Is there an optimal length of psychological treatment for eating disorder pathology?

Treatment guidelines for eating disorders (ED) are unclear about the optimal length of psychological care. We aimed to investigate associations between treatment duration and changes in ED pathology. Data for 164 outpatients accessing psychological interventions for ED were analyzed using MANOVA. We tested associations between number of therapy sessions and pre-post treatment changes in clinical outcomes (EDE-Q global scores, binge eating, purging); adjusting for baseline measures, diagnoses, and treatment type. Secondary analyses included rapid response variables in the above outcomes by treatment session eight. Partial correlations between treatment duration and BMI changes (adjusting for intake BMI) were examined for anorexia nervosa cases. Treatment duration was not significantly associated with changes in ED outcomes after adjusting for rapid response. BMI change (weight regain) was not correlated with treatment duration in anorexia nervosa cases. Rapid response was associated with better EDE-Q outcomes, but not with changes in binge eating or purging behaviors. ED outcomes are unrelated to treatment duration; rapid response is a useful prognostic indicator for treatment planning.