Altered levels of MAO-A and MAO-B isoenzymes are associated with the degeneration of neurotransmitter biogenic amines such as serotonin, noradrenaline, and dopamine being suggested that they are in relation with multiple conditions such as schizophrenia, depression, antisocial aggressive behaviors, cancer, and neuropsychiatric disorders (NDs) namely PD and AD [30]. Here, MAOA is linked to major depressive disorder.