliminary analyses using Box’s M test indicatedthat the variance–covariance matrices for the OBQ and III sufficiently differed across sampleswith different languages, it was inappropriate to pool these data. The present paper represents theresults from the English-language version of the two measures and constitutes 56% of thecollected data.

The English-language scales were completed by four participant groups: (1) those with a DSM-IV diagnosis of OCD as their most severe problem OC (n ¼ 410), (2) AC (n ¼ 105), (3) CC(n ¼ 87), and (4) SC (n ¼ 291). The OCD sample included 248 participants from Part 1 of thisstudy and an additional sample of 162 participants from OCCWG and other sites who wereincluded in factor analyses. Like participants in Part 1, the additional OCD subjects werediagnosed using standardized interviews and did not differ significantly from the original subjects

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on demographic characteristics (mean age ¼ 36.5 years, 42% male, 52% single; all Fs andw2o1.0).

ACs had one or more of the following diagnoses and did not meet criteria for OCD: panicdisorder (72%), agoraphobia (58%), posttraumatic stress disorder (25%), generalized anxietydisorder (17%), specific phobia (16%), social phobia (13%), and hypochondriasis (2%).(Percentages do not add up to 100 because patients could have more than one disorder.) OCsand ACs were excluded if they had current psychotic or substance use disorders. DSM-IVdiagnoses (American Psychiatric Association, 2000) for clinical participants were established viathe Structured Clinical Interview for DSM-IV (First, Spitzer, Gibbon, & Williams, 1996) for 44%,the Anxiety Disorders Interview Schedule for DSM-IV (Brown, DiNardo, & Barlow, 1994) for47%, and unstructured interview by an experienced clinician for 9%. CCs included friends orfamily of OCCWG members as well as teachers and community service organization members.SCs were primarily first year university or college students most of whom received course creditfor participating in the study.

Demographic information regarding subject groups is available in Part 1 of this study(OCCWG, 2003). Clinical participants (OC and AC, mean age of 35 years) and CC (mean ¼ 42years) were older than student participants (mean age ¼ 21 years). The OC group had more men(44%) than the other samples (32–33% men) and more unmarried participants (52%) than AC orCC subjects (34% and 25% single, respectively). The CC group was significantly better educatedthan other groups (mean ¼ 17 years), and OC and SC samples (mean of 15 years each) were moreeducated than ACs (14 years). The two clinical samples contained more unemployed or disabilitypayment-assisted participants (14–25%) than community or student samples (0%). No differenceswere evident for ethnicity; most participants (88–94%) were Caucasian.

Procedure

The OC and AC groups were recruited primarily from specialty clinics for anxiety disorders;SCs from college classes, and CCs from workplaces, acquaintances, and community serviceorganizations. Informed consent was obtained for all participants.

Measures

OBQ consists of 87 belief statements considered characteristic of obsessive thinking (OCCWG,1997, 2001). Scale items represent six rationally determined subscales thought to represent the keybelief domains of OCD. The subscales are (1) control of thoughts—14 items, (2) importance ofthoughts—14 items, (3) responsibility—16 items, (4) intolerance of uncertainty—13 items, (5)overestimation of threat—14 items, and (6) perfectionism—16 items. Respondents indicate theirgeneral level of agreement with items on a 7-point rating scale that ranges from (�3) ‘‘disagreevery much’’ to (0) ‘‘neutral’’ to (+3) ‘‘agree very much’’. Item responses were transformed to a1–7 scale, and subscale scores were calculated by summing across their respective items.

