Some studies have suggested that the rs1800497 polymorphism is always accompanied by an abnormal expression of the DRD2 gene in the brain tissue and is associated with several psychiatric disorders, such as anxiety, depression, schizophrenia (Zhou et al., 2022), bipolar disorder (Zhang et al., 2021), and autism spectrum disorder (Liu, 2020). This evidence concerns the gene DRD2 and major depressive disorder.