 A kynurenic acid hypothesis of schizophrenia was proposed in 2007, based on its action on midbrain dopamine activity and NMDArs, thus linking dopamine hypothesis of schizophrenia with the glutamate hypothesis of the disease.High levels of kynurenic acid have been identified in human urine in certain metabolic disorders, such as marked pyridoxine deficiency and deficiency/absence of kynureninase.When researchers decreased the levels of kynurenic acid in the brains of mice, their cognition was shown to improve markedly.