MAOA and mental disorder: One clinical experiment suggested a role for ESR1 in the etiology of PPD, possibly through modulation of serotonin signaling.[44] Previous work has demonstrated that exposure to and withdrawal from normal levels of gonadal steroids results in depressive symptomatology in women previously diagnosed with PPD.[45,46] The MAOA gene, located on the short arm of the X-chromosome (Xp11.4-p11.3), has been the focus of research in the field of mental disorders in recent years.