 Increased levels of another NMDA antagonist, kynurenic acid, may aggravate the symptoms of schizophrenia, according to the "kynurenic hypothesis".NMDA receptor antagonists can mimic these problems; they sometimes induce "psychotomimetic" side effects, symptoms resembling psychosis.Such side effects caused by NMDA receptor inhibitors include hallucinations, paranoid delusions, confusion, difficulty concentrating, agitation, alterations in mood, nightmares, catatonia, ataxia, anesthesia, and learning and memory deficits.