The Factor Structure of the Eating Disorder Inventory in a

Patient Setting

Carry Welch, BSc., M.A., Ph.D. Anne Hall, M.B., Ch.B.

Claes Norring, M.Sc.

(Accepted 22 November 1988)

The factor structure of a multidimensional, clinically derived measure of the cogni- tive and behavioral characteristics of anorexia nervosa and bulimia, the Eating Dis- order Inventory (EDI), was investigated in a patient setting. The results showed that eight factors corresponding to the eight original subscales of the ED1 were clearly identified in the pattern of factor loadings and that they met conventional standards of internal consistency. The finding of an eight-factor solution using patient re- sponses in this study contrasts with the finding of a clear three-factor solution in an earlier study that employed nonpatient responses. It is suggested that a difference may exist in the meaning of ED1 items to patients and nonpatients. However, it is noted that there is a paucity of information in the eating disorders literature that addresses differences between these groups in their attitudes and beliefs regarding eating, weight, body shape, dieting, and self-esteem. This area is clearly one that warrants closer research attention by those working in the eating disorders.

The Eating Disorder Inventory (EDI; Garner, Olmsted, & Polivy, 1983) is a self- report measure of the cognitive and behavioral characteristics of anorexia ner- vosa and bulimia. The ED1 provides eight subscales, using 64 items, that were derived from clinical and theoretical sources. These subscales are Drive for Thinness, Bulimia, Body Dissatisfaction, Ineffectiveness, Perfectionism, Inter- personal Distrust, Interoceptive Awareness, and Maturity Fears. The ED1 was originally developed for use in a patient setting and in this regard has been used to investigate heterogeneity in anorexia nervosa and bulimia (Mickelide &

Carry Welch, Bk. , MA., Ph.D., is a Research Psychologist at the Department of Psycological Medi- cine, Wellington School of Medicine, Wellington, New Zealand. Anne Hall, M.B., Ch.B., is Associate Professor, Department of Psychological Medicine, Wellington School of Medicine, Wellington, New Zealand. Claes Norring, M.Sc., is a Research Pschologist at the Department of Psychiatry, University Hospital, Uppsala, Sweden. Address reprint requests to Dr. Carry Welch, Department of Psychological Medicine, Wellington School of Medicine, Wellington Hospital, Wellington, New Zealand.

International journal of Eating Disorders, Vol. 9, No. 1, 79-85 (1990) 0 1990 by John Wiley & Sons, Inc. CCC 0276-3478/90/010079-07$04.00

80 Welch, Hall, and Norring

Anderson, 1985; Garner, Garfinkel, & O’Shaughnessy, 1985; Garner, Olmsted, & Garfinkel, 1985; Toner, Garfinkel, & Garner, 1986), to compare parental rela- tionships of women with anorexia nervosa versus bulimia (Humphrey, 1986) and to examine transcultural differences between anorexia nervosa patient groups in Germany and North America (Steinhausen, 1985). In addition, four studies that employed the ED1 were presented at the 1987 International Sym- posium on Eating Disorders in Adolescents and Young Adults, held in Jerusa- lem (Treasure, Holland, Sicotte, & Russell, 1987; Westenhofer, 1987; Neely- Wold, 1987; Isaksson, 1987).

