DAO and schizophrenia: For the molecular biological approaches, several genes that have sex-specific genetic associations with schizophrenia were reported such as Disrupted in Schizophrenia 1 (DISC1), reelin (RELN), D-amino acid oxidase (DAO) and synapse-associated protein 97/discs, large homolog 1 of Drosophila (DLG1) in previous studies [34–37].