Interpretation of Intrusions Inventory (III) is a 31-item scale that assesses immediate appraisalsor interpretations of unwanted, distressing intrusive thoughts, images or impulses (OCCWG,1997, 2001). Instructions provide a definition of unwanted intrusions and illustrative examples.Participants write down two intrusive thoughts, images or impulses that they experienced recently

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and then rate the recency, frequency, and distress associated with these intrusions. Respondentsthen rate 31 statements as they pertain to intrusive thoughts like those recorded on thequestionnaire using a scale from 0 (‘‘I did not believe this idea at all’’) to 100 (‘‘I was completelyconvinced this idea was true’’). Three subscales were scored: (1) importance of thoughts—10items, (2) control of thoughts—11 items, and (3) responsibility—10 items. For data analysis, the100-point scale was transformed to a 10-point scale with scores ranging from 0 to 310. Subscalescores were calculated by summing across their respective items.

For the purpose of the analyses in the present study, participants at most sites completedadditional scales including the Padua Inventory (Washington State University revision, PI-R;Burns, Keortge, Formea, & Sternberger, 1996), Beck Anxiety Inventory (BAI, Beck & Steer,1993a), and Beck Depression Inventory (BDI, Beck & Steer, 1993b). Additional measures of OCsymptoms and worry completed in a subset of sites (see OCCWG, 2001, 2003) were not includedin the present study because they were not administered to a sufficiently large number of researchsites or participants.

Results

Factor analyses

Given the elevated inter-correlations among the rationally derived subscales of the OBQ andIII, we sought to determine whether more distinct empirically derived dimensions might underliethe OBQ and III. A priori, it was unclear how the scales might be combined into a parsimoniousset of underlying dimensions. The high subscale intercorrelations indicated that it was unlikelythat each subscale would correspond to a distinct factor. In the absence of alternative, previouslydefined factor models, we conducted exploratory rather than confirmatory factor analyses. Anexploratory factor analysis was conducted separately on the OBQ and III items. Principal axisfactor analysis with oblique rotation was conducted on OBQ items2 for OCD participants only(n ¼ 410 after listwise deletion). The Kaiser–Meyer–Olkin index of sampling adequacy was .95,indicating that the correlation matrix was suitable for factor analysis (Tabachnick & Fidell, 1996).To determine the optimal number of factors to retain in the analysis, the scree plot, theinterpretability of the factor loadings, and the internal stability of each factor according toKaiser’s coefficient alpha of generalizability (Kline & Barrett, 1983) were utilized. These criteriasuggested a 3-factor solution that accounted for 42% of the variance.3 Eigenvalues for the first 5factors were 26.4, 5.4, 4.3, 3.4 and 2.6. The correlations among factors were as follows: Factors 1and 2 (.52), Factors 1 and 3 (.49), and Factors 2 and 3 (.42).

To assess the robustness (replicability) of the factor structure and content, we also conductedfactor analyses of two randomly split samples of n ¼ 205 OCs each. This method yielded virtuallyidentical 3-factor solutions with almost complete overlap in high loading items and similarintercorrelations among factors. Factor analyses conducted with the student sample (the only

2Because the wording of item 71 was nearly identical to that for item 23, by the flip of a coin, item 71 was omitted for

factor analyses which were conducted on 86 items.3Findings available from the corresponding author.

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sample large enough to permit a separate analysis) also produced a 3-factor solution, and again,items loading high on factors in the student sample overlapped closely with those identified for theOC sample. This was especially evident for Factors 2 and 3; Factor 1 included a few perfectionismand certainty items that loaded on Factor 2 in the OCD sample. Overall, the factor structureappeared to be consistent across samples.

Items with factor loadings of .50 or higher (corresponding to ‘‘large’’ loadings; Cohen, 1988)were retained to generate subscales. This relatively high criterion was chosen because nearly allOBQ items loaded above .35 on a factor so that including additional items defeated our aim toreduce the length of the instrument. In addition, including items with lower loadings (e.g., .40–.49)did not alter the basic content of the scales.

The first scale was labelled Responsibility/Threat Estimation and included seven threat items,eight responsibility items and one uncertainty item from the original theoretically derived scales.The 16 items on this factor dealt with preventing harm from happening to oneself or others, theconsequences of inaction, and responsibility for bad things happening. Examples of high loadingitems are: ‘‘Harmful events will happen unless I am very careful’’, ‘‘Avoiding serious problems(for example, illness or accidents) requires constant effort on my part’’, and ‘‘For me, notpreventing harm is as bad as causing harm’’.

