Psychometric validation of the tridimensional personality questionnaire: Application to subgroups of eating disorders

Psychometric Questionnaire:

Validation of the Tridimensional Personality Application to Subgroups of Eating Disorders

Erin I. Kleifield, Suzanne Sunday, Stephen Hurt, and Katherine A. Halmi Eating disorder patients show extremes of the personality characteristics measured by the Tridimensional Personality Questionnaire (TPQ). For this reason, the TPQ was tested in four subgroups of eating disorder patients. Patients completed the TPQ and their

sponses were compared with a normative sample of women. Results indicated that the TPQ is an internally consistent and valid instrument to use with eating disorder patients. Copyright Q 1993 by W.B. Saunders Company

HARACTER STRUCTURE and personality features of anorectic and bulimic patients have been broadly outlined within multidimensional models of eating disorders.’ While eating disorder patients share many personality attributes (e.g., high levels of depression and anxiety, impaired socialization, low self-esteem), there are also personality characteristics that may differentiate eating disorder subtypes. Bulimic patients have shown a tendency to engage in impulsive and antisocial behaviors (e.g., lying, stealing), to have associated substance abuse problems, to show prominent mood lability and poor self-control, and to have interpersonal difficulties.‘-5 Anorectic patients, on the other hand, have been found to display a temperamental disposition toward behavioral and emotional restraint combined with a strong belief in conventional values.6 Strober’ found that anorectic patients demonstrate an obsessional character structure marked by heightened industriousness and responsibility, highly regimented behavior, and rigid adherence and excessive conformance to rules and standards. He also found that anorectics are interpersonally insecure and show minimal effect. Despite these generalizations in personality descriptions, attempts to find consistencies in personality characteristics within eating disorder subgroups have produced mixed results.3~8-10 Classification of eating disorder subtypes is further complicated by the extent to which personality attributes result from ongoing eating disorder symptomatology or reflect stable traits, and the extent to which they reflect the eating disorder diagnosis or more enduring comorbid personality disorders.“x’“,li Attempts to elucidate differences in personality attributes between anorectic patients who restrict and those who binge and purge (either currently or formerly) have also produced mixed results.9~12.13Furthermore, individuals who are

dually diagnosed within the eating disorders raise theoretical and diagnostic questions about how the personality functioning of these patients is similar to or different from that of those who carry a single diagnosis. Several studies demonstrated that impulsive behaviors including stealing, drug abuse, suicide attempts, selfmutilations, and mood lability are more prevalent in anorectic-bulimics compared with anorectic-restrictors.i3 These difficulties of classification and description may be due to the categorical approach (DSM-III-R criteria) of examining personality. The accurate assessment of personality functioning and classification is necessary to advance our theoretical understanding and pragmatic approach to treating these disorders. Assessing dimensions of personality may produce more consistent and clinically relevant results. The Tridimensional Personality Model was recently proposed as a systematic method for dinical description and classification of both normal and abnormal personality variants.r4J5 The Tridimensional Personality Questionnaire (TPQ) was developed to operationalize and measure behaviors associated with the following three dimensions of personality: novelty seeking ([NS] tendency toward intense exhilaration and excitement), harm avoidance ([HA] tendency toward intense avoidance of aversive stimuli), and reward dependence ([RD] tendency toward intense response to rewards, particularly interpersonal rewards). Behaviors associated with these dimensions are reported to be

re-

C

Comprehensive fsych&ry,

Vol.

34, No. 4 (July/August),

1993:

From the Department of Psychiatry, Cornell L’niversil?, Medical College, Westchester Division, Westchester, NY. Address reprint requests to Erin I. Kleifeld. Ph.D., Depatiment of Psychiatry, Cornell University Medical Center, 21 Bloomingdale Rd. White Plains, NYIO605. Copyright 0 1993 by KB. Saunders Company OOIO-440X19313404-0002$03.OOJO

pp 249-253

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KLEIFIELD ET AL

highly routinized and stable within individuals.14J5 Underlying dimensions of the Tridimensional Personality Model and the psychometric properties of the TPQ have received empirical support with normative samples.14J6 In the clinical realm, the TPQ has been investigated with clinical samples of obsessive-compulsive patients” and in a prospective longitudinal investigation predicting early onset alcohol abuse.18 Despite the descriptive accuracy of the TPQ in characterizing personality attributes of eating disorder patients, its potential usefulness as a dimensional assessment technique, and its successful application with other clinical populations, the TPQ has not been used with eating disorder subjects. Furthermore, the validity of this instrument with an eating disorder population has not yet been tested. Therefore, the purpose of this investigation was to test the psychometric properties of the TPQ with eating disorder patients and determine whether it shows the same psychometric structure as that previously demonstrated in normal subjects. METHOD

