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Defining Purging Disorder in Practice
By Pamela K. Keel, PhD
University of Iowa, Iowa City
Reprinted from Eating Disorders Review
May/June 2008 Volume 19, Number 3
©2008 Gürze Books
In a clinical case series published in 1986 on atypical eating disorders, Mitchell and colleagues described a syndrome among normal-weight individuals that was characterized by self-induced vomiting after eating small amounts of food.1 This syndrome was also included as an example of an eating disorder not otherwise specified (EDNOS) in the Diagnostic and Statistical Manual for Mental Disorders Third Edition-Revised (DSM-III-R) in 1987.2 Although purging disorder was identified 20 years ago, more detailed studies and information about it have only recently emerged.
As described in a recent review of purging disorder,3 studies support the clinical significance of purging disorder as well as its potential distinctiveness from bulimia nervosa-purging subtype. In addition, epidemiologic studies indicate that the prevalence of purging disorder may be comparable to the estimated prevalence of anorexia nervosa (AN) and bulimia nervosa (BN).3 This article focuses on features that describe purging disorder, how its clinical presentation differs from those of AN, BN and binge eating disorder (BED), patterns of comorbidity commonly observed in purging disorder, and treatment considerations.
A Description of Purging Disorder
Because purging disorder has not been specifically delineated within the most recent DSM or in the International Classification of Diseases, there is no officially recognized definition for it. Thus, different studies of the condition have employed different inclusion and exclusion criteria. However, past definitions have all included certain features.
First, individuals with purging disorder regularly use self-induced vomiting, laxatives, diuretics or other extreme methods to control their weight or shape.
Second, individuals with purging disorder are not significantly underweight. Instead, they typically fall within a normal weight range, with a minimum body mass index (BMI) above 18.5 kg/m2 and body weight greater than 85% of that expected for their height and age. Although these patients tend not to be overweight, they may have a history of higher weight.
Third, individuals with purging disorder do not have large, out-of-control binge-eating episodes. There may be times when they feel they have eaten too much and experience a loss of control over their eating. However, the amount of food consumed during these episodes is not more than what most people would eat under similar circumstances. For example, a person with purging disorder may go out to a restaurant with friends and share an appetizer and eat most of an entrée and then feel compelled to purge—in spite of the fact that she didn’t eat any more than her friends did.
Fourth, individuals with purging disorder have significant body image disturbances, including an undue influence of weight and shape on self-evaluation, an intense desire to lose weight, and intense fear of gaining weight or becoming fat. These individuals commonly describe high levels of dietary restriction that are periodically interrupted when they eat what most people would consider a snack or meal.
How Purging Disorder Differs from Other Eating Disorders
Purging disorder vs. AN. Purging disorder differs from AN on body weight. Individuals with AN are significantly underweight, whereas individuals with purging disorder are not. An important direction for future research is to determine the extent to which these weight differences may be associated with differences in treatment response, medical morbidity, and mortality between the two syndromes. However, at this time, very little work has examined the extent to which purging disorder should be viewed as distinct from AN with purging.
Purging disorder vs. BN. Purging disorder differs from BN on binge eating because individuals with BN have recurring, objectively large binge-eating episodes, whereas individuals with purging disorder do not. Purging disorder also differs from BN on levels of concern over eating, disinhibition around food, and reports of hunger, which are all lower in persons with purging disorder compared to those with BN.
In addition, women with purging disorder display a significantly greater cholecystokinin response to a fixed-size test meal compared to women with BN,4 and report significantly greater increases in fullness and stomachache following the meal compared to both women with BN and control subjects without eating disorders.4 These findings suggest differences in appetite regulation between purging disorder and BN, in which purging disorder may be characterized by excessive satiation and BN may be characterized by deficient satiation. ConsequentlyGiven differences found between BN and purging disorder, clinicians should take care in assessing the size of binge-eating episodes during intake evaluations of normal-weight patients who report binge eating and purging.
Purging disorder vs. BED. Purging disorder differs from BED based on the central behavioral feature of each syndrome. In addition, individuals with BED tend to be overweight or obese, whereas individuals with purging disorder tend to be within a normal weight range. However, beyond these descriptive differences, very little work has been done to examine other differences between purging disorder and BED.