The second scale was labelled Perfectionism/Certainty and included 12 perfectionism and fouruncertainty items from the original theoretical scales. These 16 items reflected high, absolutestandards of completion, rigidity, concern over mistakes and feelings of uncertainty. High loadingitems are ‘‘For me, things are not right if they are not perfect’’, and ‘‘If I can’t do somethingperfectly, I shouldn’t do it at all’’, and ‘‘I must be certain of my decisions’’.

The third scale labelled Importance/Control of Thoughts included nine importance of thoughtsand three control of thoughts items from the original theoretically derived scales. These 12 itemsconcerned the consequences of having intrusive and/or distressing thoughts or images,thought–action fusion, and the need to rid oneself of intrusive thoughts. Sample items included‘‘Having a bad thought is morally no different than doing a bad deed’’, ‘‘Having bad thoughtsmeans I am weird or abnormal’’ and ‘‘Having intrusive thoughts means I’m out of control’’.Factor scores were moderately inter-correlated (r’s ranged from .42–.52).

A Principal Axis Factor Analysis (with oblique rotation) based on the total OCsample (N ¼ 410) was performed on all 31 items of the III. The Kaiser–Meyer–Olkin index ofsampling adequacy was again high (.96). All items loaded 4.47 on a single factor whichaccounted for 44% of the variance. Eigenvalues for the first five factors were 11.5, 2.5, 1.8, 1.2 and1.1. Because of the consistently high loadings, we decided to retain all 31 items rather than shortenthe scale. As was done with the OBQ, additional analyses on the randomly split sample of OCparticipants and of SC also produced a single factor with all items loading 4.45 in both OCsamples, and 4.49 in the student sample except for 2 items with factor loadings of .36 and .39. Inview of the consistency of these findings, retention of all 31 items as a single scale was deemedappropriate.

Table 1 presents the zero-order correlations among the three OBQ factor analytically derivedsubscales and the III for the OC and the combined non-OCD samples. The three OBQ subscaleswere moderately correlated in OCD samples (r’s ¼ :422:57), and had higher correlations in thenon-OCD sample (r’s ¼ :642:72). The OBQ subscales correlated moderately highly with the IIItotal score (r’s ¼ :352:63) in OCD and non-OCD samples.

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Table 1

Correlations among the empirically derived OBQ (44-items) subscales and the III (31-items)

Empirically derived OBQ scales OBQ-44 Total RT PC ICT III-Total

OBQ-44 total — .88 .83 .76 .59

Responsibility/threat estimation (RT) .91 — .57 .55 .55

Perfectionism/certainty (PC) .91 .73 — .42 .35

Importance/control of thoughts (ICT) .83 .67 .63 — .60

III total score .66 .63 .54 .60 —

OBQ ¼ Obsessive Beliefs Questionnaire, RT ¼ Responsibility/Threat Estimation, PC ¼ Perfectionism/Certainty,

ICT ¼ Importance/Control of Thoughts, III ¼ Interpretation of Intrusions Inventory. Correlations above the diagonal

are for OC participants (n ¼ 244 after listwise deletion). Correlations below the diagonal are for the combined anxious,

community and student control samples (n ¼ 469 after listwise deletion). All correlations are significant at po:001.

Obsessive Compulsive Cognitions Working Group / Behaviour Research and Therapy 43 (2005) 1527–1542 1533

Internal consistency

The internal consistency coefficients (Cronbach a) for all three OBQ subscales were high andcomparable to those reported for the rationally derived subscales (OCCWG, 2003). Figures forthe OCD sample were .93 for Responsibility/Threat Estimation and Perfectionism/Certainty; .89for Importance/Control of Thoughts; .95 for OBQ Total score. Internal consistency for the IIItotal score was also high (.94). Coefficients a for these scales were comparable for men and womenand for the OCD (n ¼ 248) and non-OCD (n ¼ 483) samples. According to 2 (gender)� 2(OCD/non-OCD) ANOVAs, no effect of gender was observed (all p’s4.30) nor interaction of gender byOCD status (p’s4.13) for OBQ total and subscale scores and for the III. In summary, the resultssupport the internal consistence form of reliability of the OBQ and III scales.

