In addition, these cytokines may interfere with 5‐hydroxytryptamine (5‐HT) synthesis and glutamatergic transmission through reducing the action of indoleamine 2,3‐dioxygenase with consequent kynurenic acid accumulation; the endogenous glutamate N‐methyl‐D‐aspartate receptor antagonist that is deeply implicated in schizophrenia pathophysiology.50, 51. This evidence concerns the gene IDO2 and schizophrenia.