IUS %26 BDI Description

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A psychometric analysis of the Intolerance ofUncertainty Scale among four racial groups

Peter J. Norton*

Department of Psychology, University of Houston, 126 Heyne Building,

Houston, TX 77204-502, USA

Received 19 May 2004; received in revised form 3 August 2004; accepted 16 August 2004

Abstract

Recent psychometric analyses examining the cross-cultural validity of key anxietymeasures have suggested that some, such as the Anxiety Sensitivity Index (ASI), may hold

different psychometric characteristics among different racial or national groups. The

Intolerance of Uncertainty Scale (IUS) is a self-report measure that, like the ASI, appears

to assess a predispositional risk for developing some anxiety and mood disorders. Despite

its validation in both a French and English version, the majority of the research conducted

on the IUS has used predominantly Caucasian samples. Given this, the purpose of this

research was to examine and compare the psychometric properties of the IUS among non-

clinical participants of four racial groups: African American, Caucasian, Hispanic/Latino,

and Southeast Asian. The data suggested generally strong, and highly similar, estimates of

reliability and validity across the four racial groups. The factor structure of the IUS,

however, was poorly interpretable among any of the groups. Implications for use of the IUS

with different racial groups are discussed.

# 2004 Elsevier Inc. All rights reserved.

Keywords: Psychometric analyses; Intolerance of uncertainty scale; Cross-cultural assessment

The increasing awareness of multicultural issues in modern psychology has led

to a burgeoning recognition that psychometric characteristics of our research andclinical assessment tools must be examined within a multicultural context.

Indeed, recent analyses have suggested that some commonly used may function

Anxiety Disorders

19 (2005) 699707

* Tel.: +1 713 743 8675; fax: +1 713 743 8633.

E-mail address: [email protected].

0887-6185/$ see front matter # 2004 Elsevier Inc. All rights reserved.

doi:10.1016/j.janxdis.2004.08.002


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differently among different groups. The Anxiety Sensitivity Index (ASI; Peterson

& Reiss, 1992), for example, is a measure for which the psychometric

characteristics have been extensively evaluated. However, recent psychometric

evaluations of the ASI among individuals of different racial groups (e.g.,Carter,

Miller, Sbrocco, Suchday, & Lewis, 1999; Norton, De Coteau, Hope, & Anderson,

2004; Zvolensky, McNeil, Porter, & Stewart, 2001) and nationalities (e.g.,

Zvolensky et al., 2003) have generally suggested that the psychometric

characteristics of the ASI vary considerably among various groups. These data

underscore the need to evaluate cross-cultural applicability of assessment

measures. Indeed, asMalgady (1996)articulates, perhaps the emphasis in cross-

cultural research should be on assuming differences until proven otherwise, as

opposed to our traditional approach of assuming the null until rejected.

Recent etiological models of anxiety and depression have suggested that

anxiety sensitivity, the construct measured by the ASI, may act as a semi-specific

risk factor for the development of panic disorder and hypochondriasis above-and-

beyond the elevated general risk attributable to neuroticism (Norton, Sexton,

Walker, & Norton, unpublished manuscript;Sexton, Norton, Walker, & Norton,

2003). These same studies suggested that another construct, intolerance of

uncertainty, may also be a semi-specific risk for generalized anxiety and worry

beyond the general non-specific risk attributable to neuroticism. Intolerance of

uncertainty is characterized by a tendency to perceive ambiguous situations as

threatening and, consequently, uncertainty is a source of fear or discomfort which

contributes to the development of generalized anxiety and worry (Dugas, Gagnon,

Ladouceur, & Freeston, 1998;Freeston, Rheaume, Letarte, Dugas, & Ladouceur,

1994; Lachance, Ladouceur, & Dugas, 1999; Ladouceur, Gosselin, & Dugas,

2000a,b). To assess this intolerance of uncertainty construct, Freeston et al. (1994)

developed the Intolerance of Uncertainty Scale (IUS), a self-report measure

designed to measure this construct.

Initial examinations of the psychometric characteristics of the IUS have been

supportive of the measure. Freeston et al. (1994) reported a student sample mean of

43.8 (S.D. = 10.8). Their analyses suggested excellent internal consistency (a = .91)

and 5-week test-retest reliability (r = .74). Validity was demonstrated with

correlations with measures of worry beyond that accounted for by measures of

anxiety and depression. Exploratory factor analysis suggested a five-factor structure,

with factors described as (1) beliefs that uncertainty is unacceptable and should be

avoided, (2) being uncertain reflects badly on a person, (3) uncertainty results in

stress, (4) uncertainty results in frustration, and (5) uncertainty prevents action.

