The Appearance Anxiety Inventory (AAI) is a self-report measure assessing the typical cognitions and behaviours of body dysmorphic disorder (BDD). Despite its use in research and clinical settings, its psychometric properties have not been evaluated in young people with BDD. We examined the factor structure, reliability, validity, and sensitivity to change of the AAI in 182 youths with BDD (82.9% girls; Mage = 15.56, SD = 1.37) consecutively referred to two specialist outpatient clinics in Stockholm, Sweden (n = 97) and London, England (n = 85). An exploratory factor analysis identified three factors, namely "threat monitoring", "camouflaging", and "avoidance", explaining 48.15% of the variance. The scale showed good internal consistency (McDonalds omega = 0.83) and adequate convergent validity with the Yale-Brown Obsessive-Compulsive Scale Modified for Body Dysmorphic Disorder for Adolescents (BDD-YBOCS-A; rs = 0.42) and the Clinical Global Impression-Severity Scale (rs = 0.32). Sensitivity to change was adequate, with AAI total scores and individual factor scores significantly decreasing over time in the subgroup of participants receiving multimodal treatment for BDD (n = 79). Change of AAI scores over treatment showed a positive statistically significant moderate-to-good correlation (r = 0.55) with changes in BDD symptom severity, measured by the BDD-YBOCS-A. The study provides empirical support for the use of the AAI in young people with BDD in clinical settings
