.~dttic’tivr Buhariors. Vol. Ii. pp. 283-239. Printed in the USA. All rights reserved.
1992
03064603192
CopyrightQ
$5.00
+ .Oil
1992 Pergamon Press Ltd.
VALIDITY OF THE MIZES ANORECTIC COGNITIONS SCALE: A COMPARISON BETWEEN ANORECI’ICS, BULIMICS, AND PSYCHIATRIC CONTROLS J. SCOTT MIZES Case Western Reserve University School of Medicine Abstract - The Mizes Anorectic Cognitions scale (MAC) was developed to assess cognitions relevant to anorexia and bulimia net-vosa. It assesses three areas: rigid weight regulation. weight and approval, and excessive self-control as a component of self-esteem. Previous research has supported the validity and reliability ofthe scale. The purpose ofthe present study was to extend previous work to include anorectic patients, examine the specificity ofthe scale by makingcomparisons to a psychiatric (rather than normal) control group. and secondarily. to conduct a preliminary comparison of bulimics and anorectics. Results showed that for the total MAC score and the subscales, bulimics and anorectics scored higher than psychiatric controls. though they did not differ from each other.
Several authors have emphasized cognitive variables in anorexia and bulimia nervosa (Fairburn, 1985; Garner & Bemis, 1982; Mizes, 1985). These cognitive variables include a variety of attitudes, beliefs, and self-statements regarding food, eating behavior, and body weight. One outgrowth of these theoretical perspectives has been the development of several questionnaires to assess these presumed cognitions. For example, questionnaires that have been developed include the Eating Attitudes Test (Garner & Garfinkel, 1979), the Bulimia Cognitive Distortions Scale (Schulman, Kinder, Powers, Prange, & Gleghorn, 1986), and the Bulimic Thoughts Questionnaire (Phelan, 1987). To date, only the Eating Attitutes Test has had extensive investigation of its reliability and validity. Additionally, none of these scales were designed to specifically assess the three cognitive domains articulated by Gamer and Bemis (1982) that is, rigid weight regulation, weight as the basis of approval, and self-control as a component of self-esteem. In contrast, the Mizes Anorectic Cot&ions questionnaire (MAC, Mizes & Klesges, 1989) was developed based on the tripartite cognitive model described by Garner and Bemis (1982). The MAC is a 33-item, Likert format questionnaire which has Rigid Weight Regulation, Approval and Weight, and Self-Control and Self-Esteem subscales. Initial research on the validity and reliability of the MAC has been encouraging. In a nonclinical sample, Mizes and Klesges (1989) found that the MAC was correlated with measures of eating pathology, and it showed expected weight and sex differences. Additionally, the subscales were empirically verified via factor analysis, and high internal consistency was found (coefficient alphas .75-.91). Mizes (1988) found that the MAC discriminated bulimics from controls, accounting for 60% of the between groups variance. Mizes ( 1990) found that high MAC scorers had a greater general emphasis on weight regulation, rated higher various benefits of losing or maintaining weight, used Portions of this paper were presented at the Association for the Advancement of Behavior Therapy. Washington. DC, November, 1989. This research was supported in part by a grant from the Geisinger Research Foundation. Thanks to Anne Farrell and Michelle Arbitell for their assistance in data collection and analysis. Requests for reprints should be sent to J. Scott Mizes, Ph.D., ABPP, Department of Psychiatry, MetroHealth Medical Center, Case Western Reserve University School of Medicine, 2500 Metro Health Dr., Cleveland, OH 44 109. 283
78-l
1. SCOTT hIli!ES
more calorie restriction strategies. and to a lesser extent, used more strategies to increase real or presumed calorie expenditure. Mizes (199 1) supported the construct validity of the MAC in a nonclinical sample, replicated the component structure via factor analysis, replicated high internal consistency (coefficient alphas .76-.93), and demonstrated good temporal reliability (test-retest correlation .78). To date, research on the MAC has focused on bulimics and general population samples. No study has yet assessed the MAC in anorectic patients. Also. previous research on discriminant validity has used clinically asymptomatic persons as controls, No study has assessed the MAC in eating disorder patients and compared them to psychiatric controls. This is necessary in order to show that the cognitions assessed by the MAC are specific to eating disorders and not representative ofgeneral psy-chopathology. Thus far, no study has compared the responses of bulimics and anorectics on the MAC. W’hile the primary purpose of the study was to assess the M.4C’s validity in anorectics. a secondary aim was to conduct a preliminary comparison of bulimics’ and anorectics’ scores on the MAC. In order to address these issues, the current study compared M.4C scores in bulimics. anorectics, and psychiatric controls.
