BackgroundAnorexia nervosa (AN) is a serious mental illness of growing prevalence in childhood and adolescence. Despite its severity, there are still no completely satisfactory evidence-based treatments. Follow-up studies represent the most effective attempt to enlighten treatment effectiveness, outcome predictors and process indicators.MethodsSeventy-three female participants affected with AN were assessed at intake (T0) and at 6 (T1) and 12 (T2) months of an outpatient multimodal treatment program. Nineteen participants were assessed 15 years after discharge (T3). Changes in diagnostic criteria were compared with the chi-square test. Clinical, personality and psychopathology evolution were tested with ANOVA for repeated measures, using the t-test or Wilcoxon test as post-hoc. T0 features among dropout, stable and healed participants were compared. Healed and unhealed groups at long-term follow-up were compared using Mann-Whitney U test. Treatment changes were correlated to each other and with intake features using multivariate regression.ResultsThe rate of complete remission was 64.4% at T2, and 73.7% at T3. 22% of participants maintained a full diagnosis at T2, and only 15.8% at T3. BMI significantly increased at each time-point. A significant decrease of persistence and increase in self-directedness were evidenced between T0 and T2. Interoceptive awareness, drive to thinness, impulsivity, parent-rated, and adolescent-rated general psychopathology significantly decreased after treatment. Lower reward dependence and lower cooperativeness characterized the dropout group. The healed group displayed lower adolescent-rated aggressive and externalizing symptoms, and lower parent-rated delinquent behaviors. BMI, personality and psychopathology changes were related with each other and with BMI, personality and psychopathology at intake.ConclusionA 12-months outpatient multimodal treatment encompassing psychiatric, nutritional and psychological approaches is an effective approach for the treatment of mild to moderate AN in adolescence. Treatment was associated not only with increased BMI but also with positive personality development, and changes in both eating and general psychopathology. Lower relational abilities may be an obstacle to healing. Approaches to treatment resistance should be personalized according to these finding.