Depression is well-known to be a polygenic and multifactorial condition, and although it shows a moderate degree of inheritance and genetic factors account for a moderate portion of its variability, the contribution of each individual gene seems to be small and influenced by other genetic and environmental factors [1,2]. One of the most investigated genetic polymorphisms regarding gene-by-environment interaction (GxE) and depression is 5-HTTLPR, a functional polymorphism in the upstream regulatory region of the serotonin transporter gene (5-HTT, SLC6A4).