bl E T H 0 D
Subjects
Participants were 15 bulimics, 8 anorectics, and 11 psychiatric controls, all of whom had presented for treatment at the psychiatry department of a general medical surgical hospital. With the exception of one male each in the anorectic and control group. and two males in the bulimia group, all the other participants were females.’ All the subjects were Caucasian and largely from middle-class and above households. All patients participated in the early phase oftheir treatment and the sample included both outpatients and inpatients in all three groups. All patients were given a structured interview by a trained research assistant to assess the presence ofanorexia and bulimia nervosa according to DSM-III-R criteria (American Psychiatric Association. 1987). Although the interviewers were blind as to the patients’ specific eating disorder diagnosis, they were not blind as to the hypotheses being investigated. The structured interview consisted of a rating of the presence or absence of each of the DSM-III-R criteria for bulimia and anorexia nervosa. The interview was used to verify the diagnosis given each patient by their treating clinician, and the interview was always conducted by a research assistant who was not the treating clinician. For the eating disorder groups, the clinician’s diagnosis was confirmed by the interview in all instances. For the psychiatric comparison group, the interview did not identify any cases of an eating disorder which had not been diagnosed by the treating clinician. The psychiatric control group was selected by an initial screening of the charts of patients actively being seen in clinic or in the hospital to determine that they met basic inclusion criteria regarding diagnosis and weight. Patients were excluded if they had a history of an eating disorder, or if their current diagnosis was mental deficiency, organic mental disorder, schizophrenia, psychosis, paranoid disorder, or dissociative disorder. Futhermore, they were excluded if the structured interview revealed a current eating disorder. They also had to score at or between the 25th and 75th percentile of age, sex, ‘Due to the unexpected recruitment of males in the eating disorder groups. recruitment ofthe control group was altered to seek out one male. As best as possible, this helped equate the percentage of males in each group.
Validity
of the MAC
285
and height-adjusted weight norms (Department of Health, Education, and Welfare, 1979). Finally, patients had to score below one standard deviation under the mean on the Gormally Binge Scale (BS, see Measures) to help exclude even subclinical eating pathology. Of the patients invited to participate in the study after the initial chart review, four were excluded because oftheir BS scores and/or failure to meet the weight criteria upon actual weighing. Diagnoses for the psychiatric control group were taken from the initial evaluation in the patient’s chart. The final group had the following diagnoses: major depression (3); simple phobia (1); marital discord ( 1); manic depression ( 1): obsessive compulsive disorder (1); dysthymia (2); migraines (1); and conduct disorder (1). Thus, 55% of of the psychiatric comparison group had an affective disorder. To be in the bulimia or anorexia groups, participants had to fulfill the respective DSM-III-R diagnostic criteria, based on the structured interview. There were no potential eating disorder participants excluded for failing to meet DSM-III-R criteria. To be in the bulimia group, in addition to meeting DSM-III-R criteria, participants also had to weigh less than or equal to the DHEW 75th percentile. This was done to eliminate any confounding effects of being bulimic and obese. Measwes As described above, to assist in subject selection, and also as a check on group assignment, all participants were administered the Gormally Binge Scale (Gormally, Black, Daston. & Rardin, 1982), which is a frequently used pencil-paper measure of binge eating tendencies. Scores on the BS range from 16-62. It was hypothesized that the group assignment would be supported if bulimics scored higher on the BS than anorectics, and if both scored higher than the psychiatric controls. As a further check on group assignment, they were also given the Eating Disorders Inventory (EDI, Garner & Olmsted, 1984). The ED1 is a frequently used pencil-paper measure of primary and secondary symptoms of bulimia and anorexia nervosa. It was hypothesized that the group assignment would be further supported if both eating disorder groups scored higher on the ED1 total score than did the psychiatric controls.’ All patients were given the MAC. The MXC has been extensively described elsewhere (Mizes & Klesges, 1989).’ Scores range from 33-165. A normative ideal weight for each participant was determined using the 50th percentile of the age, sex, and height adjusted DHEW (1979) norms. Finally, the subjects were classified as either under- or nomal weight using the 25th percentile of the DHEW norms as the cutoff point. Procedure Psychiatric patients meeting the chart review inclusion criteria were given the BS, weighed, and had their height measured. Beyond this point, all groups proceeded similarly. After administering the structured interview, subjects completed the EDI, MAC, and BS (if not already completed). The questionnaires were administered in random order. All subjects were paid $10 for their participation. 2Scoring the ED1 results in several subscale scores, and a total score per se is not generated. However. for brevity. the subscale scores were added to form a total score. Because the purpose was to use the ED1 to confirm the clinical diagnosis of an eating disorder, and not to examine subscale differences on the EDI. this seemed appropriate. Readers interested in results for the individual ED1 subscales are invited to write the author. 3Copies of the ?vl.AC, scoring criteria, and an IBM scoring program are available by writing the author.
286
J. SCOTT
MIZES
Table I, Means and standard deviations for eating disorder and selection variables for bulimcs, anorectics. and psychiatric controls Variable Binges/uk’ Vomiting/wk Weight (Ibs) EDI (total) Binge scale
Bulimics 9.5 8.8 128.2 97.7 34.4
(8.0) (9.2) ( 18.0)“b (37.3)” (8.7)
Anorectics 3.5 6.6 107.6 69.5 23.6
(6.9) ( I I .9)‘b (23.9)b (31.7) (7.8)
Controls 0 (0)” 0 (OP 13’.7(21.5) 19.1 (I 1.9) 3.7 (2.7)
~Vorc. hleans in rows vvith like superscripts are not significantly different. ‘Numbers in parentheses are standard deviations.
