In a sample of 20 inpatients with a DSM-IV-TR/DSM 5 diagnosis of schizophrenia or schizoaffective disorder, investigators propose to conduct a prospective, 2 week observational trial to collect gastrointestinal stool samples in order to characterize the microbiota in people with schizophrenia and examine its variability over time. Participants may elect to participate for an additional two weeks, during which they will receive the prebiotic, oligofructose-enriched inulin (FOS), in order to examine its effects on the relative preponderance of butyrate-producing bacteria in the gut microbiome. Investigators will use an inpatient sample in order to standardize meals, exercise and environmental mediators. This is considered a feasibility, pilot study in order to apply for future grant funding. Investigators will recruit patients from the Treatment Research Program inpatient unit, Maryland Psychiatric Research Center, University of Maryland School of Medicine.

Inclusion Criteria:

1. DSM-IV-TR /DSM 5 diagnosis of schizophrenia or schizoaffective disorder;
2. Age 18-64 years;
3. currently hospitalized for at least 7 days
4. currently treated with an antipsychotic, with no dose changes in last 14 days
5. ability to participate in the informed consent process, as determined by a score of 10 or greater on the Evaluation to Sign Consent

Exclusion Criteria:

1. Gastrointestinal disorders, including, but not limited to Crohn's Disease, Irritable Bowel Syndrome, Celiac Disease,
2. Organic brain disorder, including cerebrovascular accident; epilepsy; traumatic brain injury, Loss of consciousness (LOC) for more than 30 minutes
3. Mental retardation
4. Antibiotic or immune therapy within the last three months
5. Prebiotic or probiotic treatment within the last three months
6. Inability to understand English
7. Inability to cooperate with study procedures
8. Pregnant women
9. Prisoner status
10. For MRI ONLY Contraindication for MRI scanning (e.g. metal in body, pacemaker).

In-participants with Schizophrenia