Group comparisons

Table 2 presents the means, standard deviations, F values and the results of post hoccomparisons for the four samples on the three OBQ subscales. A one-way MANOVA performedon the three OBQ subscales was highly significant; Pillai F ð3332Þ ¼ 588:91, po.001). One-wayANOVAs conducted for each subscale revealed significant group differences on all three OBQscales. Post hoc comparisons (Table 2) indicated that the OC group scored significantly higherthan the non-OCD anxious patients on OBQ Responsibility/Threat Estimation and onImportance/Control of Thoughts, but not on the Perfectionism/Certainty subscale. On allcomparisons, anxious patients scored significantly higher than students who scored higher thanCC. Overall, group differences on the empirically derived scales were very similar to resultsobtained with the rationally determined subscales in which Perfectionism and Tolerance forUncertainty did not significantly distinguish OC samples from AC. Findings from a one-wayANOVA comparing groups on the III total score were significant, F ð3638Þ ¼ 97:28, po.001. Posthoc comparisons indicated that the OC group scored significantly higher than all other groups. Tosummarize, the results generally support the criterion-related (known groups) validity of the OBQand III subscales.

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Table 2

Criterion-related (known-groups) validity: Comparisons of group means on the OBQ-44 total score and subscales

Obsessive-compulsive

disorder (OC) n ¼ 244

Anxious

controls (AC)

n ¼ 103

Student

controls (SC)

n ¼ 284

Community

controls (CC)

n ¼ 86

F df Significant SNK

post-hoc comparisons

(po .05)

M SD M SD M SD M SD

OBQ-44 total 174.3 50.2 159.3 53.0 131.3 44.3 96.0 35.1 74.72*** 3713 OC4AC4SC4CC

Responsibility/threat 64.5 22.4 59.8 22.8 48.4 18.7 34.2 13.0 60.36*** 3713 OC4AC4SC4CC

Perfectionism/certain 69.9 22.1 65.7 21.7 55.5 20.1 41.4 18.1 48.26*** 3713 OC, AC4SC4CC

Import./control of Thgt 39.8 16.3 33.9 15.8 27.1 11.6 20.5 9.3 59.13*** 3713 OC4AC4SC4CC

III-31 total score 1599.3 670.0 1365.1 789.8 720.6 569.5 514.6 454.3 100.79*** 3628 OC4AC4SC4CC

OBQ ¼ Obsessive Beliefs Questionnaire, ***po.001.

Obsessive

Com

pulsive

Cog

nitio

ns

Work

ing

Gro

up

/B

ehaviou

rR

esearch

and

Thera

py

43

(2005)

1527

–1542

1534

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Correlations with measures of OC symptoms

Convergent validity was tested by computing correlations between the OBQ and III with themeasures of OC symptoms for the OC sample (n ¼ 186 after listwise deletion). Table 3 shows thecorrelations, most of which were significant. Correlations were based on the OC sample becausethis was the largest of the samples completing the measures in the table. Inclusion of the other,smaller samples induces a confound between sample size and statistical significance; a smallcorrelation based on a large sample may be statistically significant because of high statisticalpower, whereas a large correlation based on a smaller sample may not be significant because oflower power. The results in Table 3 support the convergent validity of the empirically derivedOBQ and III.