RESULTS
Several variables were examined via one-way ANOVAs to confirm group assignment, as well as to confirm equivalence on other relevant variables. Means, standard deviations, and planned pairwise comparisons @ I .05) are presented in Table 1. The groups differed significantly on self-reported binges per week, F(2,3 1) = 7.6, p = .002. Bulimics had significantly more binges than either anorectics or controls, both who did not differ from each other. The groups differed significantly on self-reported vomiting episodes per week, F(2, 31) = 3.6, p = .04. Though bulimics and anorectics did not differ from each other, only bulimics vomited more than controls. Weight was significantly different, F(2,3 1) = 3.8, p = .03. Anorectics weighed significantly less than controls, although the anorectics showed a trend (p = .07) toward weighing less than the bulimics. Regarding relative weight classification, all of the anorectics were underweight, all of the psychiatric controls were normal weight, and all but one of the bulimics were normal weight. The overall difference was significant, F(2, 31) = 94.4, p < .OOl. Both bulimics and controls had a significantly higher relative weight classification than anorectics, though they did not differ from each other. EDI total scores were significantly different, F(2, 3 1) = 2 1.9, p < .OOl. Both anorectics and bulimics scored higher than controls. Finally, the groups differed significantly on the BS, F(2.3 1) = 59.8, p < .OO1. Bulimics scored higher than anorectics, both of which scored higher than controls. The groups did not differ on age, M = 22.4, SD = 6.9, F(2, 31) = 1.3,~ = .28; normative ideal weight, A4 = 136.2 lbs, SD = 20.5, F(2, 31) = .36, p = .70: or height, M = 64.9 inches, SD = 4.1, F(2, 31) = .26, p = .77. MAC means and standard deviations for the three study groups are presented in Table 2. For the total score, the one way analysis of variance was significant, F(2, 3 1) = 36.8, p < .OO1, multiple R' = .70. The groups were significanly different on the Rigid Weight Regulation subscale, F(2,3 1) = 38.6, a < .OOI, multiple R* = .7 1. For the SelfControl scale, the effect was also significnat, F(2, 3 1) = 38.3, p < .OOl, multiple RZ = .7 I. Finally, for the Approval subscale, a significant effect was found, F(2, 3 1) = 5.4, P = .009, multiple R' = .26. Planned comparisons for all four scores revealed that both bulimics and anorectics scored significantly higher than controls, though they did not differ from each other. The MAC total scores and subscales were correlated with the EDI total score and subscales for the total sample.4 For the MAC total score, the correlation with the ED1 4Readers author.
interested
in the correlation
matrix
for the individual
MAC
and ED1 subscales may write the
287
Validity of the MAC
Table 2. Total MAC and subscale means and standard deviations for bulimics. anorectics, and psychiatric controls Bulimics Total’ U’gt. Reduction Self-Control Wgt. & Approval
119.5 (20.5) 73.0 (14.1) 26. I (2.7) 20.4 (5.8)
Anorectics 115.6 (14.7) 71.3 (9.7) 25.8 (2.7) 18.6 (5.3)
Controls 65.1 (12.3) 35.0 (8.7) 16.4 (3.5) 13.7 (3.9)
.Vote. For all comparisons. bulimicsdid not differ from anorectics. though both differed from controls. ‘Numbers in parentheses are standard deviations.
total score was .80, p < .OO1. Correlations with the subscales ranged from .42-.84, and all were significant. The Self-Control subscale correlated significantly with the total EDI, r = .78, p < .OOl. Correlations with ED1 subscales ranged from .38-.80, and all were significant. Rigid Weight Regulation correlated significantly with the Total EDI, r = .79, p < .OOl, and subscale correlations ranged from .41-.86 (all significant). Finally, the Approval subscale correlated with the total EDI, r = .56, p = .OOl. Correlations with ED1 subscales ranged from .28-.60, and all but two were significant. The two non-significant correlations were for the ED1 Perfectionism and Interpersonal Distrust subscales. DISCUSSION
Results ofthe present study further support the criterion-related validity ofthe MAC. Despite the small sample size necessitated by the difficulties of recruiting clinical samples according to strict criteria, large differences were found between the eating disorder groups and a psychiatric comparison group. These results replicate previous findings with bulimic patients, and extend the demonstration of criterion-related validity to anorectics. While the cognitive distortions hypothesized to be relevant to bulimia and anorexia are very similar, it is nonetheless important to demonstrate the MAC’s validity in both populations. Additionally, this is the first time the criterion-related validity of the MAC’s subscales had been assessed in a clinical population. As in previous research, the MAC showed good concurrent validity, this time with reference to the EDI. However, the Weight and Approval subscale appeared to be less strongly associated with the ED1 than were the other two subscales. As in previous research, the MAC accounted for a substantial portion of the between groups variance. In this study, the MAC accounted for 70% of the variance, in Mizes ( 1988) 60%. Thus, the cognitions assessed by the MAC appear to be a prominent feature of anorexia and bulimia. Also, by using a psychiatric control group, this study suggests that the cognitions assessed by the MAC do not appear to be merely reflective of general psychopathology. Rather, they reflect the specific psychopathology of bulimia and anorexia. Although other clinical or nonclinical groups (such as the obese) who have weight-related concerns may endorse these congitions to some extent (see Mizes & Klesges, 1989), it is suggested that the most extreme endorsement of these cognitions is associated with clinical bulimia and anorexia nervosa. Of course, this requires direct empirical investigation.