Buhr and Dugas (2002)evaluated an English language version of the IUS and

found comparable results. They reported a student sample mean of 54.78 (S.D. =

17.44), excellent internal consistency (a = .94), and strong 5-week test-retest

reliability (r= .74). As with Freeston et al. (1994), validity was supported by

correlations with measures of worry and anxiety, and the prediction of worry

above-and-beyond measures of anxiety and depression. Unlike Freeston et al.,

however, Buhr and Dugas (2002) found stronger support for as four factor

P.J. Norton / Anxiety Disorders 19 (2005) 699707700


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structure. They defined their factors as (1) uncertainty leads to the inability to act,

(2) uncertainty is stressful and upsetting, (3) unexpected events are negative and

should be avoided, and (4) being uncertain about the future is unfair.

These reliability and validity data, while impressive, were derived from

predominantly Caucasian samples (Buhr & Dugas, 2002;Freeston et al., 1994).

Therefore, in order to continue the cross-cultural examination of key

psychometric measures, this study examines the characteristics of the Intolerance

of Uncertainty Scale (IUS; Buhr & Dugas, 2002;Freeston, Rheaume, Letarte,

Dugas, & Ladouceur, 1994) across a sample of participants of African, Caucasian,

Hispanic, and Southeast Asian decent.

1. Methods

1.1. Participants and procedures

Five-hundred and forty undergraduate students from the University of Houston

consented to participate in a large questionnaire-based study. Participants were

either tested en masse in a large classroom setting or were allowed to complete

questionnaires on their own time and return them within 1 week. Of the total

sample, 93 identified themselves as African American/Black (non-Hispanic),

149 asCaucasian/White (non-Hispanic),113 asHispanic/Latino(a),and 94

asSoutheast Asian.Only participants of these four racial groups were included

in the current study, and individuals who identified themselves as Multiracial

were not included. As an admission requirement to the University of Houston, all

students must have passed required high school English coursework or performed

satisfactorily on the Test of English and a Foreign Language (TOEFL). Of these

participants, 310 (69.0%) were women, 135 (30.1%) were men, and 4 (0.9%) did

not report their sex. Participants ranged in age from 17 to 51 years of age (M=

21.65, S.D. = 4.93), and represented all years of undergraduate study (32.7%

Freshman, 22.7% Sophomore; 23.4% Junior, 20.9% Senior or Post-Baccalaure-

ate; 0.2% missing data).

1.2. Measures

As part of a larger study, participants completed a demographics form and a

large battery of self-report questionnaires. For the purposes of this study, data

from the IUS, Generalized Anxiety Disorder Questionnaire-IV, Penn State Worry

Questionnaire, Beck Anxiety Inventory, and Beck Depression Inventory were

examined.

1.2.1. Intolerance of Uncertainty Scale (IUS)

The Intolerance of Uncertainty Scale (Buhr & Dugas, 2002;Freeston et al.,

1994) contains 27 items assessingemotional, cognitive and behavioral reactions

P.J. Norton / Anxiety Disorders 19 (2005) 699707 701


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to ambiguous situations, implications of being uncertain, and attempts to control

the future (Dugas et al., 1994; p. 596). Items are scored on a 1 ( not at all

characteristic of me) t o 5 (entirely characteristic of me) Likert-type scales,

yielding possible scores from 27 to 135. Despite the reported multifactor

structures, the IUS is most commonly summed as a total scale score (Antony,

Orsillo, & Roemer, 2001).

1.2.2. Generalized Anxiety Disorder Questionnaire-IV (GADQ-IV;Newman et

al., 2002)

The GADQ-IV, a revision of the GAD-Q (Roemer, Borkovec, Posa, &

Borkovec, 1995) is a 9-item self-report questionnaire that assesses generalized

anxiety disorder criteria. It specifically assesses the presence of excessive worry

and its uncontrollability, number of excessive worry topics, associated symptoms,

and the interference and distress associated with the worry. The GADQ-IV has

shown excellent diagnostic sensitivity and specificity, as well as good test-retest

reliability and both convergent and discriminant validity (Newman et al., 2002).

1.2.3. Penn State Worry Questionnaire (PSWQ;Meyer, Metzger, & Borkovec,

1990)

The PSWQ is a 16-item self-report measure of the frequency and intensity of

worry, the principal characteristic of generalized anxiety disorder. The PSWQ has

repeatedly demonstrated strong psychometric properties in clinical and non-

clinical samples (Meyer et al., 1990).

1.2.4. Beck Anxiety Inventory (BAI)

The BAI is a 21-item self-report measure designed as a general measure of

anxiety symptom severity (Beck, Epstein, Brown, & Steer, 1988; Beck & Steer,

1990). The BAI has demonstrated good psychometric properties with non-clinical

college populations (seeCreamer, Foran, & Bell, 1995).

