Unique Contributions of Individual Eating Disorder Symptoms to Eating Disorder-Related Impairment Hovrud Lindsey, De Young Kyle PII: DOI: Reference:
S1471-0153(15)00054-9 doi: 10.1016/j.eatbeh.2015.05.001 EATBEH 930
To appear in:
Eating Behaviors
Received date: Revised date: Accepted date:
7 August 2014 17 February 2015 13 May 2015
Please cite this article as: Lindsey, H. & Kyle, D.Y., Unique Contributions of Individual Eating Disorder Symptoms to Eating Disorder-Related Impairment, Eating Behaviors (2015), doi: 10.1016/j.eatbeh.2015.05.001
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UNIQUE CONTRIBUTION OF EATING DISORDER SYMPTOMS
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Unique Contributions of Individual Eating Disorder Symptoms to Eating
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Disorder-Related Impairment
Lindsey Hovrud, B.S., & Kyle De Young, Ph.D.
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Department of Psychology, University of North Dakota
Corresponding author:
Kyle De Young, Ph.D.
Assistant Professor of Psychology 319 Harvard Street Stop 8380 Grand Forks, ND 58202-8380 [email protected] Ph: (701) 777-5671
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Abstract This study examined the unique contribution of individual eating disorder symptoms and related
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features to overall eating disorder-related impairment. Participants (N=113) from the community
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with eating disorders completed assessments including the Clinical Impairment Assessment (CIA) and the Eating Disorder Examination Questionnaire. A multiple linear regression analysis
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indicated that 58.6% of variance in the CIA was accounted for by binge eating frequency, weight
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and shape concerns, and depression. These findings indicate that certain eating disorder symptoms uniquely account for impairment, and that depression is a substantial contributor. It is
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possible that purging, restrictive eating, and body mass index did not significantly contribute to impairment because these features are consistent with many individuals’ weight and shape goals.
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The results imply that eating disorder-related impairment may be more a result of cognitive features and binge eating rather than body weight and compensatory behaviors.
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Keywords: eating disorders, impairment, binge eating, weight and shape concerns, depression
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1. Introduction Eating disorders (EDs) are an important and growing health burden, as indicated by a
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38% increase in disability-adjusted life years (i.e., the amount of years lost due to non-fatal
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illness or impairment) between 1990 and 2010 (Murray et al., 2012). EDs also create substantial annual costs ranging from $1,288 to $8,042 per patient depending on the type of intervention and
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therapeutic techniques utilized, although this number may underestimate their economic burden
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(Stuhldreher et al, 2012). In addition, EDs are associated with a near fivefold risk of suicide attempts requiring hospitalization compared to general population controls (Suokas et al., 2014).
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Another method of quantifying the impact of these disorders is to measure their subjective impairment on quality of life (QoL). This includes an indication of individuals’
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perception of their ability to carry out everyday activities such as physical functioning, role limitations due to personal, emotional, or physical health problems, emotional well-being, and
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social functioning (Ware & Sherbourne, 1992). Quantification of the impact of EDs on individuals’ lives is important for appreciating the consequences of the disorders themselves and informing the public and funding institutions, whose advocacy and support may improve treatment and management of these disorders. On broad measures of QoL, individuals with EDs, recruited from the community, report more impairment than controls without EDs (Cook & Hausenblas, 2011). Furthermore, there are varying degrees of impairment in QoL between the EDs. Generally, individuals with anorexia nervosa (AN) report worse overall QoL compared to individuals with bulimia nervosa (BN) and eating disorder not otherwise specified (EDNOS; Abraham et al., 2006; Bamford & Sly, 2010). However, individuals with the restrictive subtype of AN have also been found to report comparable QoL to control subjects (Mond et al., 2005; Doll et al., 2005). Notably, these
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findings were generated using a general measure of QoL rather than an ED-specific measure. Such findings may support Mond and colleague’s (2005) assertion that “reliance on any one
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instrument is likely to be misleading in assessing the quality of life of ED patients” (p. 177). In
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further support, ED-specific measures of QoL appear more sensitive to differences in QoL between individuals with EDs and clinical controls than measures of general QoL, which may
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miss important aspects of the impact of these disorders on people’s lives (Ackard el al., 2014).