However, the ED1 has also been employed in nonpatient settings. For exam- ple, the ED1 has been used to investigate factors relating to eating psychopa- thology (Eisele, Hertsgaard, & Light, 1986; Lundholm & Littrell, 1986), dimensions of body image disturbance (Grant & Fodor, 1986), heterogeneity in vomiting and nonvomiting university students (Olmsted & Garner, 1986), the prevalence of bulimia in community samples (Hart & Ollendick, 1985; Zucker- man, Colby, Ware, & Lazerson, 1986), and eating attitudes and behaviors in adolescent women (Williams, Schaefer, Shisslak, Gronwaldt, & Comerci, 1986). Furthermore, two nonpatient studies that employed the ED1 were presented at the 1987 International Symposium on Eating Disorders in Adolescents and Young Adults held in Jerusalem (Leon, Perry, & Mangelsdorf, 1987; Colin & Lachter, 1987). An important question exists regarding one of the psychometric properties of the EDI. In particular, the clarity and stability of the ED1 sub- scales in patient settings has not been confirmed by factor analysis. This may be of considerable importance since Welch, Hall, and Walkey (1988) showed that the eight subscales of the ED1 could not be identified among three inde- pendent nonpatient groups, based on an inspection of the pattern of signifi- cant factor loadings for the groups and the results from the comparison of these loadings using the FACTOREP procedure (Walkey & McCormick, 1983). Welch et al. (1988) found that although the Perfectionism subscale was clearly identified in the pattern of factor loadings, the items from the Drive for Thin- ness, Bulimia, and Body Dissatisfaction subscales collapsed together to form a more general subscale that tapped concern with shape, weight, and eating, whereas the Ineffectiveness and Interpersonal Distrust subscales also collapsed together to form a larger subscale that tapped self-esteem. These results under- lined the need for caution among clinicians and researchers in their application of clinical measures of eating disorders to studies of community or nonpatient groups. Also, the results pointed to the need to examine the factor structure of the ED1 using patient responses to determine whether the original eight clini- cally derived factors could be identified in this setting.

METHOD

Patients

The sample comprised 271 eating disorder patients. These included 113 fe- males who met DSM-I11 (American Psychiatric Association, 1980) criteria for anorexia nervosa, bulimia, or eating disorder not elsewhere classified. These women had a mean age of 23.9 years, a mean Quetelet index (a measure of

Factor Structure of ED1 81

body fatness, measured as [weight (kg)/height (m)]*) of 19.6, and attended the Eating Disorders Clinic, Wellington Hospital, Wellington, New Zealand. A sec- ond group included 158 female eating disorder patients who also met DSM-I11 criteria for anorexia nervosa and bulimia and who attended the Outpatient Clinic of the Department of Psychiatry, Uppsala Hospital, Uppsala, Sweden. These women had a mean age of 26.0 years and a mean Quetelet index of 18.8. ED1 data from the New Zealand and Swedish patient groups was combined to provide sufficient patient numbers to meet the minimum subject-to-item ratio for a factor analysis suggested by Nunnally and Wilson (1975).

Procedure and Analysis

The following analyses were carried out:

1. Factor analyses These proceeded along the lines suggested by Walkey (1983), whereby

the initial investigation established whether or not the eight theoretically expected factors could be clearly found and replicated across independent groups. If the eight designated subscales of the ED1 could not be identi- fied from the pattern of significant (i.e., of -40 or above) loadings, then further analyses would be carried out to establish 7,6,5,4,3, and 2 factor solutions.

It is traditional for orthogonal rotation to be used to achieve simple so- lution, since it theoretically identifies the independent factors present among a given interitem correlation matrix. However, some authors sug- gest that oblique rotation is preferable if the factors are highly correlated (e.g., Boyle, 1985), since it will allow the maximum approximation to sim- ple structure to emerge. For this reason, oblique as well as orthogonal ro- tation was explored in the analyses.

2. Coefficients of internal consistency for each subscale Coefficient alphas that approached or equalled .80 would be considered

a minimum requirement in basic research for a test to have acceptable in- ternal consistency (NunnalIy & Durham, 1975).

RESULTS

Table 1 shows the results of the eight-factor analysis of the ED1 using orthog- onal rotation. An inspection of the factor loadings showed that all seven items from the Drive for Thinness subscale loaded significantly (i.e., at .40 or above) on Factor 6, and that two items also loaded significantly on factor 1. For the Ineffectiveness subscale, all 10 items loaded significantly on factor 3, and one item also loaded on factor 8. For the Interoceptive Awareness subscale, all 10 items loaded significantly on factor 2 and one item on factor 5. For the remain- ing subscales, namely Bulimia, Body Dissatisfaction, Perfectionism, Interper- sonal Distrust, and Maurity Fears, the items comprising each loaded significantly and uniquely on one factor only. Specifically, the Bulimia subscale items loaded on factor 5, the Body Dissatisfaction subscale items loaded on fac- tor 1, the Perfectionism subscale items loaded on factor 8, the Interpersonal

