Nine genes selected based on their relations with depression include: SLC6A4 [50], FKBP5 [51], ADCYAP1R1 [52], BDNF [53], COMT [54], HTR3A [55], DRD2 [56], NR3C1 [57], and OXTR [58]. This evidence concerns the gene DRD2 and major depressive disorder.