DAO and schizophrenia: However, as mentioned in the above section on enzymes involved in metabolism of D-serine, several researchers have now co-administered DAAO inhibitors in conjunction with D-serine in preclinical studies, and their findings suggest that DAAO inhibitors could be useful clinically in schizophrenia for reducing the required dose of D-serine and thus also reducing potential side effects associated with the administration of high D-serine (74–77).