288
J. SCOTT
MIZES
A secondary purpose of the study was to conduct a preliminary assessment of potential differences between anorectics and bulimics on the MAC. Though no specific prediction was made. it is interesting that bulimics and anorectics did not dilfer on MAC scores. Thus, the current findings do not shed any light on differences between anorexia and bulimia nervosa. Perhaps this is inherently a difficult discrimination because a substantial portion of patients shift back and forth between the two diagnostic entities. and because of inadequacies in the diagnostic criteria (Mizes, in press). Indeed, various theorists have articulated essentially similar cognitive distortions for the two disorders (i.e.. Fairburn & Garner, 1986). Alternatively, it is also possible that the MAC does not assess psychological constructs which discriminate anorexia and bulimia. Also, it must be acknowledged that the small sample size may have made it difficult to detect small. though real, differences due to low statistical povver. Hovvever. inspection of bulimics’ and anorectics’ MAC means does not even suggest a trend toward a statistically significant difference. The group differences were not even one-fourth ofthe sample standard deviations in most cases. To put this into perspective, a power analysis reveals that 140- 180 bulimics. and an equal number of anorectics would be needed to detect a significant difference for an effect this small, with power set at a conventional .80 (Cohen, 1977). The practical difficulties of recruiting that many eating disorder patients is obvious. Also, the clinical meaningfulness of a difference that small can be questioned. Though the body of research supporting the validity and reliability of the IMAC is growing, further research is clearly warranted. Research on large samples of bulimic and anorectic patients to further examine component structure and reliability would be useful. It is also important to compare bulimics and anorectics to others with eating-related concerns, such as the obese, restrained eaters, and subclinical bingers. In addition to helping establish the discriminant validity with subclinical or alternate forms of eating pathology, this may highlight differences in the psychopathology of the various eating pathology groups. Finally, it will be important to assess the MAC’s validity using in vivo assessment of cognitions as the criterion. REFERENCES American Psychiatric Association. (1987). Diagnosfic und sroris~ical rnanwl ql’~rrwra/ drsorders (3rd ed.). Washington. DC: Author. Cohen 1. ( 1977). Power ana/j,sisfor rhc behavioralsciences (revised cdirionj. Nem j’ork: Academic Press. Department of Health. Education. and Welfare. (1979). W’eighr by hc>ighr and agejitr adrrlrs 18-74 j‘ears LT..% 197/-19i4 (DHEW Publication No. 79-1656, Series I I. No. 280). Bethesda, MD: Author. Fairburn, C. G. (1985). A cognitive behavioral treatment ofbulimia. In D. M. Garner& P. E. Gartinkel (Eds.). Handbook c!Tps?rltoiherup?.for anore.uia nervosa and bulimia (pp. I63- 197). Sew York: Guilford. Fairburn. C. G., 6r Garner, D. M. ( 1986). The diagnosis of bulimia nen’osa. It~tc~rtfariotzalJoltrnal cft5zritz.q Disorders,
5.403-4
19.
Garner,
D. M.. 8: Bemis K. M. (1982). A cognitive behavioral approach to anorexia nervosa. Cogniiiw Therapj, and Research. 6, I23- 150. Garner, D. M.. 8: Gariinkel, P. E. (1979). The Eating Attitudes Test: An index ofthe symptoms ofanorexia nervosa. Psj,chologicalMedicine. 9, 273-279. Garner. D. M.. & Olmstead. M. P. (I 981). Earing Disorder Inventor! ttmt~uul. Odessa, FL: Psychological Assessment Resources, Inc. Cormally. 1.. Black, S.. Daston, S.. & Rardin. D. (1982). The assessment ofbinge eating severity among obese persons. Addicliw Behaviors, 7,47-55. Mizes, J. S. (1985). Bulimia: A review of its symptomatology and treatment. .-ld\wtws in Behuvirv Resenrch and Therapy.
7,9
I-
142.
