HTR1A and major depressive disorder: C(−1,019)G (rs6295) is a functional 5-HT1A promoter polymorphism that modifies 5-HT1A gene expression in a brain region-specific manner (Le Francois et al., 2008) and modify connectivity such as amygdala-ventrolateral prefrontal cortex, and corticolimbic connectivity related to MDD (Vai et al., 2017).