Body dysmorphic disorder in children and adolescents : advancing the assessment, treatment, and clinician training

<p dir="ltr"><b>Background</b>: Body Dysmorphic Disorder (BDD) is a disabling mental health condition that typically begins in adolescence and causes significant distress and functional impairment. Despite its impact, research on BDD in young people remains limited, leaving important gaps in understanding and clinical care. BDD in youth is often overlooked in clinical practice, partly due to the absence of validated, age-appropriate assessment tools. Additionally, although cognitive– behavioural therapy (CBT) is effective for adults, evidence in children and adolescents remains scarce, particularly from large, real-world studies. Consequently, awareness of BDD in clinical settings remains low, and there is a shortage of trained clinicians to provide effective care, perpetuating underdiagnosis and inadequate treatment. Scalable training initiatives, such as online education programmes, offer a promising approach to enhance assessment, treatment delivery, and service capacity. There is therefore a need for targeted research in this area, alongside further evaluation of assessment tools and treatment strategies.</p><p dir="ltr"><b>Aim</b>: The overall aim of this doctoral thesis was to advance the understanding of BDD in youth and to inform improvements in clinical care. Specifically, it comprised four interrelated studies. The first study aimed to examine the psychometric properties of the Appearance Anxiety Inventory (AAI), a selfreport measure of BDD symptoms, in a clinical youth sample. The second study aimed to evaluate the acute and long-term outcomes of multimodal treatment in BDD for youths and identify predictors of response. The third study aimed to develop and assess the feasibility and preliminary effects of a supervised online training programme in BDD for clinicians in child and adolescent mental health services (CAMHS). The fourth study explored the clinicians’ experiences of the training and its use in clinical practice. </p><p dir="ltr"><b>Methods</b>: Study 1 included 182 adolescents with BDD referred to two specialist outpatient clinics in Stockholm, Sweden, and London, England, who were assessed with the AAI. The study examined the factor structure, reliability, and validity of the AAI, and tested its sensitivity to change in a subgroup receiving treatment (n = 79). Study 2 was an open trial including 140 adolescents at the same clinics who received multimodal treatment (i.e., a combination of CBT and medication when deemed necessary). Participants were assessed at baseline, post-education, and at 3-, 6-, and 12-month follow-ups. Mixed-effects regression and linear models were used to analyse outcomes and predictors. Study 3 involved 30 CAMHS clinicians in Sweden completing a 4–7-week supervised online training programme. Feasibility was assessed using descriptive statistics on acceptability, adherence, credibility, and satisfaction. Preliminary learning effects were evaluated using a custom BDD knowledge and conceptual skills test, alongside self-reported self-efficacy and application of learned content, with assessments at baseline, post-training, and six-month follow-up; analyses were conducted using descriptive statistics and mixed-effects regression models. Study 4 used semi-structured interviews with 12 clinicians, analysed with conventional content analysis. </p><p dir="ltr"><b>Results</b>: Study 1 identified a three-factor structure of the AAI—threat monitoring, camouflaging, and avoidance—with good internal consistency (ω = 0.83) and adequate convergent validity, though divergent validity was more modest. The AAI was sensitive to treatment-related change and moderately correlated with symptom improvement. Study 2 demonstrated that a multimodal treatment approach (i.e., combining CBT and medication when indicated), delivered flexibly and tailored to individual needs (e.g., number and length of CBT sessions, home visits, booster sessions) in specialist outpatient clinics, resulted in substantial reductions in BDD symptoms from baseline to post-treatment (d = 2.08). By the end of treatment, 79% of participants met responder criteria, and 59% achieved full or partial remission. Improvements extended beyond core BDD symptoms, with large gains observed in global functioning, self-reported BDD and depressive symptoms, and impairment. These benefits were sustained over 12 months, with continued improvements in clinician-rated BDD symptoms. At the 12-month follow-up, 82.2% of participants remained responders and 68.3% were in remission, accompanied by further gains in clinician-rated global functioning and self-reported impairment. Higher baseline BDD symptom severity predicted poorer post-treatment outcomes, although no consistent predictors emerged at one-year follow-up. Study 3 demonstrated that the clinician training was feasible and well-received, with high credibility and satisfaction ratings. Clinicians improved in BDD knowledge, conceptual skills, and self-efficacy, and reported applying new skills in practice. Study 4 revealed positive clinician experiences and reported changes in clinical practice, while also highlighting areas for improvement such as practical skill training and peer support. Workplace context was also described influencing educational engagement and implementation. </p><p dir="ltr"><b>Conclusions</b>: This thesis presents complementary insights for improving the identification and treatment of BDD in young people. It establishes the psychometric validity of a key assessment tool, supporting its use in clinical practice and research; indicates that a flexible, specialist-delivered multimodal treatment may be effective; and provides evidence for the feasibility and preliminary learning effects of online clinician training. While more rigorous research is needed to confirm and extend these effects, these efforts may be viewed as important steps toward strengthening clinical tools, enhance treatment delivery, and build service capacity to better address youth BDD in routine care.</p><h3>List of scientific papers</h3><p dir="ltr">I. <b>Gumpert, M.</b>, Rautio, D., Monzani, B., Jassi, A., Krebs, G., Fernández de la Cruz, L., Mataix-Cols, D., & Jansson-Fröjmark, M. (2024). Psychometric evaluation of the appearance anxiety inventory in adolescents with body dysmorphic disorder. Cognitive Behaviour Therapy, 53(3), 254-266. <a href="https://doi.org/10.1080/16506073.2023.2299837" target="_blank">https://doi.org/10.1080/16506073.2023.2299837</a></p><p dir="ltr">II. Rautio, D., <b>Gumpert, M.</b>, Jassi, A., Krebs, G., Flygare, O., Andrén, P., Monzani, B., Peile, L., Jansson-Fröjmark, M., Lundgren, T., Hillborg, M., Silverberg- Morse, M., Clark, B., Fernández de la Cruz, L., & Mataix-Cols, D. (2022). Effectiveness of multimodal treatment for young people with body dysmorphic disorder in two specialist clinics. Behavior Therapy, 53(5), 1037- 1049. <a href="https://doi.org/10.1016/j.beth.2022.04.010" rel="noreferrer" target="_blank">https://doi.org/10.1016/j.beth.2022.04.010</a></p><p dir="ltr">III. <b>Gumpert, M.</b>, Rautio, D., Birovecz, A., Jolstedt, M., Lundgren, T., Fernández de la Cruz, L., Mataix-Cols, D., & Jansson-Fröjmark, M. (2025). Supervised online training of clinicians in the assessment and treatment of young people with body dysmorphic disorder: a feasibility study. Cognitive Behaviour Therapy, 54(6), 794-812. <a href="https://doi.org/10.1080/16506073.2025.2515526" rel="noreferrer" target="_blank">https://doi.org/10.1080/16506073.2025.2515526</a></p><p dir="ltr">IV. <b>Gumpert, M.</b>, Högberg Ragnarsson, E., Birovecz, A., Rautio, D., Lundgren, T., Fernández de la Cruz, L., Mataix-Cols, D., Jansson-Fröjmark, M., & Ingvarsson, S. Clinician experiences of an online clinical training to assess and treat body dysmorphic disorder in youth: A qualitative study. [Submitted]</p>