Regression analyses

Hierarchical regression analyses, again using the OC sample, provided a stringent test of thecognitive measures’ capacity to predict specific types of OC symptoms after controlling for generaldistress (as indexed by the BDI and BAI). Accordingly, these analyses were used as tests ofdiscriminant validity. PI-R subscales served as the dependent variables because these representseveral different manifestations of OC symptoms (harming, checking, contamination, grooming).The BDI and BAI were simultaneously entered in step 1 as a block, followed in step 2 by the 3OBQ subscales simultaneously entered as a block (n ¼ 179) or by the III total score (n ¼ 167).(The OBQ and III were examined in separate regressions.) Tolerance values were well withinacceptable limits, indicating that multicollinearity was not a problem. Beta weights andsignificance levels are presented in Table 4. The results indicate that all but one of the cognitivemeasures predicted at least some types of OC symptoms represented on the Padua Inventory.After controlling for general distress, OBQ Responsibility/Threat Estimation predicted Harming

Table 3

Convergent validity: Correlations with scales from the Revised Padua Inventory (PI-R)

PI-R harm

impulses

PI-R harm

thoughts

PI-R

grooming

PI-R

checking

PI-R

contamination

OBQ-44 total .27**** .59**** .31**** .37**** .29****

Responsibility/threat .22*** .62**** .19** .27**** .31****

Perfectionism/certainty .19** .39**** .43**** .45**** .27****

Importance/control of

thoughts

.27**** .42**** .10 .14 .10

III-31 total score .20** .43**** .09 .19** .11

*po.05, **po.01, ***po.005, ****po.001.

OBQ ¼ Obsessive Beliefs Questionnaire, RT ¼ Responsibility/Threat Estimation, PC ¼ Perfectionism/Certainty,

ICT ¼ Importance/Control of Thoughts, III ¼ Interpretation of Intrusions Inventory, PI-R ¼ padua inventory-

revised, Harm impulses ¼ impulses to harm self or others, Harm thoughts ¼ thoughts of harm to self or others,

Groom ¼ dressing and grooming. Based on OC sample (n ¼ 186 after listwise deletion).

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Table 4

Discriminant validity: Beta weights from hierarchical regressions examining the association of cognitive measures with

OC symptoms, controlling for general distress (general anxiety and depression)

Predictor PI-R harm impulses PI-R harm thoughts PI-R grooming PI-R checking PI-R contamination

Regressions for OBQ subscales:

BDI �.08 .05 �.04 �.07 .12

BAI .35*** .20** .10 .11 .04

OBQ–RT .02 .46**** �.04 .06 .23*

OBQ–PC .06 �.01 .48**** .45**** .12

OBQ–ICT .11 .09 �.07 �.09 �.13

Regressions for III total score:

BDI �.05 .14 .15 .11 .22*

BAI .37**** .28**** .12 .12 .07

III .09 .30**** .00 .12 .01

*po.05, **po.01, ***po.005, ****po.001.

OBQ ¼ Obsessive Beliefs Questionnaire, RT ¼ Responsibility/Threat Estimation, PC ¼ Perfectionism/Certainty,

ICT ¼ Importance/Control of Thoughts, III ¼ Interpretation of Intrusions Inventory, PI-R ¼ padua inventory-

revised, Harm impulses ¼ impulses to harm self or others, Harm thoughts ¼ thoughts of harm to self or others,

Groom ¼ dressing and grooming, BDI ¼ Beck Depression Inventory, BAI ¼ Beck Anxiety Inventory. Based on the

OC sample (n ¼ 179 for OBQ analyses and 167 for III analyses, after listwise deletion).

Obsessive Compulsive Cognitions Working Group / Behaviour Research and Therapy 43 (2005) 1527–15421536

thoughts and Contamination subscales of the PI-R, whereas the Perfectionism/Certainty subscalepredicted the PI-R Grooming and Checking scales. The OBQ Importance/Control of Thoughtssubscale did not predict any PI-R scale, but in contrast, the III total score predicted Harmingthoughts. Comparable regression analyses using the original subscales of the Padua Inventory(Sanavio, 1988) as the dependent variable provided very similar results; again, the Importance/Control of Thoughts scale did not predict any Padua scale. In sum, the results of Table 4 providesome support for the discriminant validity of the OBQ and III.

