The purpose of this study is to understand the biologic basis of schizophrenia and to determine which symptoms are related to the illness itself and which are related to medications used to treat the illness.

Schizophrenia and related psychoses are chronic brain disorders whose prognosis is often poor and whose pathophysiology remains obscure. Brain imaging technologies such s positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and magnetic resonance imaging (MRI) offer opportunities to study the pathophysiology of psychotic disorders by evaluating brain function. However, the use of anti-psychotic drugs may interfere with the results of such studies. In this study, psychotropic medication will be discontinued in patients for a short period of time to distinguish the effects of the illness on the brain without the interference of the medication's effects on the brain. Given that there is a risk that the patient's symptoms will increase, they are asked to stay on an inpatient unit where the NIMH clinical staff is available to help them 24 hours a day.

This study will be conducted in three phases. In Phase 1, participants will be admitted to the Clinical Center while continuing to take their medication and will undergo diagnostic interviews, physical and laboratory assessments, physiological monitoring, and neuropsychological testing. Behavioral ratings will also be performed and blood and urine samples will be collected. During Phase 2, participants will continue taking medications in a blinded fashion for 8 to 12 weeks. The active medications will be replaced with a placebo (an inactive pill) part of that time. PET, fMRI, and MRI scans will be used to monitor how the continuation or lack of medication affects the brain. Psychological tests will also be given to measure changes in cognition. In Phase 3, participants will have the opportunity for clinical stabilization....