Mizes, J. S. (1988). Personality characteristics nitive behavioral perspective. Inrernational
of bulimic Journal
and non-eating oj‘Enring
disordered
Dtsorders.
female controls:
7, 54 I-550.
a cog-
Validity
of the MAC
289
Mizes. J. S. (1990).Criterion-related validity of the Anorectic Cognitions questionnaire. Addicrivr Behaviors. 15, 153-163. Mizes. J. S. (I 99 I). Construct validity and factor stability of the Anorectic Cognitions questionnaire. ._(&icrirt> Behariors. II. 589-594. Mizes. J. S. (in press). Bulimia nervosa. In A. S. Bellack & M. Hersen (Eds.), Handhook o/hluxior rhcrclpl in rite ps~chiurric scffing New York: Plenum. Mizes. J. S.. & Klesges. R. C. (1989). Validity. reliability. and factor structrue of the Anorectic Cognitions questionnaire. .-ldd;cfi~eBr,/zaviors. 14, 589-594. Phelan. P. W. (1987). Cognitive correlates of bulimia: The Bulimic Thoughts Questionnaire. Inirrnarional Journal yfflnliny Disorders. 6. 593-607. Schulman. R. G.. Kinder. B. N.. Powers. P. S.. Prange. M.. & Gleghorn, A. (1986). The development of a scale to measure cognitive distortions in bulimia. Jorrma/ o~Pt~rsonalit~ Assesanenf. 50,630-639.
1992
03064603192
CopyrightQ
$5.00
+ .Oil
1992 Pergamon Press Ltd.
VALIDITY OF THE MIZES ANORECTIC COGNITIONS SCALE: A COMPARISON BETWEEN ANORECI’ICS, BULIMICS, AND PSYCHIATRIC CONTROLS J. SCOTT MIZES Case Western Reserve University School of Medicine Abstract - The Mizes Anorectic Cognitions scale (MAC) was developed to assess cognitions relevant to anorexia and bulimia net-vosa. It assesses three areas: rigid weight regulation. weight and approval, and excessive self-control as a component of self-esteem. Previous research has supported the validity and reliability ofthe scale. The purpose ofthe present study was to extend previous work to include anorectic patients, examine the specificity ofthe scale by makingcomparisons to a psychiatric (rather than normal) control group. and secondarily. to conduct a preliminary comparison of bulimics and anorectics. Results showed that for the total MAC score and the subscales, bulimics and anorectics scored higher than psychiatric controls. though they did not differ from each other.
Several authors have emphasized cognitive variables in anorexia and bulimia nervosa (Fairburn, 1985; Garner & Bemis, 1982; Mizes, 1985). These cognitive variables include a variety of attitudes, beliefs, and self-statements regarding food, eating behavior, and body weight. One outgrowth of these theoretical perspectives has been the development of several questionnaires to assess these presumed cognitions. For example, questionnaires that have been developed include the Eating Attitudes Test (Garner & Garfinkel, 1979), the Bulimia Cognitive Distortions Scale (Schulman, Kinder, Powers, Prange, & Gleghorn, 1986), and the Bulimic Thoughts Questionnaire (Phelan, 1987). To date, only the Eating Attitutes Test has had extensive investigation of its reliability and validity. Additionally, none of these scales were designed to specifically assess the three cognitive domains articulated by Gamer and Bemis (1982) that is, rigid weight regulation, weight as the basis of approval, and self-control as a component of self-esteem. In contrast, the Mizes Anorectic Cot&ions questionnaire (MAC, Mizes & Klesges, 1989) was developed based on the tripartite cognitive model described by Garner and Bemis (1982). The MAC is a 33-item, Likert format questionnaire which has Rigid Weight Regulation, Approval and Weight, and Self-Control and Self-Esteem subscales. Initial research on the validity and reliability of the MAC has been encouraging. In a nonclinical sample, Mizes and Klesges (1989) found that the MAC was correlated with measures of eating pathology, and it showed expected weight and sex differences. Additionally, the subscales were empirically verified via factor analysis, and high internal consistency was found (coefficient alphas .75-.91). Mizes (1988) found that the MAC discriminated bulimics from controls, accounting for 60% of the between groups variance. Mizes ( 1990) found that high MAC scorers had a greater general emphasis on weight regulation, rated higher various benefits of losing or maintaining weight, used Portions of this paper were presented at the Association for the Advancement of Behavior Therapy. Washington. DC, November, 1989. This research was supported in part by a grant from the Geisinger Research Foundation. Thanks to Anne Farrell and Michelle Arbitell for their assistance in data collection and analysis. Requests for reprints should be sent to J. Scott Mizes, Ph.D., ABPP, Department of Psychiatry, MetroHealth Medical Center, Case Western Reserve University School of Medicine, 2500 Metro Health Dr., Cleveland, OH 44 109. 283
78-l
1. SCOTT hIli!ES
more calorie restriction strategies. and to a lesser extent, used more strategies to increase real or presumed calorie expenditure. Mizes (199 1) supported the construct validity of the MAC in a nonclinical sample, replicated the component structure via factor analysis, replicated high internal consistency (coefficient alphas .76-.93), and demonstrated good temporal reliability (test-retest correlation .78). To date, research on the MAC has focused on bulimics and general population samples. No study has yet assessed the MAC in anorectic patients. Also. previous research on discriminant validity has used clinically asymptomatic persons as controls, No study has assessed the MAC in eating disorder patients and compared them to psychiatric controls. This is necessary in order to show that the cognitions assessed by the MAC are specific to eating disorders and not representative ofgeneral psy-chopathology. Thus far, no study has compared the responses of bulimics and anorectics on the MAC. W’hile the primary purpose of the study was to assess the M.4C’s validity in anorectics. a secondary aim was to conduct a preliminary comparison of bulimics’ and anorectics’ scores on the MAC. In order to address these issues, the current study compared M.4C scores in bulimics. anorectics, and psychiatric controls.
