DRD2 and post-traumatic stress disorder: In addition to those comprehensive review studies, PTSD is found to be associated with many genes and their genotypes (21, 24), including serotonin transporter gene (SLC6A4) (25, 26), FK506 binding protein 51 (FKBP5) (27, 28), adenylate-cyclase activating polypeptide 1 (ADCYAP1R1) (29, 30), brain-derived neurotrophic factor (BDNF) (31, 32), catechol-O-methyltransferase gene (COMT) (33, 34), 5-hydroxytryptamine receptor 3A (HTR3A) (35, 36), dopamine D2 receptor (DRD2) (37, 38), nuclear receptor subfamily 3 group C member 1 (NR3C1) (39, 40), and the oxytocin receptor gene (OXTR) (41, 42).