Abstract
BACKGROUND: Body dysmorphic disorder (BDD) is particularly prevalent yet highly understudied and undertreated in adolescence. This study evaluates the efficacy of an internet-based, therapist-guided cognitive behavioral therapy (CBT) for adolescents and young adults with BDD compared to supportive online therapy as an active control condition. METHODS: In a single-blind, randomized controlled trial, N = 45 adolescents (aged 15-21 years) of all genders from German-speaking countries were assigned to 12 sessions of internet-based CBT (iCBT) or 12 weeks of supportive online therapy. The primary outcome was change in expert-rated BDD symptom severity from pre- to post-intervention (Yale-Brown Obsessive-Compulsive Scale Modified for Body Dysmorphic Disorder, BDD-YBOCS). Secondary outcomes included the remission and responder rate, changes in delusionality of appearance beliefs (BABS), self-rated BDD symptom severity (FKS), BDD cognitions (FKDK), quality of life (KINDL-R), and depressive symptoms (PHQ-9) from pre to post and to a 4-week follow-up. RESULTS: iCBT was more efficient than supportive online therapy on the BDD-YBOCS (p =.002), with a large between-group effect size at post-intervention (Hedges' g (SE) = 0.93 (0.42)), and on all secondary measures (p <.05), except for depressive symptoms (p =.068). All secondary outcome measures also showed significant improvements from pre to post iCBT, with moderate to large effect sizes, and gains were stable until the 4-week follow-up period. iCBT participants showed higher remission (61.5%) and responder rates (66.7%), compared to controls (0% and 26.7%), but only the difference in remission reached significance. CONCLUSION: The results indicate the efficacy of internet-based CBT in comparison to an active control condition, thus contributing to the limited intervention research in adolescent BDD and adding a much-needed treatment option. TRIAL REGISTRATION: The trial was pre-registered on 2020/06/08 at the German Clinical Trials Register, DRKS00022055.