Distinctive Microbiome Associated With Schizophrenia

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A recent study may have found a link between bacteria found in the mouth and throat and schizophrenia. Leonhard Foeger/Reuters

Scientists continue to discover ways that the viruses, bacteria and fungi that make a home in the human digestive system—also known as the human microbiome—may help further illuminate how the brain works, why it malfunctions, and especially what causes certain psychiatric illnesses.

A new study, published Tuesday in Peer J, for example, is a comprehensive analysis of bacteria in the throat of patients with schizophrenia. Researchers at the George Washington University identified differences in the bacteria found in people with schizophrenia compared with people without this psychiatric condition.

The study looked at the oropharyngeal (mouth and throat) bacteria in 16 individuals with schizophrenia and 16 without the psychiatric disorder. It found that those with schizophrenia had higher levels of lactic acid bacteria—a type of bacteria that has been associated with the control of chronic inflammation. Additionally, the researchers found differences in the microbial metabolic pathways of patients with schizophrenia. These pathways are influenced by the levels of certain bacteria, and are related to the transport system of certain compounds, like vitamin B-12 and glutamate, a neurotransmitter.

"Our results suggesting a link between microbiome diversity and schizophrenia require replication and expansion to a broader number of individuals for further validation," said Keith Crandall, director of the GWU's Computational Biology Institute and contributing author of the study, in a press statement. "But the results are quite intriguing and suggest potential applications of biomarkers for diagnosis of schizophrenia and important metabolic pathways associated with the disease."

There are some 100 trillion bacteria in the average person’s body, outnumbering even human cells. Researchers already know that the microbiome plays a huge role in human health and may help to determine whether a person develops certain chronic health problems, including psychiatric and neurological conditions, cancer, diabetes and obesity. A number of factors influence the bacteria population in the body, including food, water, pollution and lifestyle habits such as exercise and smoking. Interestingly, another study identified some microbiome differences in patients who took valproate, a drug used to manage seizures and mood disorders that’s sometimes prescribed to patients with schizophrenia. In some patients, the drug appeared to impact levels of a certain virus that invades and replicates inside bacteria, which ultimately alters the microbiome.

Though research is still preliminary, some argue that targeted therapies, such as certain probiotic supplements,  may in the future change the way conditions like schizophrenia are actually treated.