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Although ED diagnoses are exclusive of one another (American Psychiatric Association, 2013), they share common behavioral and psychological features that may include binge eating,
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compensatory behaviors such as purging, restrictive eating behaviors, and undue influence of weight and shape concerns on self-evaluation, which has led some to suggest they share core
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psychopathology (Fairburn et al., 2003). Additionally, approximately 75% of individuals presenting with EDs do not meet formal diagnostic criteria for an ED (Le Grange et al., 2012). It
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is therefore important to understand how ED symptoms individually affect impairment. Such an understanding may explain observed differences in impairment between diagnoses if certain symptoms are more impairing than others (e.g., very low body weight compared to binge eating), or are more common in (or exclusive to) certain diagnoses. This information will also increase our understanding of impairment due to ED symptoms in individuals who present with EDs that do not meet formal diagnostic criteria. Only limited research exists to address these issues. One study examined the impact of binge eating, dietary restriction, purging, and overvaluation of body weight or shape on QoL in men and women and found that binge eating was associated with greater health impairment in men, whereas overvaluation of weight and shape had a greater impact on impairment in women (Mitchison et al., 2013). Another study found that individuals with binge-eating disorder (BED)
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who reported extreme weight and shape concerns had significantly higher levels of psychosocial impairment than those without extreme weight and shape concerns, indicating the impact of
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weight and shape concerns on impairment (Mond et al., 2007). Together these findings suggest
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that individual ED symptoms may contribute to QoL impairment differently and quantifying their individual impact will clarify the source of the burden on those affected.
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No studies have yet quantified individual symptoms’ unique contribution to QoL
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impairment, which is critical because these symptoms typically co-occur and do so in a number of different patterns. By understanding their individual contributions to impairment, treatments
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may be directed toward alleviating the most direct detrimental symptoms to improve individuals’ lives. The purpose of this study was to examine how ED symptoms and related features uniquely
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contribute to psychosocial impairment using a measure to quantify impairment developed specifically for EDs. We had no priori hypotheses about which symptoms in particular may
2. Method
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relate most strongly with impairment.
2.1 Participants
Participants (N=113) were men (n=21) and women (n=92) recruited from a northeastern city in the United States using flyers and from around the country using Craigslist.org who reported clinically significant eating pathology. Three participants discontinued their participation before completing the first study procedure (2 men and 1 woman), and they are not included in any of the following information. Participants ranged in age ranged from 18 to 62 years and had a mean (SD) age of 32.68 (12.23) years. With regards to ethnicity, 71.8% selfidentified as Caucasian, 9.1% as Asian/Pacific Islander, 8.2% as Black/African American, 7.3%
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as Hispanic, 0.9% as Native American, 1.8% indicated other/mixed, and 0.9% did not provide this information.
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Inclusion criteria included being at least 18 years of age and having clinically significant eating pathology as indicated by at least one of the following: (1) low body weight (i.e., body
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mass index < 18kg/m2) and undue influence of body weight or shape on self-evaluation; (2)
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purging (i.e., self-induced vomiting, laxative, diuretic, or enema misuse, or the abuse of
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medication such as insulin) at least once every two weeks over the previous 3 months and undue influence of body weight or shape on self-evaluation or marked distress about purging; (3) binge
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eating episodes at least once per week over the previous 3 months and undue influence of body weight or shape on self-evaluation or marked distress about binge eating. Table 1 details the
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percent of participants who met each of these inclusion criteria, as assessed by the Eating Disorder Diagnostic Scale (EDDS; Stice et al., 2000). Eight participants met only inclusion
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criterion 1, thirty-one met only criterion 2, and ten participants met only inclusion criterion 3. Fifty-four participants met both criteria 2 and 3, four met criteria 1 and 3, and six participants met all three criteria. No participants met both criteria 1 and 2 without also meeting criterion 3. 2.2 Measures
The Clinical Impairment Assessment (CIA; Bohn & Fairburn, 2008) is a 16-item selfreport measure of the severity of impairment due to ED symptoms that focuses on the aspects of life typically affected by ED pathology: mood and self-perception, cognitive functioning, interpersonal functioning, and work performance. The CIA was utilized to capture ED specific impairment. The Eating Disorder Examination Questionnaire (EDE-Q; Fairburn & Beglin, 1994) is a self-report measure that focuses on the main cognitive and behavioral features of EDs (e.g.,
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assesses the frequency at which individuals engaged in certain ED behaviors over the previous 28 days) and includes four subscales: dietary restraint, eating concern, shape concern, and weight
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concern. In the present study, it was used to determine binge eating and purging episode
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frequency over the preceding 28 days.
The EDDS was utilized to screen participants for eligibility via telephone, assessing
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study inclusion criteria. The EDDS is a 22-item self-report questionnaire that assesses ED
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psychopathology consistent with the DSM-IV-TR (APA, 2000), and is highly specific and sensitive for this purpose (Anderson et al., 2009; Krabbenborg et al., 2012). Two items on this
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measure assess the importance of body weight and shape on self-evaluation. Participants were deemed to have satisfied the inclusion criterion of undue influence of weight and shape on self-
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evaluation if they rated themselves at least a “4” on one of these 7-point scales. Two supplemental items were added to this scale for the present study to assess the magnitude of
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distress over the presence of purging behaviors and binge eating separately on a 7-point scale from “not at all distressed” to “extremely distressed”. Participants were deemed to have indicated marked distress regarding binge eating or purging if they indicated they were at least a “4” on these 7-point scales.
