Predictors and moderators of treatment outcome in a randomized clinical trial for adults with symptoms of bulimia nervosa

Abstract

Objective: This study examined predictors and moderators of outcome in 2 treatments for bulimia nervosa (BN).

Method: Eighty adults with BN symptoms at 1 of 2 sites were randomized to 21 sessions of integrative cognitive-affective therapy for BN (ICAT-BN) or enhanced cognitive behavior therapy (CBT-E). Generalized linear models examined predictors and moderators of improvements in bulimic behavior and eating disorder psychopathology at end of treatment (EOT) and 4-month follow-up (FU).

Results: At EOT, individuals with higher dietary restraint had greater reductions in bulimic behavior. At FU, individuals with higher weight and shape concern had greater reductions in bulimic behavior, whereas those with greater baseline depression had less improvement in eating disorder psychopathology. Individuals higher in stimulus seeking had greater reductions in bulimic behavior and eating disorder psychopathology at follow up in ICAT-BN than in CBT-E, whereas individuals lower in stimulus seeking had greater reductions in bulimic behavior in CBT-E than in ICAT-BN. Finally, individuals with higher affective lability had greater reductions in eating disorder psychopathology in ICAT-BN than in CBT-E, whereas improvements were comparable across treatments for individuals with lower affective lability.

Conclusions: This study identified 3 nonspecific predictors of outcome (i.e., dietary restraint, weight and shape concern, and depression) and 2 moderators (i.e., affective lability and stimulus seeking). All moderator effects emerged at FU rather than at EOT, suggesting that the moderating effects of treatment were not immediately apparent. These results suggest that individuals with higher affective lability and stimulus seeking may benefit more from treatment with a greater focus on affective states and self-regulation.

Trial registration: ClinicalTrials.gov NCT00773617.

(c) 2016 APA, all rights reserved).

Figures

Figure 1

Bulimic behavior (count of objective binge episodes and purging behaviors in the past 28 days) at four-month follow-up by treatment and level of stimulus seeking (high = 1SD above the mean, low = 1SD below the mean).

Figure 2

Bulimic behavior (count of objective binge episodes and purging behaviors in the past 28 days) at four-month follow-up by treatment and level of affective lability (high = 1SD above the mean, low = 1SD below the mean).

Figure 3

Eating disorder psychopathology at four-month follow-up by treatment and level of stimulus seeking (high = 1SD above the mean, low = 1SD below the mean).

Figure 4

Eating disorder psychopathology at four-month follow-up by treatment and level of affective lability (high = 1SD above the mean, low = 1SD below the mean).