Effects of Intranasal Oxytocin on Satiety Signaling in People With Schizophrenia

Inclusion Criteria: * DSM-IV diagnosis of schizophrenia or schizoaffective disorder * Male or Female * Age: 18 to 54 years * Caucasian or Non-Caucasian * Body Mass Index of ≥ 27 kg/m2 * One month of stable antipsychotic treatment (same medication regimen and same dose) Exclusion Criteria: * History of organic brain disease * DSM-IV diagnosis of Mental Retardation * DSM-IV diagnosis of Alcohol or Substance Dependence within the last six months (except nicotine) * DSM-IV diagnosis of Alcohol or Substance Abuse within the last one month (except nicotine) * Are pregnant or lactating * Meet DSM-IV criteria for a past and/or current eating disorder via the SCID, or if they have a past medical history of an eating disorder, received treatment/counseling for an eating disorder and/or required hospitalization for an eating disorder. (If an otherwise undiagnosed eating disorder is detected during screening, referral to treatment will be provided.) * Are taking weight-loss medications, whether over-the-counter (i.e. Hydroxycut, Stacker products, Metabo-Plus, CortiSlim), or prescribed, including appetite suppressants (Didrex, Tenuate, Sanorex, Mazanor, Adipex-P, Meridia, and Phentermine) and fat-absorption inhibitors (Xenical). * Have cognitive impairment severe enough to preclude informed consent or valid responses on questionnaires. This is defined an as a score of less than 10 on the Evaluation to Sign Consent (ESC). * Have a medical illness, dietary restrictions, or food allergies that, in the view of the investigators, would compromise participation. * Are taking prostaglandins such as dinoprostone or misoprostol (because they interact with oxytocin).