The Multidimensional Assessment of Eating Disorder Symptoms (MAEDS; Anderson et al., 1999) is a reliable and valid self-report inventory that measures six symptom domains related to eating disorders: binge eating, restrictive eating, purgative behavior, fear of fatness, avoidance of forbidden foods, and depression. This inventory was used to determine participants’ fear of fatness, dietary restriction, and depression. 2.3 Procedure
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Individuals interested in participating (N = 139) were screened via telephone using the EDDS to determine eligibility. Eligible participants (n = 113) then completed various self-report
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questionnaires including the CIA and EDE-Q over the Internet over the course of 12 weeks.
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They completed a baseline assessment and a 6- and 12-week follow-up. In addition, they completed brief symptom frequency and mood assessments weekly during the 12 weeks that are
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not included in the present study (see De Young et al., 2014 for more details). Participants were
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compensated $40 for completing all assessments. These procedures were approved by the Institutional Review Board at the University at Albany, State University of New York.
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2.4 Statistical Analysis
A two-step multiple linear regression analysis was used to accomplish the aim of this
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study with baseline impairment as measured by the CIA as the dependent variable. Baseline body mass index (BMI) calculated from self-reported height and weight, weight and shape
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concerns, purging (self-induced vomiting plus laxative misuse due to the low base rate of laxative misuse) and binge eating frequencies over the previous 28 days as measured by the EDE-Q, and the fear of fatness and dietary restriction scales from the MAEDS were entered as the primary independent variables. Due to positive skew, BMI, binge eating frequency, and purging frequency were all square root-transformed to approximate normal distributions. Due to a high inter-correlation (i.e., Pearson r = .88), EDE-Q weight concern and EDE-Q shape concern were averaged together to create an aggregate weight/shape concern variable. Next, gender, age, and the MAEDS depression scale were added to the model to control for the possibility that men or women might be more impaired than the other, or be more likely to report higher levels of certain symptoms, that age may be related to impairment, and the possibility that depression would predict both impairment and eating disorder symptoms. These variables were added in a
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second step to determine the amount of variance related exclusively to ED symptoms and then to quantify the impact of the covariates. An additional model was run after mean-centering and
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taking the absolute value of BMI to test whether impairment was related to lower and higher
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BMIs versus mid-range BMIs. Statistical significance was set at the conventional level of p < .05 for model parameters.
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3. Results
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Participants reported a mean (SD; minimum, maximum) of 15.19 (17.03; 0, 101) binge eating and 13.74 (21.31; 0, 112) purging episodes over the past 28 days and a BMI of 26.15
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(9.38; 14.70, 78.37) kg/m2. The mean (SD) CIA score was 28.62 (11.98), and 83.7% of the sample scored above the recommended cutoff for clinical impairment (Bohn et al., 2008). These
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means and ranges indicate that the sample represents a group of individuals with clinically significant eating problems with a range of symptom presentations.
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The first step of the regression analysis accounted for a total of 46.0% of variance in impairment (F(6, 102) = 16.33, p < .001), and weight and shape concerns (β = .455, t = 4.35, p < .001), binge eating frequency (β = .286, t = 3.51, p < .001), and dietary restriction (β = .193, t = 2.17, p = .033) were all unique and positive predictors of impairment. BMI, purging frequency, and fear of fatness were not unique predictors. In the second step, depression, gender, and age were added, and the new model accounted for 58.6% (F(9, 99) = 17.98, p < .001) of total variance in impairment. The details of the model parameters are displayed in Table 2. Weight and shape concerns and binge eating frequency remained significant unique predictors of impairment. Restrictive eating was no longer a unique predictor. It appears as though the relationship between restrictive eating and impairment is
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accounted for by gender, age, and/or depression. Gender and age did not uniquely contribute to the prediction of impairment, but depression was a significant positive predictor.
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Changing the scale of BMI by mean-centering and taking the absolute value so that higher values represent BMIs further away from the mean did not significantly improve the
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model (ΔR2 = .008, F (1, 99) = 2.22, p = .139) or result in BMI accounting for significant unique
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variance (β = .096, t = 1.49, p = .139). As a result, the previous model was retained.
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To quantify the size of the effect for the significant unique predictors of impairment (i.e., binge eating, weight and shape concerns, and depression), all non-significant predictors were
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first removed. The total variance accounted for by this modified model was 57.1%, which was not significantly different than the full model at 58.6% (ΔR2 = .037, F (6, 99) = 1.62, p = .149).
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Next, each predictor was removed one at a time to measure the size of its unique contribution to the variance explained. In total, of the 57.1% of variance explained, 34.1% was shared among
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the three predictors, 4.2% was unique to weight and shape, 3.2% was unique to binge eating, and 15.6% was unique to depression.