1.2.5. Beck Depression Inventory-II (BDI;Beck, Steer, & Brown, 1996)

The BDI is an extensively used 21-item measure of the somatic, cognitive and

affective domains of depression.Dozois, Dobson, and Ahnberg (1998)report that

the BDI possesses good reliability and validity.

2. Results

2.1. Scale summary

Scores on the IUS ranged from 27 to 124, with a mean of 54.88 (S.D. = 18.71).

No significant difference by sex was observed on the total score (men: mean =

53.07, S.D. = 17.21; women: mean = 55.62, S.D. = 19.35), F(1,443) = 1.74,P =

.188. Further, no differences in mean IUS scores were observed across racial



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groups (African American mean = 52.65, S.D. = 20.03; Caucasian mean = 54.15,

S.D. = 17.75; Hispanic mean = 55.45, S.D. = 18.07; Southeast Asian mean =

57.53, S.D. = 19.54), F (3,445) = 1.183, P = .316.

2.2. Internal consistency

Internal consistency of the IUS across the entire sample was very good (a =

.945). Furthermore, alpha coefficients were quite similar across participants of

African (a = .951), Caucasian (a = .942), Hispanic (a = .934), and Southeast

Asian decent (a = .954).

2.3. Factor structure

To be consistent with the analyses and results presented by Buhr and Dugas

(2001), exploratory factor analysis using Principle Factor Analysis and a Promax

rotation was used to identify the probable factor structure. Although a confirmatory

approach might be desirable, the inconsistency between the factors structures

extracted thus far suggests that such methods might be premature. The number of

factors to retain was determined using the Kaiser rule (eigenvalue> 1; Kaiser, 1961),

scree plot examination (Cattell, 1966), and factor structure interpretability.

Using the Kaiser rule, a 5-factor structure was extracted for African American,

Caucasian, and Southeast Asian participants, while a 6-factor solution emerged

with Hispanic participants. Examination of the scree plots suggested 5-factor

solutions were appropriate all four groups. However, the 5-factor solutions

differed greatly from each other (mean Coefficient of Congruence between

respective pairs = 0.20), as well as from those obtained byBuhr and Dugas (2002)

and Freeston et al. (1994). In addition, the factor solutions showed extensive

multi-vocal item loadings (average of five items loading 0.30 or greater on

multiple factors), and poor factor interpretability. GivenBuhr and Dugas (2002)

report of an interpretable 4-factor solution, exploratory factor analyses were

recomputed constraining to four factor solutions. All rotated solutions converged

but, again, the solutions differed greatly from each other (mean Coefficient of

Congruence between respective pairs = 0.21), multi-vocality was widespread, and

factors were poorly interpretability.1

2.4. Convergent validity

IUS was strongly correlated with PSWQ and GADQ-IV for each group

(Table 1). The magnitudes of the correlations were then compared across groups

using the Fisher test of Ztransformed independent-sample correlations. None

of the corresponding correlations differed significantly across racial groups

(all Zs < 1.73).


1 Pattern matrices available from the author upon request.


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The incremental validity of the IUS was next assessed to determine if the IAS

significantly related to measures of worry and generalized anxiety above and

beyond that accounted for by general measures of anxiety and depression. First,

for each racial group, a hierarchical multiple regression, was conducted with

PSWQ as the criterion and BAI and BDI entered in the first step. IUS was then

entered in the second step. As shown inTable 2, the IUS significantly predicted

PSWQ scores beyond that already accounted for by BAI and BDI for each racial

group. Second, identical regressions were conducted for each group, save that

GADQ-IV was the criterion variable. As shown inTable 3, IUS predicted GADQ-

IVabove and beyond BAI and BDI for all groups except participants of Southeast

Asian decent, rpartial = .186, P = .112.

3. Discussion

Malgady (1996)appealed for a reconsideration of established decision-making

rules when conducting cross-cultural mental health research. Most importantly,


Table 1

Pearson correlations between IUS and measures of worry/generalized anxiety

rIUS.PSWQ rIUS.GADQ-IV

African American .661 .687

Caucasian .617 .629

Hispanic .579 .686

Southeast Asian .658 .512

All correlation coefficients significant (P < .001).

Table 2

Step 2 of hierarchical regressions predicting the PSWQRacial group Variable B S.E. B b rPartial P Model r

2

African American BDI 0.152 0.183 0.116 .097 .410 .480

BAI 0.607 0.196 0.390 .342 .003

IUS 0.318 0.078 0.484 .431


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Malgady contends thatincorrect retention [of the null hypothesis] (Type II error

= disservice to minority clients) may be more serious than its incorrect rejection

(Type I error = misdirection to the mental health service system)(1996; p. 73).

