Behavioral genetic methods can explicate the nature of the relationship among AN, MDD, and suicide. Genetic factors contribute to the liability to AN, MDD, and suicide (Bulik et al., 2010; Hawton, Saunder, & O'Connor, 2012; Kendler et al., 2006) and, by using a genetically informative twin sample, we can evaluate the extent to which these phenotypes share genetic or environmental factors. A recent study by Wade et al. (Wade et al., 2015) gave a glimpse into the relation among broadly defined eating disorders (including AN, bulimia nervosa, binge eating disorder, and purging disorder), MDD, and broadly defined suicidality (ranging from transitory thoughts to suicide attempts). Their model revealed a common genetic influence on eating disorders and suicidality (but not MDD), and no appreciable influence of common environmental factors.