4. Discussion
The purpose of this study was to compare how individual ED symptoms and related features (i.e. BMI, weight and shape concerns, purging frequency, binge eating frequency, fear of fatness, and restrictive eating) contribute uniquely to overall impairment related to EDs while controlling for age, gender, and depression. The results indicate that approximately half of the variance in impairment can be explained by these features. Specifically, weight and shape concerns, binge eating, and dietary restriction were all unique and positive predictors of impairment. However, after controlling for gender and depression, dietary restriction was no longer a unique predictor.
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These results suggest that the severity and frequency of ED symptoms and related features account for a substantial amount of variability in ED-related impairment, but concerns
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about body weight and shape and binge eating frequency in particular exert the greatest
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influence. It is interesting that purging frequency and dietary restriction were not unique predictors given their often severe and observable nature. However, this may be due to these
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behaviors being consistent with many individuals’ weight and shape goals, therefore causing less
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distress compared to other symptoms. It is possible that fear of fatness and BMI were not contributors because body weight and shape concerns are simply a more efficient index of
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subjective distress about how one feels about his/her body than the size of one’s body or the construct of fear of fatness.
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Although depression is not a criterion for EDs, it commonly co-occurs. In fact, in a nationally representative sample, out of all the mood disorders, major depressive disorder had the
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highest comorbidity with eating disorders, with just under half of respondents meeting diagnostic criteria (Hudson et al., 2007). Thus, it is likely that many individuals in this study experienced clinically significant symptoms of depression, which in itself is impairing. These depressive symptoms may change one’s subjective report of how ED symptoms relate to his/her impairment or make it difficult to disentangle which aspects of impairment result from ED symptoms versus depression symptoms (e.g., ruminations about appearance). Indeed, the measure of eating disorder-related impairment utilized in this study includes items that assess the extent to which eating disorder symptoms affect one’s mood. Strengths of this study include the utilization of a measure specifically designed to assess ED-related impairment. This sample was from the community and was diverse and relatively severe. Although minimum thresholds were required to meet inclusion criteria, criteria could be
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met in a variety of ways. Thus, the full range of severity for each eating disorder feature was represented (e.g., binge eating ranged from a frequency of 0 to 101 episodes in the previous
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month). Nevertheless, the findings of this study should be interpreted within the context of its
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limitations. Although the EDDS has been supported by a number of studies, its performance may be altered by administration over the telephone. Treatment-seeking status of the participants was
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not assessed, so it is unknown to what extent this sample is representative of individuals with
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EDs presenting for treatment. Duration of illness was also not assessed, so it was not available to include in the model. It is possible the contribution of individual eating disorder features to
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impairment varies over the course of the illness. Additionally, because the measures relied on self-report, it is possible that participants did not accurately report the frequency of their ED
the severity of these features.
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behaviors (i.e. purging and binge eating) resulting in the introduction of error to the estimates of
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Future research should continue to evaluate the effects of individual ED symptoms on impairment to better understand the specific way in which ED features affect the lives of those who have them. Understanding this impairment is essential given the high mortality risk and economic burden these disorders pose. The results of the current study highlight the importance of how individual ED features contribute to ED-related impairment and suggest that interventions reducing binge eating frequency and concerns about body shape and weight may be the most beneficial for favorably impacting impairment. The results also highlight the importance of depressed mood in its relationship with impairment in EDs. Future research should test whether improvements in these areas indeed result in less impairment than improvement in other domains so the alleviation of impairment can be effectively targeted in treatment.
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Table 1 Descriptive of Participants Meeting Inclusion Criteria by Eating Disorder Symptom
SD
Min
26.15
9.38
14.7
Weight Concerns
5.15
1.2
0
15.9
0
6
6.86
0
35
1.62
0
10
0
32.5
1.08
Self-Induced Vomiting/Week
4.06 0.71
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5.13
5.67
78.37 6
Shape Concerns
Laxative Misuse/Week Binge Eating/Week
Max
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Body Mass Index
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M
% Meeting Criterion Threshold
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Parameter
6.17
94.7*
66.4*
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*Merged to represent weight and shape concerns and purging frequency, respectively.
