Predictors and Moderators of Response to Cognitive Behavioral Therapy and Medication for the Treatment of Binge Eating Disorder

Binge-eating disorder (BED), a research category in the DSM-IV (American Psychiatric Association, 1994), is characterized by recurrent binge-eating accompanied by feelings of loss of control and marked distress in the absence of inappropriate weight compensatory behaviors. BED is prevalent (Hudson, Hiripi, Pope, & Kessler, 2007) and strongly associated with obesity, elevated psychiatric and medical co-morbidity, and psychosocial impairment (Grilo, White, & Masheb, 2009; Hudson et al., 2007). BED differs from obesity and other eating disorders on numerous clinical markers (Allison, Grilo, Masheb, & Stunkard, 2005; Grilo et al., 2008; Grilo, Masheb, & White, 2010). Although some effective medication (Reas & Grilo, 2008) and psychological (Wilson, Grilo, & Vitousek, 2007) treatments have been identified for BED, even in studies with the best outcomes, a substantial proportion of patients do not achieve abstinence from binge-eating, and most clinical trials have reported little to no weight loss (Wilfley et al., 2002; Wilson, Wilfley, Agras, & Bryson, 2010). Thus, it is important to find ways to predict BED patients’ response to treatments as this may lead to more effective decision-making about treatment prescriptions (Kraemer, Wilson, Fairburn, & Agras, 2002). Relatively few data have been published on predictors of outcome for BED and critical reviews have highlighted the significant methodological shortcomings of most of this literature (Berkman, Lohr, & Bulik, 2007). Early studies identified several factors that may be associated with poor outcome. In some studies, severity of binge-eating (Agras et al., 1995; Agras, Telch, Arnow, Eldredge, & Marnell, 1997; Loeb, Wilson, Gilbert, & Labouvie, 2000; Peterson et al., 2000), earlier onset of BED (Agras et al., 1995), and younger age at time of presentation for treatment (Agras et al., 1997) predicted worse binge-eating outcomes, whereas psychiatric co-morbidity was generally unrelated to treatment outcomes (Wilfley et al., 2000). Recent studies, which performed more sophisticated and systematic analyses, have identified some additional potential patient predictors of treatment outcome for BED although they have generally failed to replicate many of the potential predictors identified in the first-generation studies. Hilbert and colleagues (2007) reported that greater interpersonal problems and greater shape/weight concerns predicted poorer treatment outcomes. Masheb and Grilo (2008a) reported that binge-eating frequency, eating-disorder psychopathology, and depressive levels significantly predicted their respective post-treatment levels and that personality disorders predicted higher levels of eating-disorder psychopathology and depressive levels at post-treatment. Wilson et al (2010) reported that education, depression levels, and self-esteem predicted binge-eating remission. Thus, relatively little is known about predictors of treatment outcome for BED and overall the best conclusion is that reliable predictors have yet to be identified. Even less is known about treatment moderators for BED. We are aware of six published reports of analyses of moderators (Hilbert et al., 2007; Masheb & Grilo, 2008a, Masheb & Grilo, 2008b; Robinson & Safer, 2011; Sysko, Hildebrandt, Wilson, Wilfley, & Agras, 2010; Wilson et al., 2010). Hilbert and colleagues (2007) explored numerous clinical variables but failed to find any significant moderators for CBT and interpersonal psychotherapy (IPT) delivered via intensive group formats. Similarly, Masheb and Grilo (2008a) tested numerous variables (age, psychiatric and personality-disorder co-morbidity, binge-eating, eating-disorder psychopathology, self-esteem, and depressive levels) and failed to find any significant moderator effects in a controlled trial comparing CBT and behavioral weight loss (BWL) treatments delivered via guided-self-help (i.e., CBTgsh and BWLgsh). Masheb and Grilo (2008b), in a further re-analysis of moderation effects found that two different sub-typing methods – grouping by negative-affect (Grilo, Masheb, & Wilson, 2001a; Stice & Agras, 1999; Stice & Fairburn, 2003) or by overvaluation of shape/weight (Grilo et al., 2008; Hrabosky, Masheb, White, & Grilo, 2007) – predicted worse outcomes but did not significantly moderate BED treatment outcomes. Robinson and Safer (2011) tested a broad range of demographic, psychiatric, and clinical variables and reported that the only factors that moderated better response to dialectical behavior therapy versus an active comparison group therapy were the presence of personality-disorder pathology and earlier onset of overweight and dieting. Wilson and colleagues (2010) tested numerous clinical variables including negative-affect sub-typing and reported that two variables - self-esteem and global eating-disorder psychopathology - significantly moderated treatment outcomes; patients with lower self-esteem and higher eating-disorder psychopathology benefiting more from IPT than from BWL or CBTgsh. Lastly, Sysko and colleagues (2010), in a further analysis of moderation effects in the Wilson et al (2010) trial, found that heterogeneity significantly moderated outcomes. Specifically, latent-class-analysis identified two classes of patients characterized by greater severity of binge-eating, shape/weight concerns, and depression levels, that were significantly more likely to remit from binge-eating if receiving IPT or CBTgsh. In the present study, we examined predictors and moderators of response to individual CBT and antidepressant medication for BED. This study is important for several reasons. CBT is considered the best-established treatment for BED (NICE, 2004; Wilson et al., 2007). Findings from Masheb and Grilo (2008) and Wilson et al (2010) pertain to CBTgsh (not traditional CBT) and are mixed. Antidepressant medications are considered an acceptable alternative treatment for BED (NICE, 2004). Although some studies have questioned the clinical-effects of antidepressants for BED (Ricca et al., 2001; see: Reas & Grilo, 2008), these medications are frequently and widely prescribed. If moderators of treatment response to CBT versus antidepressant medication could be identified, this would inform rationale treatment prescription.