Discussion

The present study sought to determine whether factor analyses of the 87-item OBQ and 31-itemIII would permit reduction of the number of items, particularly for the OBQ which is quitelengthy for use in clinical settings. We also sought to reduce overlap among factors evident in highcorrelations among subscales in our previous study (OCCWG, 2003). Three factors emerged forthe OBQ, and inclusion of high loading items yielded a 44-item total scale with three subscales ofapproximately similar length. Subscales were labelled Responsibility/Threat Estimation,Perfectionism/Certainty, and Importance/Control of Thoughts. Subscales had high internalconsistency. The intercorrelations among subscales in the OCD sample (r’s ¼ :422:57) appearedto improve somewhat on those from the original theoretically derived subscales (r’s ¼ :502:79).

The combined factors derived from the factor analysis are intuitively understandable. Thatresponsibility and danger items loaded on the same factor is consistent with the assumption in

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cognitive theories about OCD that excessive concerns about responsibility lead to obsessionsabout causing or preventing harm (Rachman, 1997; Salkovskis, 1985, 1989). The overlap ofperfectionism and the need for certainty is consistent with the clinical observation that OCDpatients typically try to minimize mistakes or errors in their efforts to dispel doubts provoked byintrusive thoughts. In our earlier studies of the OBQ in OC samples (OCCWG, 2001, 2003),Perfectionism and Certainty subscales were highly correlated, although need for certainty was alsoclosely related to threat estimation as might be expected. It also makes sense that beliefs aboutoverimportance and control of thoughts loaded on the same factor. Overimportance given tointrusive thoughts commonly leads OC patients to try to control these thoughts via suppression,rethinking and a variety of other strategies designed to remove the thoughts (Freeston &Ladouceur, 1997).

In factor analytic findings for the III a single factor emerged, indicting that its theoreticallyderived subscales are not meaningfully differentiated empirically. That is, items written to capturehypothesized domains of importance and control of thoughts and responsibility loaded togetheron a single factor that can be described as negative interpretation of intrusive thoughts. As in Part1 of this study, the III total score correlated moderately highly with OBQ subscales (r’s ¼ :352:60for OCs and .54–.63 for non-OCs), suggesting that the distinction between appraisals/interpretations of thoughts and beliefs may also be difficult for many people to make. Perhapsthese psychological distinctions postulated by theorists in cognitive models of OCD (Freeston etal., 1996; Rachman, 1997; Salkovskis, 1985, 1989) may not be detectable with self-reportquestionnaire methods. Because the rational evaluation of interpretations and of beliefs is abackbone of cognitive therapy for OCD (and for other disorders), this issue merits further study.

Although the empirically derived subscales of the OBQ do not substantially improve uponconvergent or discriminant validity compared to the theoretically based scales, they are at leastcomparable and all means are in the predicted direction for the shorter instrument. All threesubscales displayed good known-groups validity in distinguishing OC patients from non-clinicalcontrols. OC patients’ scores on OBQ subscales were somewhat higher than those of anxietydisordered control patients. This difference was significant for all but the Perfectionism/Uncertainty scale, a finding also reported for the original perfectionism and uncertainty subscalesof the OBQ-87. This finding is not surprising in view of strong perfectionistic tendencies identifiedin a number of other disorders (e.g., body dysmorphic disorder or eating disorders; Shafran, 2002;Wilhelm & Neziroglu, 2002). Findings indicated good convergent validity and promising, butsomewhat weaker discriminant validity. For the latter, regression analyses controlling for generaldistress revealed that the OBQ and III generally predicted OC symptom subtypes in patterns thatmight be expected clinically. This finding is consistent with theoretical postulations (e.g.,Rachman, 2002) that certain types of negative interpretations and beliefs associated with intrusivethoughts foster particular OC symptoms, although considerable additional evidence will berequired for conclusions about causality.

