The Effects of Kynurenine Aminotransferase Inhibition in People With Schizophrenia

Inclusion Criteria: * Males and females * Age: 18 to 55 years * DSM-5 Criteria for schizophrenia, schizoaffective disorder or schizophreniform disorder (documented by SCID) * Prescription of antipsychotic medication for at least 60 days and constant dose for 30 days prior to study entry (either first or second generation antipsychotics permitted) * Female participants must agree to use a medically accepted means of contraception Exclusion Criteria: * DSM-5 alcohol or substance misuse disorder in the last 3 months (documented by SCID) * History of an organic brain disorder; mental retardation; or a medical condition, whose pathology or treatment could alter cognition * Active disorders that have been reported to affect tryptophan metabolism or interfere with absorption will be excluded (Acute Intermittent Porphyria, Celiac Disease, Crohn's Disease, Irritable Bowel Syndrome; Brune and Pflughaupt 1975; Torres et al 2007). * Excessive self-reported daily caffeine intake, defined as intake exceeding 1000mg or the equivalent of 8 cups of coffee * Pregnancy or lactation * No metal in body that will interfere with MR imaging * Monoamine oxidase inhibitors, migraine headache medications (triptans) and dextromethorphan * Forensic or legal issues