MAOA and major depressive disorder: The 4R allele of the MAOA uVNTR (0 referred to 4R and 1 referred to 3R in the SEM) did not have a direct effect on attempted suicide in subjects with MDD, but it did have an indirect effect through the mediating factor of depressive symptoms (MAOA-depression: β = -0.12, p = 0.031; depression-suicide: β = 0.32, p < 0.001).