Several mental disorders are characterized by alterations of methylation of the MAOA gene including depression, post-traumatic stress disorder, substance abuse disorders, antisocial personality disorder, conduct disorder, borderline personality disorder, and schizophrenia (Ziegler and Domschke 2018), and by different functional variable number tandem repeat (uVNTR) variants of MAOA in males and females (reviewed in Veroude et al. 2016). Here, MAOA is linked to major depressive disorder.