That Responsibility/Threat Estimation was most strongly linked to harming thoughts and tocontamination/washing symptoms accords with theoretical thinking about these obsessivesymptoms (Rachman, 1997, 1998; Salkovskis, 1985) and with our previous findings of a strongrelationship of threat estimation to contamination obsessions and washing compulsions(OCCWG, 2001). Likewise, the association of Perfectionism/Certainty with grooming/dressingsymptoms that typically include symmetry concerns and with checking aimed at achieving

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certainty makes theoretical and clinical sense. Surprisingly, although the III, which identifiescognitive reactions to intrusive thoughts, predicted harming thoughts, this was not true for theOBQ beliefs about Importance and Control of Thoughts, as we expected. Reasons for thisdiscrepancy are not apparent since research findings suggest that over-estimation of theimportance and need to control thoughts often occurs in response to ideas of harming (Purdon &Clark, 2002; Thordarson & Shafran, 2002). In any case, although the regression analyses indicatethat OBQ-44 subscales cannot be considered to assess beliefs that pertain only to obsessivethoughts, 2 of the 3 scales predicted obsessive symptoms independent of general distress. This isimpressive because the general distress is likely caused, at least in part, by the OC symptomsthemselves. Thus, these results, especially for the OBQ responsibility and perfectionism scales,provide fairly strong evidence for a specific link between beliefs and symptoms (Appendix A).

There is probably little advantage in using the 6 OBQ-87 subscales or the 3 III subscales,particularly given their multicollinearity which will make interpretation of findings unreliable.Further, the use of a greater number of subscales may give the misleading impression of amultidimensional construct when in reality several belief domains appear to be more similar thandifferent. Thus, the 44-item OBQ with its 3 subscales has advantages over the 87-item version.However, retention of more subscales may be useful when investigators wish to examine thespecific content of one or more of the hypothesized domains contained in the OBQ (e.g.,importance of thoughts), comparing it to related constructs (e.g., controlling thoughts). Further,hypothesized domains may yet prove relevant to specific manifestations of OC symptoms (e.g.,washing, checking) or to development of cognitive interventions for OCD.

The domains included in OBQ were not intended to include all content areas that are relevantor specific to OCD. Nor does the present study address whether the belief domains assessed in theOBQ provide greater explanatory power for OC symptoms compared to more general measuresof beliefs (e.g., Dysfunctional Attitude Scale; Weissman, 1980) intended to assess depressivecognitions. We encourage further research into other areas of cognitive content (e.g., fear ofpositive experiences, sensitivity to discomfort, causal inference) that may elucidate further thenature of obsessional thinking and ritualistic acts.

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Appendix A. Obsessional beliefs questionnaire (OBQ-44)

This inventory lists different attitudes or beliefs that people sometimes hold. Read each statement carefully and decidehow much you agree or disagree with it.

For each of the statements, choose the number matching the answer that best describes how you think. Because peopleare different, there are no right or wrong answers.

To decide whether a given statement is typical of your way of looking at things, simply keep in mind what you are likemost of the time.

Use the following scale:

1 2 3 4 5 6 7

Disagreevery much

Disagree moderately Agree alittle

Neither agreenor disagree

Agree alittle

Agreemoderately

Agree very much

In making your ratings, try to avoid using the middle point of the scale (4), but rather indicate whether you usually disagree or agreewith the statements about your own beliefs and attitudes.

RT 1. I often think things around me are unsafe. 1 2 3 4 5 6 7PC 2. If I’m not absolutely sure of something, I’m bound to make a mistake. 1 2 3 4 5 6 7PC 3. Things should be perfect according to my own standards. 1 2 3 4 5 6 7PC 4. In order to be a worthwhile person, I must be perfect at everything I do. 1 2 3 4 5 6 7RT 5. When I see any opportunity to do so, I must act to prevent bad things from

