Baseline eating disorder severity predicts response to an acceptance and commitment therapy-based group treatment

• Acceptance and Commitment Therapy may be an effective therapy for eating disorders.
• The study assessed whether more severe eating pathology moderated the effect of ACT.
• Severity of self-reported eating pathology moderated treatment effects.
• More severe pathology made greater gains in ACT than in treatment-as-usual.
• Similar patterns were found for previous hospitalizations and low weight in AN.

The present study investigated whether more severe baseline eating pathology (e.g. baseline symptomatology, previous hospitalizations, and low weight in anorexia nervosa) moderated the effect of an Acceptance and Commitment Therapy (ACT)-based group treatment. Participants were 140 women who were admitted to an inpatient facility for eating disorders. Women were categorized as anorexia nervosa spectrum or bulimia nervosa spectrum at intake and completed measures of eating pathology. All participants received comprehensive treatment, and those in the treatment-as-usual plus ACT condition received twice weekly ACT group treatment. At post-treatment (i.e., at discharge from the facility), participants completed measures again. Severity of self-reported eating symptomatology moderated treatment such that those with more severe symptoms at baseline showed greater improvements in eating disorder symptomatology in the ACT condition than in the treatment-as-usual condition. Additionally, trends showed similar patterns for those with more previous hospitalizations and those on the anorexia nervosa spectrum who had lower body weights. The magnitude of differences was modest, but indicates that an acceptance-based treatment may be a beneficial for patients with more severe eating disorder pathology.