FIGURE 42.2 The heritability of various psychological disorders Researchers Joseph Bienvenu, Dimitry Davydow, and Kenneth Kendler (2011) aggregated data from studies of identical and fraternal twins to estimate the heritability of bipolar disorder, schizophrenia, anorexia nervosa, major depressive disorder, and generalized anxiety disorder. (Heritability was calculated by a formula that compares the extent of similarity among identical versus fraternal twins.)