Family-based treatment (FBT) is an efficacious intervention for adolescents with an eating disorder. Evaluated to a lesser degree among adolescents, enhanced cognitive-behavior therapy (CBT-E) has shown promising results. This study compared the relative effectiveness of FBT and CBT-E, and as per manualized CBT-E, the sample was divided into a lower weight [<90% median body mass index (mBMI)], and higher weight cohort (⩾90%mBMI).

Participants (N = 97) aged 12–18 years, with a DSM-5 eating disorder diagnosis (largely restrictive, excluding Avoidant Restrictive Food Intake Disorder), and their parents, chose between FBT and CBT-E. Assessments were administered at baseline, end-of-treatment (EOT), and follow-up (6 and 12 months). Treatment comprised of 20 sessions over 6 months, except for the lower weight cohort where CBT-E comprised 40 sessions over 9–12 months. Primary outcomes were slope of weight gain and change in Eating Disorder Examination (EDE) Global Score at EOT.

Slope of weight gain at EOT was significantly higher for FBT than for CBT-E (lower weight, est. = 0.597, s.e. = 0.096, p < 0.001; higher weight, est. = 0.495, s.e. = 0.83, p < 0.001), but not at follow-up. There were no differences in the EDE Global Score or most secondary outcome measures at any time-point. Several baseline variables emerged as potential treatment effect moderators at EOT. Choosing between FBT and CBT-E resulted in older and less well participants opting for CBT-E.

Results underscore the efficiency of FBT to facilitate weight gain among underweight adolescents. FBT and CBT-E achieved similar outcomes in other domains assessed, making CBT-E a viable treatment for adolescents with an eating disorder.

Treatment Outcome in Eating Disorders; https://clinicaltrials.gov/; NCT03599921.