80.5
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Table 2 Linear Regression Results Accounting for Impairment due to Eating Disorder Symptoms β
p
Lower 95% CI
Upper 95% CI
-2.96
1.97
1.21
9.57
-0.94
0.46
0.76
2.54
-0.03
-0.40
.689
Weight/Shape Concerns
0.25
2.56
.012
Purging Frequency*
-0.05
-0.69
Binge Eating Frequency*
0.26
Fear of Fatness
-0.03
-0.33
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.741
-0.18
0.13
Restrictive Eating
0.09
1.12
.266
-0.06
0.23
0.72
.471
-2.58
5.53
-0.14
-1.95
.054
-0.28
0.002
5.31
S1471-0153(15)00054-9 doi: 10.1016/j.eatbeh.2015.05.001 EATBEH 930
To appear in:
Eating Behaviors
Received date: Revised date: Accepted date:
7 August 2014 17 February 2015 13 May 2015
Please cite this article as: Lindsey, H. & Kyle, D.Y., Unique Contributions of Individual Eating Disorder Symptoms to Eating Disorder-Related Impairment, Eating Behaviors (2015), doi: 10.1016/j.eatbeh.2015.05.001
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UNIQUE CONTRIBUTION OF EATING DISORDER SYMPTOMS
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Unique Contributions of Individual Eating Disorder Symptoms to Eating
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Disorder-Related Impairment
Lindsey Hovrud, B.S., & Kyle De Young, Ph.D.
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Department of Psychology, University of North Dakota
Corresponding author:
Kyle De Young, Ph.D.
Assistant Professor of Psychology 319 Harvard Street Stop 8380 Grand Forks, ND 58202-8380 [email protected] Ph: (701) 777-5671
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Abstract This study examined the unique contribution of individual eating disorder symptoms and related
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features to overall eating disorder-related impairment. Participants (N=113) from the community
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with eating disorders completed assessments including the Clinical Impairment Assessment (CIA) and the Eating Disorder Examination Questionnaire. A multiple linear regression analysis
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indicated that 58.6% of variance in the CIA was accounted for by binge eating frequency, weight
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and shape concerns, and depression. These findings indicate that certain eating disorder symptoms uniquely account for impairment, and that depression is a substantial contributor. It is
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possible that purging, restrictive eating, and body mass index did not significantly contribute to impairment because these features are consistent with many individuals’ weight and shape goals.
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The results imply that eating disorder-related impairment may be more a result of cognitive features and binge eating rather than body weight and compensatory behaviors.
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Keywords: eating disorders, impairment, binge eating, weight and shape concerns, depression
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1. Introduction Eating disorders (EDs) are an important and growing health burden, as indicated by a
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38% increase in disability-adjusted life years (i.e., the amount of years lost due to non-fatal
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illness or impairment) between 1990 and 2010 (Murray et al., 2012). EDs also create substantial annual costs ranging from $1,288 to $8,042 per patient depending on the type of intervention and
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therapeutic techniques utilized, although this number may underestimate their economic burden
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(Stuhldreher et al, 2012). In addition, EDs are associated with a near fivefold risk of suicide attempts requiring hospitalization compared to general population controls (Suokas et al., 2014).
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Another method of quantifying the impact of these disorders is to measure their subjective impairment on quality of life (QoL). This includes an indication of individuals’
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perception of their ability to carry out everyday activities such as physical functioning, role limitations due to personal, emotional, or physical health problems, emotional well-being, and
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social functioning (Ware & Sherbourne, 1992). Quantification of the impact of EDs on individuals’ lives is important for appreciating the consequences of the disorders themselves and informing the public and funding institutions, whose advocacy and support may improve treatment and management of these disorders. On broad measures of QoL, individuals with EDs, recruited from the community, report more impairment than controls without EDs (Cook & Hausenblas, 2011). Furthermore, there are varying degrees of impairment in QoL between the EDs. Generally, individuals with anorexia nervosa (AN) report worse overall QoL compared to individuals with bulimia nervosa (BN) and eating disorder not otherwise specified (EDNOS; Abraham et al., 2006; Bamford & Sly, 2010). However, individuals with the restrictive subtype of AN have also been found to report comparable QoL to control subjects (Mond et al., 2005; Doll et al., 2005). Notably, these
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findings were generated using a general measure of QoL rather than an ED-specific measure. Such findings may support Mond and colleague’s (2005) assertion that “reliance on any one
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instrument is likely to be misleading in assessing the quality of life of ED patients” (p. 177). In
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further support, ED-specific measures of QoL appear more sensitive to differences in QoL between individuals with EDs and clinical controls than measures of general QoL, which may
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miss important aspects of the impact of these disorders on people’s lives (Ackard el al., 2014).
