Body dysmorphic disorder in adolescents: presentation, correlates and sex differences

Body dysmorphic disorder (BDD) is a chronic and often severe mental disorder that typically begins during adolescence, yet there is very little research conducted in this age group. This thesis explored the presentation and correlates of BDD in a sample of 3,149 Australian high school students aged 12-18 years. Chapters 2 and 3 focused on individuals with probable cases of BDD; full-syndrome BDD (pBDD) was reported by 1.7% of participants, and subthreshold BDD (sBDD) by 3.4%. Both pBDD and sBDD were associated with higher symptoms of comorbid disorders, increased mental health service use, and poorer quality of life compared to those without BDD. Chapters 4 and 5 examined sex differences in BDD symptoms in the whole sample. Chapter 4 identified a new factor structure in a measure of BDD symptoms, and cross-sex measurement invariance testing found that the measure can be used to compare BDD symptoms between male and female adolescents. As BDD symptoms varied by sex in the whole sample, cut-off scores were calculated for males and females. Chapter 5 compared competing models of the classification of BDD with anxiety, depression, obsessive-compulsive disorder, and eating disorders. In males and females, BDD symptoms formed their own factor which was correlated with affective and eating disorder factors, though many of the model parameters differed by sex. Chapter 6 examined sex differences in the presentation of BDD in pBDD and sBDD participants. Males and females did not differ in the severity of BDD symptoms, endorsement of many body areas of concern, or rates of elevated comorbid symptoms for most disorders. Further, in males, muscle dysmorphia was not associated with greater BDD severity. This thesis represents the largest known study of BDD in adolescents, and provides unique information about BDD prevalence and presentation, sex differences, and the assessment and classification of BDD symptoms.