bl E T H 0 D
Subjects
Participants were 15 bulimics, 8 anorectics, and 11 psychiatric controls, all of whom had presented for treatment at the psychiatry department of a general medical surgical hospital. With the exception of one male each in the anorectic and control group. and two males in the bulimia group, all the other participants were females.’ All the subjects were Caucasian and largely from middle-class and above households. All patients participated in the early phase oftheir treatment and the sample included both outpatients and inpatients in all three groups. All patients were given a structured interview by a trained research assistant to assess the presence ofanorexia and bulimia nervosa according to DSM-III-R criteria (American Psychiatric Association. 1987). Although the interviewers were blind as to the patients’ specific eating disorder diagnosis, they were not blind as to the hypotheses being investigated. The structured interview consisted of a rating of the presence or absence of each of the DSM-III-R criteria for bulimia and anorexia nervosa. The interview was used to verify the diagnosis given each patient by their treating clinician, and the interview was always conducted by a research assistant who was not the treating clinician. For the eating disorder groups, the clinician’s diagnosis was confirmed by the interview in all instances. For the psychiatric comparison group, the interview did not identify any cases of an eating disorder which had not been diagnosed by the treating clinician. The psychiatric control group was selected by an initial screening of the charts of patients actively being seen in clinic or in the hospital to determine that they met basic inclusion criteria regarding diagnosis and weight. Patients were excluded if they had a history of an eating disorder, or if their current diagnosis was mental deficiency, organic mental disorder, schizophrenia, psychosis, paranoid disorder, or dissociative disorder. Futhermore, they were excluded if the structured interview revealed a current eating disorder. They also had to score at or between the 25th and 75th percentile of age, sex, ‘Due to the unexpected recruitment of males in the eating disorder groups. recruitment ofthe control group was altered to seek out one male. As best as possible, this helped equate the percentage of males in each group.
Validity
of the MAC
285
and height-adjusted weight norms (Department of Health, Education, and Welfare, 1979). Finally, patients had to score below one standard deviation under the mean on the Gormally Binge Scale (BS, see Measures) to help exclude even subclinical eating pathology. Of the patients invited to participate in the study after the initial chart review, four were excluded because oftheir BS scores and/or failure to meet the weight criteria upon actual weighing. Diagnoses for the psychiatric control group were taken from the initial evaluation in the patient’s chart. The final group had the following diagnoses: major depression (3); simple phobia (1); marital discord ( 1); manic depression ( 1): obsessive compulsive disorder (1); dysthymia (2); migraines (1); and conduct disorder (1). Thus, 55% of of the psychiatric comparison group had an affective disorder. To be in the bulimia or anorexia groups, participants had to fulfill the respective DSM-III-R diagnostic criteria, based on the structured interview. There were no potential eating disorder participants excluded for failing to meet DSM-III-R criteria. To be in the bulimia group, in addition to meeting DSM-III-R criteria, participants also had to weigh less than or equal to the DHEW 75th percentile. This was done to eliminate any confounding effects of being bulimic and obese. Measwes As described above, to assist in subject selection, and also as a check on group assignment, all participants were administered the Gormally Binge Scale (Gormally, Black, Daston. & Rardin, 1982), which is a frequently used pencil-paper measure of binge eating tendencies. Scores on the BS range from 16-62. It was hypothesized that the group assignment would be supported if bulimics scored higher on the BS than anorectics, and if both scored higher than the psychiatric controls. As a further check on group assignment, they were also given the Eating Disorders Inventory (EDI, Garner & Olmsted, 1984). The ED1 is a frequently used pencil-paper measure of primary and secondary symptoms of bulimia and anorexia nervosa. It was hypothesized that the group assignment would be further supported if both eating disorder groups scored higher on the ED1 total score than did the psychiatric controls.’ All patients were given the MAC. The MXC has been extensively described elsewhere (Mizes & Klesges, 1989).’ Scores range from 33-165. A normative ideal weight for each participant was determined using the 50th percentile of the age, sex, and height adjusted DHEW (1979) norms. Finally, the subjects were classified as either under- or nomal weight using the 25th percentile of the DHEW norms as the cutoff point. Procedure Psychiatric patients meeting the chart review inclusion criteria were given the BS, weighed, and had their height measured. Beyond this point, all groups proceeded similarly. After administering the structured interview, subjects completed the EDI, MAC, and BS (if not already completed). The questionnaires were administered in random order. All subjects were paid $10 for their participation. 2Scoring the ED1 results in several subscale scores, and a total score per se is not generated. However. for brevity. the subscale scores were added to form a total score. Because the purpose was to use the ED1 to confirm the clinical diagnosis of an eating disorder, and not to examine subscale differences on the EDI. this seemed appropriate. Readers interested in results for the individual ED1 subscales are invited to write the author. 3Copies of the ?vl.AC, scoring criteria, and an IBM scoring program are available by writing the author.
