Our sample included 3,495 anorexia nervosa cases and 10,982 controls. Case definition required a diagnosis of lifetime anorexia nervosa (restricting or binge–purge subtype) or lifetime eating disorders ‘not otherwise specified’ anorexia nervosa-subtype (i.e., exhibiting the core features of anorexia nervosa). A lifetime history of bulimia nervosa was allowed given the frequency of diagnostic crossover (9). Amenorrhea was not required as it does not increase diagnostic specificity (10) [it has been removed as a diagnostic criterion in the DSM-5 (11)]. Extensive information on diagnostic and consensus procedures for the samples included in the Children’s Hospital of Philadelphia/Price Foundation Collaborative Group (CHOP/PFCG) cohort are available in (12). The cases included from the Genetic Consortium for Anorexia Nervosa/Wellcome Trust Case Control Consortium-3 (GCAN/WTCCC3) GWAS came from 12 previously collected clinical or population cohorts. Given that these were archived samples, the calculation of reliability statistics on diagnoses was not possible. Mitigating that concern, however, is that anorexia nervosa is a highly homogeneous phenotype with typical kappa values ranging from .81-.97 (13). Moreover, the approach taken here is consistent with successful GWAS meta-analysis efforts across psychiatric diagnoses, in which larger samples have overcome the challenges posed by imperfect diagnoses and small individual variant effect sizes.
