Do anorexia and bulimia nervosa occur on a continuum? A taxometric analysis

We investigated the question of whether anorexia and bulimia nervosa occur on a continuum versus being discrete classes using two taxometric procedures: Mean Above Minus Below a Cut (MAMBAC) and Maximum Covariance (MAXCOV) analysis. Participants were N = 959 women diagnosed as having anorexia nervosa (n = 165), bulimia nervosa (n = 562) or atypical eating disorder (n = Is) or were nonclinical controls (n = 214). Indicators for the taxometric analyses were derived from the Eating Disorder Inventory, and we also included body mass index (BMI). Results replicated earlier taxometric findings in that both purging and nonpurging types of bulimia seemed qualitatively different from normative eating behavior. The distinction between restricting and binge-eating/purging types of anorexia nervosa also seemed to be qualitative rather than quantitative. However, results most consistently supported the conclusion that anorexia nervosa, binge-eating/purging type, occurs on a continuum with bulimia nervosa (both purging and nonpurging types) and that the two types of bulimia nervosa differ in degree rather than in kind. Overall, the results suggest that anorexia nervosa, binge-eating/purging type, is more qualitatively distinct from anorexia, restricting type, than from either type of bulimia nervosa, perhaps suggesting that these disorders should be reclassified in future editions of the Diagnostic and Statistical Manual of Mental Disorders.