286
J. SCOTT
MIZES
Table I, Means and standard deviations for eating disorder and selection variables for bulimcs, anorectics. and psychiatric controls Variable Binges/uk’ Vomiting/wk Weight (Ibs) EDI (total) Binge scale
Bulimics 9.5 8.8 128.2 97.7 34.4
(8.0) (9.2) ( 18.0)“b (37.3)” (8.7)
Anorectics 3.5 6.6 107.6 69.5 23.6
(6.9) ( I I .9)‘b (23.9)b (31.7) (7.8)
Controls 0 (0)” 0 (OP 13’.7(21.5) 19.1 (I 1.9) 3.7 (2.7)
~Vorc. hleans in rows vvith like superscripts are not significantly different. ‘Numbers in parentheses are standard deviations.
RESULTS
Several variables were examined via one-way ANOVAs to confirm group assignment, as well as to confirm equivalence on other relevant variables. Means, standard deviations, and planned pairwise comparisons @ I .05) are presented in Table 1. The groups differed significantly on self-reported binges per week, F(2,3 1) = 7.6, p = .002. Bulimics had significantly more binges than either anorectics or controls, both who did not differ from each other. The groups differed significantly on self-reported vomiting episodes per week, F(2, 31) = 3.6, p = .04. Though bulimics and anorectics did not differ from each other, only bulimics vomited more than controls. Weight was significantly different, F(2,3 1) = 3.8, p = .03. Anorectics weighed significantly less than controls, although the anorectics showed a trend (p = .07) toward weighing less than the bulimics. Regarding relative weight classification, all of the anorectics were underweight, all of the psychiatric controls were normal weight, and all but one of the bulimics were normal weight. The overall difference was significant, F(2, 31) = 94.4, p < .OOl. Both bulimics and controls had a significantly higher relative weight classification than anorectics, though they did not differ from each other. EDI total scores were significantly different, F(2, 3 1) = 2 1.9, p < .OOl. Both anorectics and bulimics scored higher than controls. Finally, the groups differed significantly on the BS, F(2.3 1) = 59.8, p < .OO1. Bulimics scored higher than anorectics, both of which scored higher than controls. The groups did not differ on age, M = 22.4, SD = 6.9, F(2, 31) = 1.3,~ = .28; normative ideal weight, A4 = 136.2 lbs, SD = 20.5, F(2, 31) = .36, p = .70: or height, M = 64.9 inches, SD = 4.1, F(2, 31) = .26, p = .77. MAC means and standard deviations for the three study groups are presented in Table 2. For the total score, the one way analysis of variance was significant, F(2, 3 1) = 36.8, p < .OO1, multiple R' = .70. The groups were significanly different on the Rigid Weight Regulation subscale, F(2,3 1) = 38.6, a < .OOI, multiple R* = .7 1. For the SelfControl scale, the effect was also significnat, F(2, 3 1) = 38.3, p < .OOl, multiple RZ = .7 I. Finally, for the Approval subscale, a significant effect was found, F(2, 3 1) = 5.4, P = .009, multiple R' = .26. Planned comparisons for all four scores revealed that both bulimics and anorectics scored significantly higher than controls, though they did not differ from each other. The MAC total scores and subscales were correlated with the EDI total score and subscales for the total sample.4 For the MAC total score, the correlation with the ED1 4Readers author.
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for the individual
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Table 2. Total MAC and subscale means and standard deviations for bulimics. anorectics, and psychiatric controls Bulimics Total’ U’gt. Reduction Self-Control Wgt. & Approval
119.5 (20.5) 73.0 (14.1) 26. I (2.7) 20.4 (5.8)
Anorectics 115.6 (14.7) 71.3 (9.7) 25.8 (2.7) 18.6 (5.3)
Controls 65.1 (12.3) 35.0 (8.7) 16.4 (3.5) 13.7 (3.9)
.Vote. For all comparisons. bulimicsdid not differ from anorectics. though both differed from controls. ‘Numbers in parentheses are standard deviations.
