Predictors of response to family-based treatment for anorexia nervosa in youth: insights from the VIBUS project.

Anorexia nervosa (AN) is a severe psychiatric disorder often emerging during adolescence, with physical, psychological, and social consequences. Family-based treatment (FBT) is the first-line intervention for young persons (YP) with AN, empowering parents to manage their child's renourishment. Despite its benefits, less than half of YPs achieve full recovery by the end of treatment. Previous predictors, such as early weight gain, cognitive rigidity, and family dynamics, have been linked to poor outcomes, but further research is needed to refine treatment strategies. This study aimed to evaluate predictors of treatment outcomes in a large cohort consisting of 653 YP undergoing FBT for AN. Three key outcomes were examined: weight gain trajectories, time to successful treatment completion, and the risk of intensified treatment (inpatient or day patient care). The study was conducted as part of the VIBUS project, a prospective, naturalistic case series. Weight gain occurred primarily in the first three months of treatment. Older age and comorbid behavioural or emotional disorders predicted less weight gain. YPs with lower baseline BMI, higher eating disorder severity, family adversities, or comorbid conditions took longer to complete treatment, with BMI at four weeks emerging as a key predictor. Lower baseline BMI and reduced maternal renourishment capacity increased the risk of intensified treatment. These findings highlight early risk factors for suboptimal FBT response, suggesting the need for targeted interventions to improve outcomes and reduce reliance on more intensive treatments. Clinical trial registration: ClinicalTrials.gov Identifier: NCT05956366, register date 2023-07-13.