HTR1A and major depressive disorder: Eight of twelve MDD-related genes exhibited significant correlations with regional changes in MSN (all pFDR < 0.05; Fig. 3e), including five negative correlations (i.e., CNR1, HTR1A, PDE1A, SST, and TAC1) and three positive correlations (i.e., ARRA2A, CHRM2, and CUX2).