Examining the utility of narrowing anorexia nervosa subtypes for adults
Introduction
Symptom heterogeneity within psychiatric diagnoses can complicate treatment if intervention approaches are effective for only certain patterns of symptoms. For this reason, delineating subgroupings within a diagnosis can facilitate a clearer understanding of co-occurring symptoms, longitudinal course, and prognosis as well as inform treatment approaches. Anorexia nervosa (AN), an eating disorder associated with significant medical and mortality risk [1], [2], [3], is often unresponsive to treatment and characterized by high rates of relapse [4]. Therefore, identifying meaningful subtypes is a potentially useful strategy to improve treatment efficacy.
Consistent with the previous version, the DSM-5 [5] designates two subtypes of AN: 1) a binge-eating and purging subtype (AN-BP), characterized by binge eating, purging (e.g., self-induced vomiting, misuse of laxatives or diuretics), or a combination of binge eating and purging symptoms in the past three months, and 2) a restricting subtype (AN-R), characterized by an absence of regular binge eating and/or purging in the three months prior to diagnosis. The process of revising the DSM-IV [6] criteria for DSM-5 resulted in a re-examination of the validity of the AN-R/AN-BP subtyping scheme as well as consideration of alternative subgrouping or staging strategies [7], [8], [9]. The AN-R and AN-BP subtypes were retained in DSM-5 given higher levels of suicidality [10], [11], impulsivity and substance use [11], [12], [13], [14], and co-occurring psychiatric symptoms [15], [16], [17] reported in AN-BP compared to AN-R samples. However, these findings have not consistently been replicated and contrary findings have been observed in several studies [18], [19], [20]. Similarly, although several prospective studies have observed that AN-BP is associated with poorer outcome than AN-R [4], [21], [22], [23], other studies have not observed this difference [24]. Empirical classification studies have also been inconsistent in their support of the validity of the AN-R/AN-BP subtypes. Taxometric studies have yielded inconsistent findings about whether AN-R and AN-BP (and bulimic behavior more generally) are distinct entities or exist on a continuum [25], [26], with some evidence from taxometric and latent structure analyses suggesting that AN-BP is more similar to bulimia nervosa than to AN-R [27], [28], [29]. In addition, considerable data suggest that subtypes remain inconsistent over time, with individuals with AN-R often crossing over into the AN-BP classification [7], [18], [30].
Although these inconsistent findings potentially challenge the validity of the DSM-5 subtyping schema, alternatively, they may be the result of heterogeneity within the AN subtypes. One potential strategy to increase the clinical utility of AN subtypes is to narrow the AN-BP subtype by further delineating this category into three subcategories: binge eating without purging (i.e., binge eating only), purging without binge eating (i.e., purging only), and both binge eating and purging (i.e., combined binge eating and purging). Although some previous cross-sectional studies of this type of delineation have suggested that AN samples of individuals who purge but do not binge eat resemble AN-BP samples in terms of eating disorder psychopathology, clinical features, and comorbidity [16], other investigations have found that purging may be associated with higher levels of psychopathology than binge eating [31]. Subclassifying AN into four categories (i.e., restricting, binge eating only, purging only, and binge eating combined with purging) may potentially reduce the heterogeneity within the current AN-BP subtype and strengthen the validity and clinical utility of these diagnostic subcategories. Alternatively, further delineation may not create meaningful subgroups and could reduce the clinical utility of the current subtypes specified in DSM-5.
The purpose of the current investigation was to examine the utility of narrowing subtypes of AN to “pure” groups based on binge eating, purging, binge eating combined with purging, and restricting (i.e., the absence of binge eating and/or purging) by comparing these groups on measures of associated eating disorder symptoms, weight history, treatment history, body image, physical symptoms, and substance use. Clinically relevant differences among these four categories may indicate the usefulness of further subclassification based on patterns of binge eating and purging symptoms within the AN-BP group.
Section snippets
Participants
Study participants included 347 individuals (94.8% female; 88.2% Caucasian; mean age = 27.82 years, SD = 10.7) recruited from clinical and research settings in five states in the USA (Florida, Illinois, Minnesota, Ohio, and North Dakota) between 1977 and 2001. Study participants represent a subgroup of a larger clinical sample of eating disorder patients (N = 2966; [32]) based on meeting current DSM-IV criteria for AN as assessed by the Eating Disorders Questionnaire (EDQ; [33], [34]).
Instrument and classification
The EDQ [33],
Subtypes frequencies
Self-reported current symptoms on the EDQ yielded the following subgroups: 118 (34.0%) restricting (AN-R; no binge eating or purging); 133 (38.3%) binge eating and purging (AN-B & P; current binge eating and purging); 43 (12.4%) binge eating (AN-B; current binge eating, no purging); and 53 (15.3%) purging (AN-P; current purging, no binge eating).
Demographics, Eating Disorder Symptoms, and Substance Use
No group differences were observed on demographic variables including age (p = 0.74), race (p = 0.81), marital status (p = 0.94), or educational background (p
Discussion
This study examined the utility of narrowing AN subtypes to restricting only, binge eating only, purging only, and binge eating accompanied by purging. Although some notable differences were found in this investigation including amenorrhea history, current BMI, fasting, diet pill use, and substance use, most of these differences were observed between the AN-R and the AN-B & P and AN-P groups; few differences were found among the AN-B, AN-P, and AN-B & P groups. The fact that most of the
Conclusions
In summary, these findings do not support the validity or utility of narrowing AN subtypes based on subclassifications of different types of bulimic symptoms but do provide empirical support for the subtype classification specified in the DSM-5. Future investigations should continue to explore alternative conceptualizations for subgrouping AN [44] including dimensional models and personality, cognitive, and neurobiological variables that can potentially guide the development of effective
Conflicts
None
Acknowledgment
This project was supported by the Minnesota Obesity Center (P30DK60456), NIDDK (U01DK67429 and P30DK050456), NIMH (K02MH65919 and T32MH082761) and the Neuropsychiatric Research Institute.
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