82 Welch, Hall, and Norring

Distrust items loaded on factor 7, and the items comprising the Maturity Fears items loaded on factor 4. The results showed therefore, that the eight clinically derived ED1 subscales could be clearly identified in the pattern of factor load- ings obtained from the eight-factor analysis, using the combined New Zealand and Swedish patient sample. The factor analytic results using oblique rotation were the same (in terms of the overall pattern of significant and nonsignificant loadings) as those using orthogonal rotation.

The results of the calculation of the internal consistencies for the eight factors showed that the coefficient alphas obtained for the Interoceptive Awareness,

Table 1. an eight-factor solution of the ED1 using Eating Disorder Patient responses

Factor loadings with orthogonal rotation for

Factors

1 2 3 4 5 6 7 8

ED1 1 10 ED1 7 50 ED111 11 ED116 32 ED125 1 ED132 57 ED149 27 ED1 4 7 ED1 5 16 ED128 1 ED138 25 ED146 13 ED153 26 ED161 11

ED1 2 55 ED1 9 76 ED112 70 ED119 62 ED131 70 ED145 75 ED155 83 ED159 83 ED162 75 ED110 13 ED118 13 ED120 15 ED124 18 ED127 9 ED137 21 ED141 16 ED142 15 ED150 9 ED156 4 ED113 14 ED129 -3 ED136 18 ED143 7

ED163 4 ED152 -4

10 26 0 -2 51 -1 0 18 1 3 29 57 7 12 17 26 -1 20 66 15 5 15 13 3 23 73 13 5 0 14 5 5 53 -18 31 4 5 6 29 49 6 20

21 13 7 19 71 7 10

12 14 -3 64 -1 4 10 6 7 11 82 5 9 2

14 13 -5 67 7 2 0 4 21 1 57 17 -3 3

-2 0 18 77 11 9 6 18 -2 1 48 24 11 8 0 15 5 82 11 11 4 8 13 12 16 32 15 7

15 -7 2 16 16 22 9 8 13 3 13 21 14 6

11 35 0 16 22 -1 3 5 3 6 1 0 1 0 -6

19 8 5 15 12 19 4 1 17 -8 1 -10 11 6

11 1 5 17 12 17 6 13 23 5 5 4 -2 1

15 67 24 9 15 8 13 18 41 3 13 -2 25 39 22 58 2 29 15 21 -2 18 51 15 21 6 10 13 18 64 7 10 25 15 31

15 68 8 2 21 11 17

7 7 4 3 0 8 17 8 24 45 0 23 10 29 28 15 10 7 1 -1 14 68 -9 8 -3 3 4 4 60 22 0 3 -6 21 23 53 -3 5 8 8 -7 -8 66 22 14 -5 7 25 18 55

21 69 0 0 16 18 -4

12 58 13 28 3 5 -1

16 7 10 8 28 0 59

Factor Structure of ED1 83

Table 1. Continued

Factors

1 2 3 4 5 6 7 8 ~

ED115 ED117 ED123 ED130 ED134 ED154 ED157 ED1 8 ED121 ED126 ED133 ED140 ED144 ED147 ED151 ED160 ED164 ED1 3 ED1 6 ED114 ED122 ED135 ED139 ED148 ED158

11 2

20 21 15 0

13 9 5

14 14 11 14 27 9 8 7 2

11 -3 -5

0 2 1 9

-1 10 7 9

25 20 0

73 80 60 61 64 75 52 74 80 55 26 24 5

19 14 15 16 16

4 22 25 30 18 24 5

14 24 33

0 14 23 3

13 25 3 8 7

11 -6 13 8 0 9

16 3 1 2 8 19 9 3 6

9 13 6 12 25 9 12 4 -2 22 3 7 23 3 10 32 8 5 33 14 7 21 21 16 11 5 8 18 1 32 16 0 2 14 9 7 21 39 21 70 5 2 63 5 0 74 0 -4 71 -6 1 60 6 16 68 16 -6 70 -3 11 68 5 3

2 1 -13

71 53 51 54 55 51 68 19 4 3

-4 -1

5 5

19 12 5

13 5 8

16 -5

3 24 0

4 20

- 14 13 21 20 -2

9 2

-4 15

-2 18 2 9 9 8

-1 8 2

-4 19 -3

1 5

Note: Decimal points have been omitted.

