BackgroundThis study aimed to evaluate multifamily therapy (MFT) for adolescents with eating disorders (EDs) in a clinical setting, by presenting the outcome of families participating in this treatment at a specialist ED service. MFT was an adjunct to treatment at local mental health services. In particular, the study aimed to present the change in eating disorder symptoms and psychological distress from before to after treatment and at a 6 months follow-up.MethodsParticipants were 207 adolescents receiving outpatient MFT (10 or 5 months) at Oslo University Hospital in Norway between 2009 and 2022. Adolescents had heterogeneous ED presentations, with a preponderance of anorexia nervosa (AN) and atypical AN. All participants completed pre- and post-treatment questionnaires [The eating disorder examination questionnaire (EDE-Q) and the strengths and difficulties questionnaire (SDQ)]. 142 adolescents additionally completed the same questionnaires at 6 months follow-up. Weight and height were measured at all time points.ResultsLinear mixed model analyses showed that from start of treatment to follow-up, there was a significant increase in BMI percentile (p< 0.001) and a significant decrease in EDE-Q global score (p< 0.001) and SDQ total score (p< 0.001).ConclusionsThe study shows that adolescents with an eating disorder who received adjunct outpatient MFT in a real world clinical setting, experienced reductions in ED symptoms comparable to that found in a randomized controlled trial.Trial registration: The data used in this study was collected as part of routine clinical procedures for quality assurance and trial registration is therefore not required.