SLC6A4 and major depressive disorder: In humans, a variant of the upstream regulatory region of the SERT (SLC6A4) gene, the so-called short (s) allele, in comparison with long (l) allele is associated with lower SERT activity and stressed-related vulnerability to anxiety and depression (Lesch et al., 1996; Greenberg et al., 2000; Caspi et al., 2010), and also with higher body mass index (BMI) (Sookoian et al., 2007; Fuemmeler et al., 2008) and incidence of type-2 diabetes (Iordanidou et al., 2010), which are typical for the female sex and aging (Kautzky-Willer et al., 2016; Khabazkhoob et al., 2017; Batsis and Zagaria, 2018).