There is growing evidence that neuroticism and mental disorders are correlated partly because they are partly influenced by the same genes (Hettema, Neale, Myers, Prescott, & Kendler, 2006; Silberg, Rutter, Neale, & Eaves, 2001; Stein & Stein, 2008). Indeed, twin studies indicate that one-third to two-thirds of the genetic variance in broad range of mental disorders is shared with neuroticism (Carey & DiLalla, 1994; Fanous, Gardner, Prescott, Cancro, & Kendler, 2002; Hettema, Neale et al., 2006). It is not surprising, then, that the genetic influences on neuroticism also increase risk for comorbidity among the many forms of mental disorders correlated with neuroticism (Khan et al., 2005).