Patterns of Comorbidity in Purging Disorder
Individuals with purging disorder have elevated rates of mood, anxiety, and substance-use disorders compared to individuals without eating disorders. Of these, anxiety disorders appear to co-occur with purging disorder most often. ComorbidCurrent anxiety disorders are reported in 39%5 to 43%6 of women with purging disorder. Rates of current mood disorders appear to be lower in purging disorder than in BN, in which mood disorders tend to be the predominant comorbid diagnosis. Although not statistically significant, women with purging disorder also report slightly higher rates of current substance-use disorders compared to women with BN.5,6 Given the elevated risk of mortality associated with substance use disorders in their own right 7 and when combined with eating disorders,8 clinicians should watch for patterns of alcohol and drug use in these patients.
Treating Purging Disorder
At this time, there are no evidence-based treatments for purging disorder because no controlled treatment trials have been conducted for this syndrome. Thus, clinicians should consider adopting an individual-case-approach when treating their patients with purging disorder. That is, we should conduct careful assessments of symptom levels at baseline before starting any treatment. Then symptom levels should be reassessed during different treatment phases to examine whether specific interventions are associated with reductions in specific symptom features. For example, if a clinician plans to adopt cognitive behavioral therapy using a transdiagnostic approach, then the clinician should measure and document if reductions in purging are observed with psychoeducation and behavioral interventions and should similarly assess whether changes in body image disturbance accompany cognitive interventions. Of note, among patients with higher premorbid weight, clinicians may encounter greater resistance to interventions if reductions in dietary restraint and purging behaviors lead to rapid weight gain.
Purging disorder is a clinically significant disorder of eating for which patients seek treatment. Based on personal communications with individuals with purging disorder, many are frustrated when clinicians diagnose them with BN and then initiate treatments for symptoms that they do not have. At this time, it is not clear what forms of treatment may be most beneficial. Thus, clinicians are encouraged to provide careful assessment of specific features of their patients, with particular attention to how clinical presentation may differ from that typically seen in the defined disorders of AN, BN, and BED. Although treatments that have demonstrated efficacy in the treatment of other eating disorders may be useful for treating purging disorder, it would be a disservice to patients with purging disorder to assume that this is the case. Instead, clinicians should monitor progress throughout treatment, and document those interventions that appear to be useful and those that result in little or no improvement in symptoms. Finally, clinicians are encouraged to share their experiences in treating patients with purging disorder because published case series can provide important data for the development of treatment interventions to be tested in controlled treatment trials.
About the Author
Pamela Keel, Ph.D. is currently Associate Professor of Psychology at the University of Iowa. She is the author of numerous articles and reviews, and two books, Eating Disorders (Prentice Hall, 2005) and Eating Disorders (Psychological Disorders series (Chelsea Hall Publishers). She was co-convener for the 2008 International Conference on Eating Disorders in Seattle.
References and Suggested Reading
1. Mitchell JE, Pyle RL, Hatsukami D, Eckert ED. What are atypical eating disorders? Psychosomatics. 1986; 27:21.
2. American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R), 3rd ed, revised. Washington, DC: American Psychiatric Association, 1987.
3. Keel PK: Purging disorder: Subthreshold variant or full-threshold eating disorder? Int J Eat Disord. 2007; 40:S89.
4. Keel PK, Wolfe BE, Liddle RA, DeYoung KP, Jimerson DC. Clinical features and physiological response to a test meal in purging disorder and bulimia nervosa. Arch Gen Psychiatry. 2007; 64:1058.
5. Keel PK, Haedt A, Edler C: Purging disorder: an ominous variant of bulimia nervosa? Int J Eat Disord. 2005; 38:191.
6. Keel PK, Wolfe BE, Gravener JA, Jimerson DC. Comorbidity and disorder-related distress and impairment in purging disorder. Psychol Med. ( in press).
7. Harris EC, Barraclough B. Excess mortality of mental disorder. Br J Psychiatry. 1998; 173:11.
8. Keel PK, Dorer DJ, Eddy KT, Franko D, Charatan DL, Herzog DB. Predictors of mortality in eating disorders. Arch Gen Psychiatry. 2003; 60:179.