There is mounting evidence that the 5-HTTLPR polymorphism may be one of the specific genetic variants that influence both neuroticism and the mental disorders correlated with it. For example, persons with at least one copy of the short allele of 5-HTTLPR drink more alcohol than persons with two long alleles (Munafo, Lingford-Hughes, Johnstone, & Walton, 2005). This is potentially important because neuroticism is associated with this polymorphism and higher neuroticism scores are associated with alcohol use disorders (Khan et al., 2005; Malouff et al., 2005). There also is consistent evidence that the short allele of 5-HTTLPR is associated with increased risk for depression among persons who have experienced stressful life events (Caspi et al., 2003; Lotrich & Pollock, 2004; Uher & McGuffin, 2008). Indeed, 17 studies have replicated this finding with only 3 failures to replicate (Rutter, 2008).