Body Dissatisfaction, and Ineffectiveness subscales were above .80, whereas the coefficients for the remaining subscales, ranging from .72 for the Perfec- tionism subscale to .77 for the Drive for Thinness subscale, were marginal but acceptable. Mean ED1 subscale scores (and standard deviations) for the com- bined patient group are as follows: Drive for Thinness 13.1 (6.2j, Bulimia 6.6 (5.6), Body Dissatisfaction 15.6 (8.6), Interoceptive Awareness 12.1 (7.9), Inter- personal Distrust 5.4 (4.4), Interoceptive Awareness 11.1 (7.1), Perfectionism 7.3 (4.5), and Maturity Fears 5.1 (5.0).

D ISCU SSl ON

The evaluation of the reliability and factor structure of the ED1 using patient responses showed that eight factors, that corresponded to the eight clinically derived subscales originally described by Garner et al. (1983), were clearly identified in the pattern of factor loadings, using both orthogonal and oblique rotation to simple solution. These eight factors met conventional standards of internal consistency, although the coefficient alphas were slightly lower than those obtained by Garner et al. (1983), who reported alphas that ranged from .85 for the Drive for Thinness, Interoceptive Awareness, and Interpersonal Dis-

84 Welch, Hall, and Norring

trust subscales to .90 for the Bulimia and Ineffectiveness subscales. An expla- nation of the finding of an eight-factor solution for the ED1 in a patient setting in this study and the finding of a three-factor solution in a nonpatient setting by Welch et al. (1988) may be that a difference exists in the interpretation of the meaning of ED1 items by nonpatients and patients. There is currently a paucity of relevent information in the eating disorders literature that addresses differ- ences between patients and nonpatients in their attitudes and beliefs regarding eating, weight, body shape, dieting, and self-esteem, and future comparative research should focus on these areas. However, the factor analytic findings here provide some evidence of qualitative differences between the groups on these dimensions, although they do not indicate the nature of the differ- ences. Finally, and importantly, the results here showed that the ED1 sub- scales are reliable and psychometrically robust when used in the eating disor- der patient setting and that they will produce interpretable results. Future research into the ED1 should extend the original investigations of Garner et al. (1983) into the discriminant, concurrent, and predictive validity of its sub- scales.

REFERENCES

American Psychiatric Association. (1980). Diagnostic and statistical manual of Mental Disorders (3rd ed.). Washington, D.C.: Author.

Boyle, G. J. (1985). Self-report measures of depression: Some psychometric considerations. British Journal of Clinical Psychology, 24, 45-59.

Colin, V., & Lachter, J. (1987). ED1 and EAT screening for eating disordes among nursing students in Israel: Preliminary data. In Znternational symposium on eating disorders in adolescents and young adults, Jerusalem, May 24-28.

Eisele, J. M., Hertsgaard, D., & Light, H. K. (1986). Factors related to eating disorders in young adolescent girls. Adolescence, 21, 284-290.

Garner, D. M., Garfinkel, P. E., & OShaughnessy, M. (1985). The validity of the distinction be- tween bulimia with and without anorexia nervosa. American Journal of Psychiatry, 142, 581-587.

Garner, D. M., Olmsted, M. P., & Garfinkel, P. E. (1985). Similarities among bulimic groups se- lected by different weights and weight histories. journal of Psychiatric Research, 19, 129-134.

Garner, D. M., Olmsted, M. P., & Polivy, J. (1983). Development and validation of a multidimen- sional eating disorder inventory for anorexia nervosa and bulimia. International Journal of Eating Disorders, 2, 15-34.

