DRD2 and major depressive disorder: A recent study combined neuroimaging and transcriptomic gene expression analyses in MDD patients receiving ECT found that increased gray matter volume correlated with higher expression levels of MDD risk genes including CNR1, HTR1A, MAOA, PDE1A and SST, as well as ECT related genes of BDNF, DRD2, APOE, P2RX7 and TBC1D14 [43].