Furthermore, the interaction of 5-HTTLPR and stressful life events has been substantiated in genomic imaging studies. For example, activation of the amygdala and hippocampus in response to faces varies dramatically according to the number of stressful life events experienced by the individual, but particularly in persons with at least one short allele of 5-HTTLPR (Canli et al., 2006). Furthermore, two studies found that neuroticism entirely mediates the association between the 5-HTTLPR gene and depression (Jacobs et al., 2006; Munafo, Clark, Roberts, & Johnstone, 2006). In addition, the results of a number of cognate studies of non-human animals are consistent with the hypothesis that variants of the serotonin transporter gene interact with stress levels to influence negative emotionality (Caspi & Moffitt, 2006). There also is growing evidence that the G72 gene, which is associated with neuroticism, is also associated with major depression and schizophrenia (Rietschel et al., in press; Shi, Badner, Gershon, & Liu, 2008), suggesting that G72 could prove to be another gene that increases risk for both high neuroticism and some of the mental disorders that are correlated with it.