Grant, C. L., & Fodor, I. G. (1986). Adolescent attitudes toward body image and anorexic behav- iour. Adolescence, 11, 269-281.

Hart, J. K., & Ollendick, T. H. (1985). Prevalence of bulimia in working and university women. American journal of Psychiatry, 142, 851-854.

Humphrey, L. L. (1986). Structural analysis of parent-child relationship in eating disorders. Journal of Abnormal Psychology, 95, 395-402.

Isaksson, M. (1987). A follow-up study of 222 anorexia nervosa and bulimia patients treated be- tween 1960-1983 from child and youth and adult psychiatric clinics. In International symposium on eating disorders in adolescents and young adults, Jerusalem, May 24-28.

Leon, G. R., Perry, C., & Mangelsdorf, C. (1987). Normative nutritional and psychological devel- opment and the identification of risk factors for the development of an eating disorder. In Znter- national symposium on eating disorders in adolescents and young adults, Jerusalem, May 24-28.

Lundholm, I . K., & Littrell, J. M. (1986). Desire for thinness among high school cheerleaders: Re- lationship to disordered eating and weight control behaviours. Adolescence, 22, 573-579.

Mickelide, A. D., & Andersen, A. E. (1985). Subgroups of anorexia nervosa and bulimia. Validity and utility. Journal of Psychiatric Research, 19, 121 - 128.

Neely-Wold, P. (1987). The affective diathesis as it relates to bulimia. In International symposium on eating disorders in adolescents and young adults, Jerusalem, May 24-28.

Nunnally, J. C., & Durham, R. L. (1975). Validity, reliability, and special problems of measurement in evaluation research. In E. L. Struening and M. Guttentag (Eds.), Handbook of evaluation re- search (Vol. 1). London: Sage Publications.

Factor Structure of ED1 85

Nunnally, J. C., & Wilson, W. H. (1975). Method and theory for developing measures in evalua- tion research. In E. L. Struening and M. Guttentag (Eds.). Handbook of eualuation research (Vol. 1). London: Sage Publications.

Olmsted, M. P., & Garner, D. M. (1986). The significance of self-induced vomiting as a weight- control method among nonclinical samples. International Journal of Eating Disorders, 5 , 683- 700.

Steinhausen, H. C. (1985). Anorexia nervosa. Transcultural comparisons. Pediatrician, 12, 157-163. Toner, B. B., Garfinkel, P. E., & Garner, D. M. (1986). Long term follow-up of anorexia nervosa.

Psychosomatic Medicine, 48, 520-529. Treasure, J., Holland, A,, Sicotte, N., & Russell, G. F. M. (1987). Twins with eating disorders. In

International symposium on eating disorders in adolescents and young adults, Jerusalem, May 24-28. Walkey, F. H. (1983). Simple versus complex factor analysis of responses to multiple scale ques-

tionnaires. Multivariate Behuvioural Research, 18, 401-421. Walkey F. H., & McCormick, I. A. (1983). FACTOREP: A pascal programme to examine factor replica-

tion (Victoria University of Wellington Publications in Psychology, No. 29). Wellington, New Zealand: Victoria University of Wellington.

Welch, G. W., Hall, A., & Walkey, F. H. (1988). The factor structure of the Eating Disorder Inven- tory. Journal of Clinical Psychology, 44, 51-56.

Westenhofer, J. (1987). Self-control in bulimia nervosa. In International symposium on eating disorders in adolescents and young adults, Jerusalem, May 24-28.

Williams, R. L., Schaefer, C. A,, Shisslak, C. M., Gronwaldt, V. H., & Comerci, G. D. (1986). Eat- ing attitudes and behaviors in adolescent women: Discrimination of normals, dieters, and sus- pected bulimics using the Eating Attitudes Test and the Eating Disorder Inventory. International Journal of Eating Disorders, 5, 879-894.

Zuckerman, D. M., Colby, A., Ware, N. C., & Lazerson, J. S. (1986). The prevalence of bulimia among college students. American Journal of Public Health, 76, 1135- 1137.