MAOA and psychiatric disorder: The present study demonstrated the role of promoter region functional polymorphism (30 bp MAOA μVNTR in the etiology of multiple psychiatric disorders), and to the best of our knowledge, this current study on MAOA serum levels is the first to investigate and reveal the influence of 30 bp μVNTR in MAOA promoter on serum levels of MAOA in multiple psychiatric disorders in the Pakistani cohort.