Three separate meta-analyses of published studies concluded that there is a small but significant difference in neuroticism scores between persons with at least one short 5-HTTLPR allele and persons with only long alleles (Schinka, 2005; Schinka, Busch, & Robichaux-Keene, 2004; Sen, Burmeister, & Ghosh, 2004, 2005). A fourth meta-analysis initially did not find a significant association between 5-HTTLPR and neuroticism (Munafo et al., 2003), but a revised and updated report of this meta-analysis confirmed the significant association between 5-HTTLPR and neuroticism (Munafo, Clark, & Flint, 2005). This conclusion is consistent with findings that variations in the serotonin transporter gene in mice are related to behaviors suggestive of emotionality that may be analogous to neuroticism (Leonardo & Hen, 2006; Murphy & Lesch, 2008). In addition, functional magnetic resonance imaging has revealed that variations in alleles of 5-HTTLPR are related to variations in the activation of the amygdala and related brain structures in response to threatening stimuli (Brown & Hariri, 2006; Hariri et al., 2002; Passamonti et al., 2008). Because anatomic and functional variations in the same brain structures have been linked
