The Genetic Epidemiology of Purging Disorder, Anorexia Nervosa, and Obsessive Compulsive Personality Disorder

Although a variety of factors influence the development of eating disorders, genetic factors contribute notably to their etiology. Understanding genetic factors associated with eating disorders is important, as they can influence how these disorders are recognized, researched, and treated. This dissertation included two studies addressing important questions within the fields of eating disorders and genetics; specifically, Study 1 addressed the prevalence and heritability of purging and purging disorder in a population-based sample of female twins from the United States; and Study 2 investigated the nature of the co-morbidity between anorexia nervosa and obsessive compulsive personality disorder in a population-based sample of female twins from Norway. Twin methodology was applied for both studies. Univariate analyses, a bivariate Cholesky decomposition, and an item-factor modeling approach were used. Results from Study 1 revealed estimates of 3.0%, 3.4%, 3.7%, and 11.5% for self-induced vomiting, laxative and diuretic abuse, and excessive exercise, respectively. Laxative abuse was more strongly influenced by common environmental effects, while liability to excessive exercise was more strongly influenced by common genetic factors. Due to insufficient data, an item-factor model of purging disorder did not yield conclusive results. In Study 2, the phenotypic correlation between anorexia nervosa and obsessive compulsive personality disorder was 0.08. A bivariate Cholesky decomposition revealed that an AE-AEre model best fit the data, indicating that additive genetic effects moderately contribute to both anorexia nervosa and obsessive compulsive personality disorder individually but that these genetic influences are not shared between the two disorders. In addition, this model suggests that the slight overlap in liability between the two disorders is entirely accounted for by unique environmental effects and error. These results provide preliminary findings on important topics within the field of eating disorders and genetics research. Further study of the heritability of purging and purging disorder, as well as the nature of the co-morbidity between anorexia nervosa and obsessive compulsive personality disorder, is needed in large population-based samples. Better understanding the etiology of disordered eating and frequently co-occurring diagnoses, both at the diagnosis and symptom level, might have the potential to inform classification and treatment