happening.RT 6. Even if harm is very unlikely, I should try to prevent it at any cost. 1 2 3 4 5 6 7ICT 7. For me, having bad urges is as bad as actually carrying them out. 1 2 3 4 5 6 7RT 8. If I don’t act when I foresee danger, then I am to blame for any consequences 1 2 3 4 5 6 7PC 9. If I can’t do something perfectly, I shouldn’t do it at all. 1 2 3 4 5 6 7PC 10. I must work to my full potential at all times. 1 2 3 4 5 6 7PC 11. It is essential for me to consider all possible outcomes of a situation. 1 2 3 4 5 6 7PC 12. Even minor mistakes mean a job is not complete. 1 2 3 4 5 6 7ICT 13. If I have aggressive thoughts or impulses about my loved ones, this means I may

secretly want to hurt them.1 2 3 4 5 6 7

PC 14. I must be certain of my decisions. 1 2 3 4 5 6 7RT 15. In all kinds of daily situations, failing to prevent harm is just as bad as deliberately

causing harm1 2 3 4 5 6 7

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SRT 16. Avoiding serious problems (for example, illness or accidents) requires constant

effort on my part.1 2 3 4 5 6 7

RT 17. For me, not preventing harm is as bad as causing harm. 1 2 3 4 5 6 7PC 18. I should be upset if I make a mistake. 1 2 3 4 5 6 7RT 19. I should make sure others are protected from any negative consequences of my

decisions or actions1 2 3 4 5 6 7

PC 20. For me, things are not right if they are not perfect. 1 2 3 4 5 6 7ICT 21. Having nasty thoughts means I am a terrible person. 1 2 3 4 5 6 7RT 22. If I do not take extra precautions, I am more likely than others to have or cause a

serious disaster.1 2 3 4 5 6 7

RT 23. In order to feel safe, I have to be as prepared as possible for anything that could gowrong.

1 2 3 4 5 6 7

ICT 24. I should not have bizarre or disgusting thoughts. 1 2 3 4 5 6 7PC 25. For me, making a mistake is as bad as failing completely. 1 2 3 4 5 6 7PC 26. It is essential for everything to be clear cut, even in minor matters. 1 2 3 4 5 6 7ICT 27. Having a blasphemous thought is as sinful as committing a sacrilegious act. 1 2 3 4 5 6 7ICT 28. I should be able to rid my mind of unwanted thoughts. 1 2 3 4 5 6 7RT 29. I am more likely than other people to accidentally cause harm to myself or to others. 1 2 3 4 5 6 7ICT 30. Having bad thoughts means I am weird or abnormal. 1 2 3 4 5 6 7PC 31. I must be the best at things that are important to me. 1 2 3 4 5 6 7ICT 32. Having an unwanted sexual thought or image means I really want to do it. 1 2 3 4 5 6 7RT 33. If my actions could have even a small effect on a potential misfortune, I am

responsible for the outcome.1 2 3 4 5 6 7

RT 34. Even when I am careful, I often think that bad things will happen. 1 2 3 4 5 6 7ICT 35. Having intrusive thoughts means I’m out of control. 1 2 3 4 5 6 7RT 36. Harmful events will happen unless I am very careful. 1 2 3 4 5 6 7PC 37. I must keep working at something until it’s done exactly right. 1 2 3 4 5 6 7ICT 38. Having violent thoughts means I will lose control and become violent. 1 2 3 4 5 6 7RT 39. To me, failing to prevent a disaster is as bad as causing it. 1 2 3 4 5 6 7PC 40. If I don’t do a job perfectly, people won’t respect me. 1 2 3 4 5 6 7RT 41. Even ordinary experiences in my life are full of risk. 1 2 3 4 5 6 7ICT 42. Having a bad thought is morally no different than doing a bad deed. 1 2 3 4 5 6 7PC 43. No matter what I do, it won’t be good enough. 1 2 3 4 5 6 7ICT 44. If I don’t control my thoughts, I’ll be punished. 1 2 3 4 5 6 7

RT ¼ Responsibility/Threat estimation.

PC ¼ Perfectionism/Certainty.

ICT ¼ Importance/Control of Thoughts.

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