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Although ED diagnoses are exclusive of one another (American Psychiatric Association, 2013), they share common behavioral and psychological features that may include binge eating,
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compensatory behaviors such as purging, restrictive eating behaviors, and undue influence of weight and shape concerns on self-evaluation, which has led some to suggest they share core
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psychopathology (Fairburn et al., 2003). Additionally, approximately 75% of individuals presenting with EDs do not meet formal diagnostic criteria for an ED (Le Grange et al., 2012). It
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is therefore important to understand how ED symptoms individually affect impairment. Such an understanding may explain observed differences in impairment between diagnoses if certain symptoms are more impairing than others (e.g., very low body weight compared to binge eating), or are more common in (or exclusive to) certain diagnoses. This information will also increase our understanding of impairment due to ED symptoms in individuals who present with EDs that do not meet formal diagnostic criteria. Only limited research exists to address these issues. One study examined the impact of binge eating, dietary restriction, purging, and overvaluation of body weight or shape on QoL in men and women and found that binge eating was associated with greater health impairment in men, whereas overvaluation of weight and shape had a greater impact on impairment in women (Mitchison et al., 2013). Another study found that individuals with binge-eating disorder (BED)
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who reported extreme weight and shape concerns had significantly higher levels of psychosocial impairment than those without extreme weight and shape concerns, indicating the impact of
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weight and shape concerns on impairment (Mond et al., 2007). Together these findings suggest
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that individual ED symptoms may contribute to QoL impairment differently and quantifying their individual impact will clarify the source of the burden on those affected.
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No studies have yet quantified individual symptoms’ unique contribution to QoL
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impairment, which is critical because these symptoms typically co-occur and do so in a number of different patterns. By understanding their individual contributions to impairment, treatments
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may be directed toward alleviating the most direct detrimental symptoms to improve individuals’ lives. The purpose of this study was to examine how ED symptoms and related features uniquely
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contribute to psychosocial impairment using a measure to quantify impairment developed specifically for EDs. We had no priori hypotheses about which symptoms in particular may
2. Method
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relate most strongly with impairment.
2.1 Participants
Participants (N=113) were men (n=21) and women (n=92) recruited from a northeastern city in the United States using flyers and from around the country using Craigslist.org who reported clinically significant eating pathology. Three participants discontinued their participation before completing the first study procedure (2 men and 1 woman), and they are not included in any of the following information. Participants ranged in age ranged from 18 to 62 years and had a mean (SD) age of 32.68 (12.23) years. With regards to ethnicity, 71.8% selfidentified as Caucasian, 9.1% as Asian/Pacific Islander, 8.2% as Black/African American, 7.3%
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as Hispanic, 0.9% as Native American, 1.8% indicated other/mixed, and 0.9% did not provide this information.
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Inclusion criteria included being at least 18 years of age and having clinically significant eating pathology as indicated by at least one of the following: (1) low body weight (i.e., body
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mass index < 18kg/m2) and undue influence of body weight or shape on self-evaluation; (2)
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purging (i.e., self-induced vomiting, laxative, diuretic, or enema misuse, or the abuse of
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medication such as insulin) at least once every two weeks over the previous 3 months and undue influence of body weight or shape on self-evaluation or marked distress about purging; (3) binge
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eating episodes at least once per week over the previous 3 months and undue influence of body weight or shape on self-evaluation or marked distress about binge eating. Table 1 details the
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percent of participants who met each of these inclusion criteria, as assessed by the Eating Disorder Diagnostic Scale (EDDS; Stice et al., 2000). Eight participants met only inclusion
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criterion 1, thirty-one met only criterion 2, and ten participants met only inclusion criterion 3. Fifty-four participants met both criteria 2 and 3, four met criteria 1 and 3, and six participants met all three criteria. No participants met both criteria 1 and 2 without also meeting criterion 3. 2.2 Measures
The Clinical Impairment Assessment (CIA; Bohn & Fairburn, 2008) is a 16-item selfreport measure of the severity of impairment due to ED symptoms that focuses on the aspects of life typically affected by ED pathology: mood and self-perception, cognitive functioning, interpersonal functioning, and work performance. The CIA was utilized to capture ED specific impairment. The Eating Disorder Examination Questionnaire (EDE-Q; Fairburn & Beglin, 1994) is a self-report measure that focuses on the main cognitive and behavioral features of EDs (e.g.,
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assesses the frequency at which individuals engaged in certain ED behaviors over the previous 28 days) and includes four subscales: dietary restraint, eating concern, shape concern, and weight
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concern. In the present study, it was used to determine binge eating and purging episode
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frequency over the preceding 28 days.
The EDDS was utilized to screen participants for eligibility via telephone, assessing
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study inclusion criteria. The EDDS is a 22-item self-report questionnaire that assesses ED
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psychopathology consistent with the DSM-IV-TR (APA, 2000), and is highly specific and sensitive for this purpose (Anderson et al., 2009; Krabbenborg et al., 2012). Two items on this
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measure assess the importance of body weight and shape on self-evaluation. Participants were deemed to have satisfied the inclusion criterion of undue influence of weight and shape on self-
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evaluation if they rated themselves at least a “4” on one of these 7-point scales. Two supplemental items were added to this scale for the present study to assess the magnitude of
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distress over the presence of purging behaviors and binge eating separately on a 7-point scale from “not at all distressed” to “extremely distressed”. Participants were deemed to have indicated marked distress regarding binge eating or purging if they indicated they were at least a “4” on these 7-point scales.
