The objective of this study is to test a single dose of intranasal oxytocin, compared to placebo, in a within subjects, crossover design, to see if oxytocin will improve satiety signaling (behaviorally and/or by self report) compared to placebo. If this single dose pilot paradigm shows an increase in satiety, it may be tested in follow-up studies as a prevention or treatment for weight gain and overeating 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).

Adverse events were collected over a period of about 4 weeks (on each of the visit days)