People with schizophrenia and bipolar disorder have heightened sensitivities to certain foods, such as wheat glutens, that may leak from the gastrointestinal (GI) tract during digestion, enter the bloodstream circulation and potentially invade the central nervous system. Additionally, a leaky GI tract may also allow gut-dwelling bacteria to cross into the bloodstream and generate an immune reaction leading to inflammation. Heightened levels of inflammation in blood circulation and the nervous system have been linked to psychiatric diseases such as schizophrenia and bipolar disorder.

With her Brain & Behavior Research Foundation NARSAD Young Investigator Grant, Emily G. Severance, Ph.D. and team at Johns Hopkins University set out to test if a breached gastrointestinal barrier contributes to symptoms of psychiatric disorders. In a study published June 6, 2013 in Schizophrenia Research, the researchers measured blood markers of an endotoxin associated with bacteria found in the GI tract in patients with schizophrenia and bipolar disorder and correlated these to the levels of inflammation and immune system activation. The results can help elucidate mechanisms by which immune activation can contribute to the symptoms of schizophrenia and bipolar disorder.

At this point you might wonder what causes our GI tract to become leaky in the first place. A parasitic organism called Toxoplasma gondii can infect people when they consume raw meat or water, fruits and vegetables contaminated by feces of infected animals. Dr. Severance and her colleagues have a theory that once inside the host’s GI tract, this parasite may result in elevated antibodies against a protein called gluten, commonly found in foods containing wheat, barley and rye, which in turn can make our GI track permeable to bacteria, thus allowing them to leak into circulation. Whereas the origin of inflammation in psychiatric disorders is not well understood, a compromised GI barrier in schizophrenia could be that source of inflammation.

In this study, researchers observed that markers associated with gut-dwelling bacteria were elevated in the blood of patients with schizophrenia and bipolar disorder compared to healthy individuals. What’s more, the complex patterns of the markers surveyed suggest an activated and imbalanced immune state in these patients. The study also uncovered an interesting association of gluten antibodies in individuals who had not received any antipsychotic treatment, thus supporting the view that inflammation linked to schizophrenia is not necessarily a side-effect of the pharmacological treatment. This new study has important implications for the treatment of psychiatric disorders and supports a more focused examination of strategies that target inflammation and/or the microbiome in the gut.