DAOA and major depressive disorder: Initially, DAOA was thought to be part of the central dysregulation of the glutamatergic N-methyl-D-aspartate (NMDA) receptor function, which is thought to be related to cognitive malfunction in patients with schizophrenia, depression and other neuropsychiatric disorders by effecting the long-term potentiation (LTP) pathway [3,30,31].