Subjects Subjects were 81 females hospitalized for an eating disorder on a psychiatric unit. Patients were divided into the following four subgroups based on diagnosis (according to DSM-III-R) and history: anorectic-restrictors ([AN-R] n = 24) anorectic-bulimics ([AN-B] n = 20) normalweight bulimics with no history of anorexia ([BN] n = 22), and normal-weight bulimics with a past history of anorexia ([B-AN] n = 15). Table 1 shows the mean age and weight (i.e., percent of ideal weight at current weight) for each diagnostic group. Subjects were between the ages of 12 and 44, with a mean age of 22; there was no significant difference in age between diagnostic groups. As expected, there was a significant difference in weight between diagnostic groups [F(3,77) = 48.21, P < .OOl], with both AN-R [F(1,77) = 133.86, P < .OOl] and AN-B [F(1,77) = 55.15, P < .OOl] groups being significantly lower in percent of ideal weight than the two normal-weight bulimic groups. AN-R subjects

Table 1. Clinical Characteristics

of the Four Eating Disorder

Subgroups

Mean age

AN-R

AN-B

(n = 24)

(n = 20)

20.7 (1.6) 21.6 (1.0)

The TPQ’ is a loo-item questionnaire comprised of true/false questions designed to assess three dimensions of personality as follows: NS, HA, and RD. TPQ questions were developed to evaluate behavioral variations on HA, NS, and RD scales separately. These higher-order dimensions are comprised of four lower-order subscales. The NS scale is comprised of exploratory excitability (NSl), impulsivity (NS2), extravagance (NS3), and disorderliness (NS4). The four HA subscales are worry/pessimism (HAl), fear of uncertainty (HA2), shyness with strangers (HA3), and fatigabilityiasthenia (HA4). The subscales measuring RD are sentimentality (RDl), persistence (RD2), attachment (RD3), and dependence (RD4). Weights and ages were obtained from inpatient charts from the Eating Disorders unit. Weights reported are those recorded at the time of testing with the TPQ; all subjects completed the TPQ within 2 weeks of hospital admission.

Analyses To investigate whether the relationships of dimensions of the TPQ among eating disorder patients are similar to those of a normative sample of women, the approaches used with these data were those followed by Svrakic et a1.16 The factor structure of the TPQ was analyzed in several ways. First, correlations among scales were analyzed in several ways. First, correlations among scales were analyzed in both the eating disorder and comparison populations. Second, internal consistency of the scales among eating disorder patients was examined by calculating Cronbach’s coefficient (Y for TPQ scales and subscales. Third, to determine the factor structure of the TPQ, a principal component analysis was performed with factors rotated to an orthogonal solution using a varimax criterion and constraining the solution to three factors. The resulting loadings were then compared with those obtained in the normative sample using a rank-order correlation procedure (Spearman).

(n = 22)

23.9 (1.1)

B-AN (n = 15)

22.1 (1.1)

ideal weight at 74.1 (2.7) 86.7 (2.6)

Measures

RESULTS BN

Mean percent of current weight

were also significantly more emaciated than AN-B subjects [F(1,77) = 10.48, P = .002]. To compare eating disorder subgroups with a normal population, 350 women who completed the TPQ as part of a follow-up evaluation of the 1987 General Social Survey (GSS) from which normative values for the TPQ were derived were used. These women were matched for sex and race to the eating disorder patients and were selected from the general sample of 1,019 respondents of the GSS; mean age of the 350 women was 45.5 (SD = 17.8) with a range of 18 to 88. Detailed information on the sampling method and demographic characteristics of GSS respondents can be found in the study by Svrakic et a1.t6

110.3 (2.4) 116.2 (3.9)

As predicted by the theory, correlations among scales were low (Table 2). a-coefficients are presented for eating disorder patients and the female comparison group in Table 3. In general, a-coefficients for eating disorder pa-

251

TPQ IN EATING DISORDER SUBGROUPS

Table 2. Correlations Among TPQ Scales for Eating Disorder

Table 4. Factor Loadings of TPQ Subscales in a B-Factor and

Patients and the Normative Female Sample

4.Factor Solution for Eating Disorder Patients and the

HA

NS

Eating disorder

RD

Normative Female Sample

-

Patients

patients In = 81) Factor 1

NS HA

.ll

RD

.02

Normative

-.13

female sample (n = 350)

NS HA

-.16

RD

.I7

-.I4

tients were higher than those for the comparison group, indicating that the TPQ is internally consistent in the eating disorder population. HA and its subscales had the highest cxvalues, ranging from .68 to .88. Three subscales of NS performed well (NS2, NS3, and NS4); NSl had a relatively lower (Yof .45. RD performed the least well of all the scales. RD4 was the least internally consistent of the subscales for both the eating disorder group (CX= .21) and the comparison group (CY= .38). Whereas RDl was low for the comparison group (a = .39), this CY was considerably higher for the eating disorder group (.78), suggesting that its internal consistency varies between these samples. Standardized factor loadings following rotation are provided for both eating disorder patients and comparison subjects (Table 4). In the 3-factor solution, factor loadings for subscales are consistently high with one exception; RD2 did not load highly on any of the factors. Two Table 3. Cronbach’s 01for TPCI Scales and Subscales in Eating Disorder Patients and the Normative Female Sample Eating Disorder

