DAO and schizophrenia: Given that d‐serine is an NMDAR co‐agonist, the overactivity of DAO (and resulting insufficiency of d‐serine) could contribute to the NMDAR hypofunction proposed to exist in schizophrenia (Olney et al., 1999; Kantrowitz & Javitt, 2010; Marek et al., 2010; Verrall et al., 2010; Coyle, 2012; Labrie et al., 2012).