Affect regulation and purging: An ecological momentary assessment study in purging disorder.

Purging disorder (PD) is characterized by recurrent purging (i.e., self-induced vomiting, laxative abuse, diuretic abuse) following consumption of normal or small amounts of food and body image disturbance among women of minimally normal weight (Keel, Haedt, & Edler, 2005). Similar to Anorexia Nervosa (AN) and Bulimia Nervosa (BN), PD involves extreme efforts to control weight coupled with the undue influence of weight or shape on self-evaluation. However, in contrast to AN, purging occurs among individuals who are not underweight, and, in contrast to BN, purging occurs in the absence of objectively large binge episodes. Previous research supports the clinical significance (e.g., Keel et al., 2005; Keel, Wolfe, Gravener, & Jimerson, 2008; Mond et al., 2006; Wade, Bergin, Tiggemann, Bulik, & Fairburn, 2006) and distinctiveness of PD (e.g., Binford & le Grange, 2005; Keel et al., 2005; Keel, Mayer, & Harnden-Fischer, 2001; Keel, Wolfe, Liddle, De Young, & Jimerson, 2007; Pinheiro, Bulik, Sullivan, & Machado, 2008; Sullivan, Bulik, & Kendler, 1998; Wade, 2007; Wade et al., 2006), and suggests that the lifetime prevalence of PD is comparable to that of AN and BN (Favaro, Ferrara, & Santonastaso, 2003; Wade et al., 2006). Reflecting this growing body of literature, the DSM-5 has included PD as a named syndrome among Other Specified Feeding or Eating Disorders (American Psychiatric Association, 2013). The primary rationale for not including PD among formal diagnoses was the absence of data regarding treatment or course of PD to ensure predictive validity and clinical utility of the diagnosis (Brown, Keel, & Striegel, 2012). However, prior to the development of efficacious treatments, more research is needed to understand factors that contribute to and maintain purging behavior in PD. This study sought to test an affect regulation model of purging in PD. Very little is known about factors which serve to trigger purging in PD. The vast majority of work on purging has been conducted in the context of BN where predominant theoretical models focus on binge eating as the primary trigger for purging behavior. According to cognitive-behavioral theory proposed by Fairburn, compensatory purging develops as a way to minimize weight gain associated with large binge-eating episodes (Fairburn, 2008). As such, this explanation does not explain purging in PD or even purging episodes in AN or BN when they are not preceded by binge eating. Another line of work in BN has focused on changes in affect as an antecedent that triggers behavior and a consequence that maintains behavior to understand both binge eating and purging (Alpers & Tuschen-Caffier, 2001; Corstorphine, Waller, Ohanian, & Baker, 2006; Davis, Freeman, & Solyom, 1985; Elmore & de Castro, 1990; Kaye, Gwirtsman, George, Weiss, & Jimerson, 1986; Powell & Thelen, 1996; Rebert, Stanton, & Schwarz, 1991; Schlundt, Johnson, & Jarrell, 1986; Smyth et al., 2007). Based on evidence that purging in BN is associated with reductions in negative affect (Haedt-Matt & Keel, 2011), changes in affect represent a prime candidate for understanding purging behavior in PD. Negative affect is a risk factor for general eating pathology (Stice, 2002), and one of the most commonly cited explanations for disordered eating emphasizes the role of regulating emotional distress or negative affect. Previous research suggests that emotional factors are relevant to purging in the absence of binge eating. Cross-sectional studies (Keel et al., 2005; Keel et al., 2008; Wade et al., 2006) support elevated negative affect in PD relative to non-eating disordered controls, and laboratory studies support that food intake triggers significant increases in negative affect in women with PD compared to controls despite no differences in the amount of food consumed (Keel et al., under review; Keel et al., 2007). However, cross-sectional designs cannot establish temporal sequences of changes in affect and changes in purging necessary to establish affect as an antecedent or consequence of purging behavior, and laboratory studies have limited ecological validity. Ecological momentary assessment (EMA; Stone & Shiffman, 1994) involves repeated assessments as participants go about their daily lives and has been increasingly used to assess dynamic changes in affect related to disordered eating (Berg et al., 2013; Engel et al., 2013; Haedt-Matt & Keel, 2011). Recent findings from EMA studies of AN and BN provide important clues regarding affective influences on purging that may extend to PD.