Conventionally, effect sizes of d > .50 are considered to be “medium” and effect sizes of d > .80 be considered to be “large” (Cohen, 1998). The meta-analysis (Malouff et al., 2005) revealed that the magnitudes of association between neuroticism and mood disorders, anxiety disorders, somatoform disorders, schizophrenia, and eating disorders were all in the large range. Furthermore, studies conducted after this meta-analysis have confirmed the robust associations between neuroticism and Axis I mental disorders (Chien, Koa, & Wub, 2007; Khan et al., 2005; Weinstock, 2006). In particular, a study of 7,588 adult twins (Khan et al., 2005) found large effect sizes for the association between neuroticism and depression, generalized anxiety disorder, and panic disorder, and medium effect sizes for phobias, alcohol and drug dependence, and antisocial personality disorder. In addition, neuroticism is robustly associated with dysthymia (Akiskal et al., 2006) and there is extensive evidence that higher neuroticism is related to the use and abuse of psychoactive substances, from nicotine and alcohol to heroin (Kornør & Nordvik, 2007; Malouff, Thorsteinsson, Rooke, & Schutte, 2007; Malouff et al., 2006; Sher & Trull, 1994).