Therefore, strong evidence should be required before assuming there are no

differences across groups on assessment or treatment tools. Results presented

here, however, do provide strong evidence of cross-racial uniformity for the IUS.

Scores on the IUS were similarly internally consistent for each of the groups.

Finally, the previously reported (Buhr & Dugas, 2002) zero-order and unique

relationships between IUS and worry/generalized anxiety held consistent across

all groups.

Differences in the factor structures across groups in this study are, on the other

hand, surprising. However, given the factor structure instability previously

reported with different samples (e.g.,Buhr & Dugas, 2002;Freeston et al., 1994),

the structure differences observed here should not automatically be attributed to

cultural or racial variables. Perhaps additional or modified items are necessary to

obtain fuller coverage of theoretically derived factors of the intolerance of

uncertainty construct. Conversely, the factor analysis may have picked up on

irrelevant associations among the 27 items. If so, the very high alpha coefficients

observed here and elsewhere (Buhr & Dugas, 2002; Freeston et al., 1994) suggests

that the removal ofmisbehavingitems would likely not impact scale reliability

substantially. Should the IUS be revised in either way, similar cross-cultural

examination of its factor structure would be warranted. It is also possible that

intolerance of uncertainty is a one-dimensional construct, with the varied factor

structures reflecting idiosyncrasies within each sample.

Several limitations exist within this study that may have influenced the results.

First, although representing a broad range of worry and generalized anxiety, the

sample was recruited from an undergraduate population. Based on prevalence


Table 3

Step 2 of hierarchical regressions predicting the GADQ-IV

Racial group Variable B S.E. B b rPartial P Model r2

African American BDI 0.177 0.092 0.232 .220 .059 .614

BAI 0.299 0.099 0.329 .336 .003

IUS 0.126 0.040 0.328 .351 .002

Caucasian BDI 0.167 0.066 0.214 .215 .013 .593

BAI 0.340 0.072 0.337 .379 .000

IUS 0.158 0.032 0.362 .393 .000

Hispanic/Latino BDI 0.079 0.075 0.110 .114 .295 .570

BAI 0.247 0.078 0.323 .328 .002

IUS 0.169 0.045 0.410 .379 .000

Southeast Asian BDI 0.157 0.212 0.212 .223 .056 .548

BAI 0.443 0.494 0.494 .505 .000

IUS 0.059 0.159 0.159 .186 .112

GADQ-IV: Generalized Anxiety Disorder Questionnaire-IV; BAI: Beck Anxiety Inventory; BDI: Beck

Depression Inventory; IUS: Intolerance of Uncertainty Scale.


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statistics, it can be estimated that a small percentage of the sample would meet

criteria for generalized anxiety disorder. However, it still may be that the general

uniformity of the psychometric estimates may relate to the predominantly non-

clinical nature of the sample. Changes in the range of IUS scores obtained with

clinical samples may lead to changes in the psychometric estimates of the

measure, particularly coefficient alpha. Therefore, replication with clinical

samples representing different racial groups could clarify this issue.

Secondly, this study did not employ any measure of cultural identification or

acculturation. Therefore, the extent to which the participants were representative

of all individuals within these racial groups cannot be determined. A third

limitation is that, as is far too common, individuals of multiracial decent were

excluded from the analyses. Unfortunately, sample sizes for any specific

multiracial profile were too small for analyses, and the extent to which multiracial

participants should be considered a unique group, or a part of one or more racial

groups, is unclear. Inclusion of measures of cultural identification may provide

guidance.

Finally, the simple categorization of participants into racial groups may mask

variations among subpopulations within broader racial groups. For example,

Norton et al. (2004) and Zvolensky et al. (2001) both examined the factor

structure of the Anxiety Sensitivity Index among Native Americans. However,

when participants with a broad range of tribal affiliations were clustered together,

the resulting factor structure was quite different than when examining a single

tribal group. Future studies should attempt to move beyond simple categoriza-

tions, by incorporating more focused measures of racial, ethnic, and cultural

identity.

Limitations aside, results of this project provide fairly convincing evidence

that the Intolerance of Uncertainty Scale behaves similarly across students of four

different racial groups. In addition, these data may suggest that intolerance of

uncertainty could be a fairly universal construct that is associated with

generalized anxiety and worry. Whether this might indicate that treatment

approaches targeting intolerance of uncertainty (e.g., Dugas et al., 2003;

Ladouceur et al., 2000a,b) will be similarly efficacious with various racial and

cultural groups remains an empirical question.

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IUS %26 BDI Description