Hence, the available data related to MAOA expression in mood disorders in other ethnicities are very limited, whereas the role of MAOA-30 bp μVNTR in common psychiatric conditions, including MDD, BD, and SHZ, in individuals of Pakistani descent has not been established yet; therefore, the current study aimed to investigate the genetic association of promoter region functional polymorphism (MAOA-30 bp μVNTR) with MDD, BD, and SHZ, and the effect of different repeat alleles on MAOA serum levels in cases compared to controls in the Pakistani population. This evidence concerns the gene MAOA and mood disorder.