An example of such a mediational model is the finding that the short polymorphic allele in the promoting region linked to the serotonin transporter gene (5HTTLPR) correlates with neuroticism (Greenberg et al., 2000; Sen et al., 2004), which in turn has been shown to be associated with a tendency to interpret life events negatively (John and Gross, 2004) and therefore with higher rates of depression. Here, SLC6A4 is linked to major depressive disorder.