total score was .80, p < .OO1. Correlations with the subscales ranged from .42-.84, and all were significant. The Self-Control subscale correlated significantly with the total EDI, r = .78, p < .OOl. Correlations with ED1 subscales ranged from .38-.80, and all were significant. Rigid Weight Regulation correlated significantly with the Total EDI, r = .79, p < .OOl, and subscale correlations ranged from .41-.86 (all significant). Finally, the Approval subscale correlated with the total EDI, r = .56, p = .OOl. Correlations with ED1 subscales ranged from .28-.60, and all but two were significant. The two non-significant correlations were for the ED1 Perfectionism and Interpersonal Distrust subscales. DISCUSSION
Results ofthe present study further support the criterion-related validity ofthe MAC. Despite the small sample size necessitated by the difficulties of recruiting clinical samples according to strict criteria, large differences were found between the eating disorder groups and a psychiatric comparison group. These results replicate previous findings with bulimic patients, and extend the demonstration of criterion-related validity to anorectics. While the cognitive distortions hypothesized to be relevant to bulimia and anorexia are very similar, it is nonetheless important to demonstrate the MAC’s validity in both populations. Additionally, this is the first time the criterion-related validity of the MAC’s subscales had been assessed in a clinical population. As in previous research, the MAC showed good concurrent validity, this time with reference to the EDI. However, the Weight and Approval subscale appeared to be less strongly associated with the ED1 than were the other two subscales. As in previous research, the MAC accounted for a substantial portion of the between groups variance. In this study, the MAC accounted for 70% of the variance, in Mizes ( 1988) 60%. Thus, the cognitions assessed by the MAC appear to be a prominent feature of anorexia and bulimia. Also, by using a psychiatric control group, this study suggests that the cognitions assessed by the MAC do not appear to be merely reflective of general psychopathology. Rather, they reflect the specific psychopathology of bulimia and anorexia. Although other clinical or nonclinical groups (such as the obese) who have weight-related concerns may endorse these congitions to some extent (see Mizes & Klesges, 1989), it is suggested that the most extreme endorsement of these cognitions is associated with clinical bulimia and anorexia nervosa. Of course, this requires direct empirical investigation.
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A secondary purpose of the study was to conduct a preliminary assessment of potential differences between anorectics and bulimics on the MAC. Though no specific prediction was made. it is interesting that bulimics and anorectics did not dilfer on MAC scores. Thus, the current findings do not shed any light on differences between anorexia and bulimia nervosa. Perhaps this is inherently a difficult discrimination because a substantial portion of patients shift back and forth between the two diagnostic entities. and because of inadequacies in the diagnostic criteria (Mizes, in press). Indeed, various theorists have articulated essentially similar cognitive distortions for the two disorders (i.e.. Fairburn & Garner, 1986). Alternatively, it is also possible that the MAC does not assess psychological constructs which discriminate anorexia and bulimia. Also, it must be acknowledged that the small sample size may have made it difficult to detect small. though real, differences due to low statistical povver. Hovvever. inspection of bulimics’ and anorectics’ MAC means does not even suggest a trend toward a statistically significant difference. The group differences were not even one-fourth ofthe sample standard deviations in most cases. To put this into perspective, a power analysis reveals that 140- 180 bulimics. and an equal number of anorectics would be needed to detect a significant difference for an effect this small, with power set at a conventional .80 (Cohen, 1977). The practical difficulties of recruiting that many eating disorder patients is obvious. Also, the clinical meaningfulness of a difference that small can be questioned. Though the body of research supporting the validity and reliability of the IMAC is growing, further research is clearly warranted. Research on large samples of bulimic and anorectic patients to further examine component structure and reliability would be useful. It is also important to compare bulimics and anorectics to others with eating-related concerns, such as the obese, restrained eaters, and subclinical bingers. In addition to helping establish the discriminant validity with subclinical or alternate forms of eating pathology, this may highlight differences in the psychopathology of the various eating pathology groups. Finally, it will be important to assess the MAC’s validity using in vivo assessment of cognitions as the criterion. REFERENCES American Psychiatric Association. (1987). Diagnosfic und sroris~ical rnanwl ql’~rrwra/ drsorders (3rd ed.). Washington. DC: Author. Cohen 1. ( 1977). Power ana/j,sisfor rhc behavioralsciences (revised cdirionj. Nem j’ork: Academic Press. Department of Health. Education. and Welfare. (1979). W’eighr by hc>ighr and agejitr adrrlrs 18-74 j‘ears LT..% 197/-19i4 (DHEW Publication No. 79-1656, Series I I. No. 280). Bethesda, MD: Author. Fairburn, C. G. (1985). A cognitive behavioral treatment ofbulimia. In D. M. Garner& P. E. Gartinkel (Eds.). Handbook c!Tps?rltoiherup?.for anore.uia nervosa and bulimia (pp. I63- 197). Sew York: Guilford. Fairburn. C. G., 6r Garner, D. M. ( 1986). The diagnosis of bulimia nen’osa. It~tc~rtfariotzalJoltrnal cft5zritz.q Disorders,
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D. M.. 8: Bemis K. M. (1982). A cognitive behavioral approach to anorexia nervosa. Cogniiiw Therapj, and Research. 6, I23- 150. Garner, D. M.. 8: Gariinkel, P. E. (1979). The Eating Attitudes Test: An index ofthe symptoms ofanorexia nervosa. Psj,chologicalMedicine. 9, 273-279. Garner. D. M.. & Olmstead. M. P. (I 981). Earing Disorder Inventor! ttmt~uul. Odessa, FL: Psychological Assessment Resources, Inc. Cormally. 1.. Black, S.. Daston, S.. & Rardin. D. (1982). The assessment ofbinge eating severity among obese persons. Addicliw Behaviors, 7,47-55. Mizes, J. S. (1985). Bulimia: A review of its symptomatology and treatment. .-ld\wtws in Behuvirv Resenrch and Therapy.
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