Normative

Patients

Female Sample

(n = 81)

(n = 350)

NSl

.45

.54

NS2

.67

.55

NS3

.63

.63

NS4

.53

.47

NS

.77

.73

HA1

.76

.65

HA2

.68

.65

HA3

.75

.74

HA4

.82

.74

HA

.88

.85

RDl

.78

.39

RD2

.60

.57

RD3

.79

.64

RD4

.21

.38

RD

.7l

.61

Factor 2

Comparison Factor 3

Factor 1

Group

Factor 2

Factor 3

.I0

.25

-.7l

.07

.21

.57

-.21

- .31

.64

-.22

.67

-.28

NSl

.29

NS2

.77

NS3

.72

-.03

NS4

.82

- .06

HA1

.28

.76

.12

.46

.57

.03

HA2

.03

.75

.37

.I3

.76

.29

HA3

.I2

.66

-.31

.25

.72

HA4

.51

.55

-.I2

.31

.54

.I0

.21

.66

-.16

-.04

-.26

.02

.07

p.16

- .23

.I2

- .33

.63

.33

- .38

.56

-.02

.73

.23

-.02

.74

RDl RD2

.14

RD3 RD4

-.07

-.72 .17

.03 -.12

.09 -.27

.03 -.lO .51

Patients Factor 1

Factor 2

Factor 3

NSl

.28

- .73

.12

NS2

.80

.16

.18

NS3

.67

- .03

.04

NS4

.84

- .08

HA1

.33

.75

Ha2 HA3 HA4

-.oo

.76

-.16 .08 .34

Factor 4 -.Ol

.06 -.32 .04 .I6 .03

.08

.66

-.31

-.25

.50

.54

-.15

-.08

RDl

-.03

RD2

-.lO

.22

.63

.31

-.04

.Ol

.88

RD3

.31

- .31

.64

.05

RD4

.02

-.02

.77

.38

interesting findings were that NSl loaded with a high negative value on the HA factor, and HA4 loaded with a high positive value on both the NS factor and the HA factor. As shown, the same general pattern of results characterized both the eating disorder and normal populations. Results of a Spearman correlation procedure comparing factor loadings in eating disorder and normal populations revealed that the factor structure of the instrument was consistent across populations. Rank-order correlations of the factor loadings of eating disorder patients and normal subjects were as follows: HA factor, r = .95, and P < ,001; NS factor, r = .76 and P < .Ol; RD factor, r = .71 and P < .02. A 4-factor solution was calculated because of the low factor loading of RD2 on any of the first three factors. As anticipated, all subscales showed the same pattern of loadings except RD2, which loaded .89 on factor 4 (Table 4).

252

KLEIFIELD ET AL

DISCUSSION

This study is the first to apply Cloninger’s TPQ to eating disorder subjects. The internal consistency of the TPQ was inspected to determine whether relationships among its dimensions were similar in eating disorder patients and a normative sample. Results of this study indicated that the TPQ is an internally consistent instrument for use with eating disorder patients. In general, a-coefficients for patients were higher than those for the comparison group, and all scales produced respectable a-coefficients. The internal consistency of the HA scale was the highest and was followed by the consistencies of NS and RD, respectively. This same result was obtained in a prior investigation with a normative sample.16 The TPQ performed largely in ways predicted by the theory. Standardized factor loadings following rotation showed that most subscales loaded highly on one of the three factors as predicted by Cloninger. There were three exceptions to his predictions. The first exception was the NSl subscale, which loaded more highly on the HA scale (inversely) than on the NS scale. This finding, i.e., exploratory tendencies are inversely related to HA, is nevertheless consistent with Cloninger’s mode1.14J5 The second exception was that NS4 loaded equally well on NS and HA factors. The third exception to the expected pattern of loadings was the RD2subscale, which did not load highly on any of the factors.

It is noteworthy that results obtained in an eating disorder sample were identical to those obtained in a prior investigation with a normative sample,16 indicating that relationships among dimensions of the TPQ are similar across populations. It also suggests that the TPQ may require some modest restructuring, with the RD2 subscale as a separate factor and the NSl subscale as part of the HA factor. The TPQ factor structure was replicated among eating disorder patients and shows considerable promise as an instrument for characterizing the underlying personality structure of patients with eating disorder pathology. Comparisons of personality style among eating disorder patients and with normal controls, and the ability to assess changes in personality characteristics, require dimensional measurements of underlying personality structure. The TPQ, because of its focus on personality variables relevant for understanding the personality structure of patients with eating disorders, offers promise as a tool for assessing the impact of treatment programs in ameliorating the more extreme expressions of behavior often seen with this population.

ACKNOWLEDGMENT The authors wish to thank Robert C. Cloninger, Dragan M. Svrakic, M.D., and Thomas R. Przybeck, for their assistance in preparation of the manuscript.

M.D., Ph.D.,

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