The Multidimensional Assessment of Eating Disorder Symptoms (MAEDS; Anderson et al., 1999) is a reliable and valid self-report inventory that measures six symptom domains related to eating disorders: binge eating, restrictive eating, purgative behavior, fear of fatness, avoidance of forbidden foods, and depression. This inventory was used to determine participants’ fear of fatness, dietary restriction, and depression. 2.3 Procedure
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Individuals interested in participating (N = 139) were screened via telephone using the EDDS to determine eligibility. Eligible participants (n = 113) then completed various self-report
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questionnaires including the CIA and EDE-Q over the Internet over the course of 12 weeks.
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They completed a baseline assessment and a 6- and 12-week follow-up. In addition, they completed brief symptom frequency and mood assessments weekly during the 12 weeks that are
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not included in the present study (see De Young et al., 2014 for more details). Participants were
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compensated $40 for completing all assessments. These procedures were approved by the Institutional Review Board at the University at Albany, State University of New York.
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2.4 Statistical Analysis
A two-step multiple linear regression analysis was used to accomplish the aim of this
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study with baseline impairment as measured by the CIA as the dependent variable. Baseline body mass index (BMI) calculated from self-reported height and weight, weight and shape
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concerns, purging (self-induced vomiting plus laxative misuse due to the low base rate of laxative misuse) and binge eating frequencies over the previous 28 days as measured by the EDE-Q, and the fear of fatness and dietary restriction scales from the MAEDS were entered as the primary independent variables. Due to positive skew, BMI, binge eating frequency, and purging frequency were all square root-transformed to approximate normal distributions. Due to a high inter-correlation (i.e., Pearson r = .88), EDE-Q weight concern and EDE-Q shape concern were averaged together to create an aggregate weight/shape concern variable. Next, gender, age, and the MAEDS depression scale were added to the model to control for the possibility that men or women might be more impaired than the other, or be more likely to report higher levels of certain symptoms, that age may be related to impairment, and the possibility that depression would predict both impairment and eating disorder symptoms. These variables were added in a
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second step to determine the amount of variance related exclusively to ED symptoms and then to quantify the impact of the covariates. An additional model was run after mean-centering and
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taking the absolute value of BMI to test whether impairment was related to lower and higher
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BMIs versus mid-range BMIs. Statistical significance was set at the conventional level of p < .05 for model parameters.
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3. Results
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Participants reported a mean (SD; minimum, maximum) of 15.19 (17.03; 0, 101) binge eating and 13.74 (21.31; 0, 112) purging episodes over the past 28 days and a BMI of 26.15
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(9.38; 14.70, 78.37) kg/m2. The mean (SD) CIA score was 28.62 (11.98), and 83.7% of the sample scored above the recommended cutoff for clinical impairment (Bohn et al., 2008). These
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means and ranges indicate that the sample represents a group of individuals with clinically significant eating problems with a range of symptom presentations.
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The first step of the regression analysis accounted for a total of 46.0% of variance in impairment (F(6, 102) = 16.33, p < .001), and weight and shape concerns (β = .455, t = 4.35, p < .001), binge eating frequency (β = .286, t = 3.51, p < .001), and dietary restriction (β = .193, t = 2.17, p = .033) were all unique and positive predictors of impairment. BMI, purging frequency, and fear of fatness were not unique predictors. In the second step, depression, gender, and age were added, and the new model accounted for 58.6% (F(9, 99) = 17.98, p < .001) of total variance in impairment. The details of the model parameters are displayed in Table 2. Weight and shape concerns and binge eating frequency remained significant unique predictors of impairment. Restrictive eating was no longer a unique predictor. It appears as though the relationship between restrictive eating and impairment is
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accounted for by gender, age, and/or depression. Gender and age did not uniquely contribute to the prediction of impairment, but depression was a significant positive predictor.
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Changing the scale of BMI by mean-centering and taking the absolute value so that higher values represent BMIs further away from the mean did not significantly improve the
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model (ΔR2 = .008, F (1, 99) = 2.22, p = .139) or result in BMI accounting for significant unique
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variance (β = .096, t = 1.49, p = .139). As a result, the previous model was retained.
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To quantify the size of the effect for the significant unique predictors of impairment (i.e., binge eating, weight and shape concerns, and depression), all non-significant predictors were
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first removed. The total variance accounted for by this modified model was 57.1%, which was not significantly different than the full model at 58.6% (ΔR2 = .037, F (6, 99) = 1.62, p = .149).
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Next, each predictor was removed one at a time to measure the size of its unique contribution to the variance explained. In total, of the 57.1% of variance explained, 34.1% was shared among
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the three predictors, 4.2% was unique to weight and shape, 3.2% was unique to binge eating, and 15.6% was unique to depression.
