People with schizophrenia are more likely to suffer from caeliac disease than the rest of the population. Scientists don't know why but a team of researchers from John Hopkins University in Baltimore looked into the prevalence of antibodies associated with gliadin, transglutinamase and endomysium - which are associated with caeliac disease - in a study of 2,301 people 1,401 of whom had schizophrenia. The researchers found that 23.1% of the schizophrenia patients had moderate-high levels of gliadin antibodies compard to 3.1% of the unaffected people. 5.4% of the schizophrenia patients had high levels of transglutaminase antibodies compared to 0.8% of the unaffected people.
Cascella, Nicola G. ... [et al] - Prevalence of Celiac Disease and Gluten Sensitivity in the United States Clinical Antipsychotic Trials of Intervention Effectiveness Study Population Schizophrenia Bulletin 37 (1), 94–100, 2011