Neuroticism is important in the study of human psychiatric disease because of evidence that it reflects predisposition to experiencing symptoms of anxiety and depression. High neuroticism scores are robustly associated with an increased risk for depression (Angst and Clayton, 1986; Hirschfeld et al., 1989; Kendell and DiScipio, 1968; Kendler et al., 1993; Wetzel et al., 1980), and experience of a depressive episode yields an elevation in neuroticism which persists after post-recovery (i.e., a scar effect) (Reich et al., 1987). Neuroticism is known to be a strong risk factor for the lifetime prevalence of major depressive disorder (MDD) (Alnaes and Torgersen, 1997; Hirschfeld et al., 1989; Roberts and Kendler, 1999; Rush et al., 1995).
