The gut-brain axis is a very intriguing field that offers a lot of promise in making progress in neurological diseases. The science is still very new, though, so much work needs to be done in establishing any connections between the microbiome and these diseases. The reason the gut is normally explored is because of the strong connection between the gut and the brain via the vagus nerve, which in initial studies has been shown to be an important pathway for afferent and efferent connections. Other body microbiomes’ connections to the brain have not yet been studied. A new study that came out last week makes a connection between the oral microbiome and schizophrenia, a disease which had previously been linked to the gut microbiome. The results were published in the journal PeerJ.
The scientists performed whole genome sequencing on the oropharyngeal microbiomes of 16 people with schizophrenia and 16 healthy people. Importantly, the scientists note that the people with schizophrenia were more likely to be smokers and to be overweight, two qualities that are already associated with alterations of the oral microbiome. The results showed that the schizophrenics had lower overall diversity of their oral microbiomes compared to controls. Specifically, lactic acid bacteria, and especially Lactobacillus gasseri, were more abundant in the mouths of those with schizophrenia, even after controlling for other variables such as age and smoking status.
While this paper does not attempt to explain why these differences occur, they are quite interesting nonetheless. If somehow the disease state can be characterized by the oral microbiome this could be important for diagnostics. The next step is to actually establish if any of the connections between the bacteria in the body (including the mouth) and the brain are partly responsible causing the disease. If this is the case then not only would it help explain the environmental causes of schizophrenia, but it would also lend itself to possible microbiome treatments for the disease, such as pro- or pre-biotics.