4. Discussion
The purpose of this study was to compare how individual ED symptoms and related features (i.e. BMI, weight and shape concerns, purging frequency, binge eating frequency, fear of fatness, and restrictive eating) contribute uniquely to overall impairment related to EDs while controlling for age, gender, and depression. The results indicate that approximately half of the variance in impairment can be explained by these features. Specifically, weight and shape concerns, binge eating, and dietary restriction were all unique and positive predictors of impairment. However, after controlling for gender and depression, dietary restriction was no longer a unique predictor.
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These results suggest that the severity and frequency of ED symptoms and related features account for a substantial amount of variability in ED-related impairment, but concerns
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about body weight and shape and binge eating frequency in particular exert the greatest
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influence. It is interesting that purging frequency and dietary restriction were not unique predictors given their often severe and observable nature. However, this may be due to these
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behaviors being consistent with many individuals’ weight and shape goals, therefore causing less
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distress compared to other symptoms. It is possible that fear of fatness and BMI were not contributors because body weight and shape concerns are simply a more efficient index of
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subjective distress about how one feels about his/her body than the size of one’s body or the construct of fear of fatness.
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Although depression is not a criterion for EDs, it commonly co-occurs. In fact, in a nationally representative sample, out of all the mood disorders, major depressive disorder had the
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highest comorbidity with eating disorders, with just under half of respondents meeting diagnostic criteria (Hudson et al., 2007). Thus, it is likely that many individuals in this study experienced clinically significant symptoms of depression, which in itself is impairing. These depressive symptoms may change one’s subjective report of how ED symptoms relate to his/her impairment or make it difficult to disentangle which aspects of impairment result from ED symptoms versus depression symptoms (e.g., ruminations about appearance). Indeed, the measure of eating disorder-related impairment utilized in this study includes items that assess the extent to which eating disorder symptoms affect one’s mood. Strengths of this study include the utilization of a measure specifically designed to assess ED-related impairment. This sample was from the community and was diverse and relatively severe. Although minimum thresholds were required to meet inclusion criteria, criteria could be
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met in a variety of ways. Thus, the full range of severity for each eating disorder feature was represented (e.g., binge eating ranged from a frequency of 0 to 101 episodes in the previous
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month). Nevertheless, the findings of this study should be interpreted within the context of its
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limitations. Although the EDDS has been supported by a number of studies, its performance may be altered by administration over the telephone. Treatment-seeking status of the participants was
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not assessed, so it is unknown to what extent this sample is representative of individuals with
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EDs presenting for treatment. Duration of illness was also not assessed, so it was not available to include in the model. It is possible the contribution of individual eating disorder features to
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impairment varies over the course of the illness. Additionally, because the measures relied on self-report, it is possible that participants did not accurately report the frequency of their ED
the severity of these features.
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behaviors (i.e. purging and binge eating) resulting in the introduction of error to the estimates of
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Future research should continue to evaluate the effects of individual ED symptoms on impairment to better understand the specific way in which ED features affect the lives of those who have them. Understanding this impairment is essential given the high mortality risk and economic burden these disorders pose. The results of the current study highlight the importance of how individual ED features contribute to ED-related impairment and suggest that interventions reducing binge eating frequency and concerns about body shape and weight may be the most beneficial for favorably impacting impairment. The results also highlight the importance of depressed mood in its relationship with impairment in EDs. Future research should test whether improvements in these areas indeed result in less impairment than improvement in other domains so the alleviation of impairment can be effectively targeted in treatment.
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Table 1 Descriptive of Participants Meeting Inclusion Criteria by Eating Disorder Symptom
SD
Min
26.15
9.38
14.7
Weight Concerns
5.15
1.2
0
15.9
0
6
6.86
0
35
1.62
0
10
0
32.5
1.08
Self-Induced Vomiting/Week
4.06 0.71
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5.13
5.67
78.37 6
Shape Concerns
Laxative Misuse/Week Binge Eating/Week
Max
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Body Mass Index
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% Meeting Criterion Threshold
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Parameter
6.17
94.7*
66.4*
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*Merged to represent weight and shape concerns and purging frequency, respectively.
80.5
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Table 2 Linear Regression Results Accounting for Impairment due to Eating Disorder Symptoms β
p
Lower 95% CI
Upper 95% CI
-2.96
1.97
1.21
9.57
-0.94
0.46
0.76
2.54
-0.03
-0.40
.689
Weight/Shape Concerns
0.25
2.56
.012
Purging Frequency*
-0.05
-0.69
Binge Eating Frequency*
0.26
Fear of Fatness
-0.03
-0.33
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.741
-0.18
0.13
Restrictive Eating
0.09
1.12
.266
-0.06
0.23
0.72
.471
-2.58
5.53
-0.14
-1.95
.054
-0.28
0.002
5.31
