Is There a Link between Oropharyngeal Microbiome and Schizophrenia? A Narrative Review

Abstract

The study aimed to examine the impact of the oropharyngeal microbiome in the pathophysiology of schizophrenia and to clarify whether there might be a bidirectional link between the oral microbiota and the brain in a context of dysbiosis-related neuroinflammation. We selected nine articles including three systemic reviews with several articles from the same research team. Different themes emerged, which we grouped into 5 distinct parts concerning the oropharyngeal phageome, the oropharyngeal microbiome, the salivary microbiome and periodontal disease potentially associated with schizophrenia, and the impact of drugs on the microbiome and schizophrenia. We pointed out the presence of phageoma in patients suffering from schizophrenia and that periodontal disease reinforces the role of inflammation in the pathophysiology of schizophrenia. Moreover, saliva could be an interesting substrate to characterize the different stages of schizophrenia. However, the few studies we have on the subject are limited in scope, and some of them are the work of a single team. At this stage of knowledge, it is difficult to conclude on the existence of a bidirectional link between the brain and the oral microbiome. Future studies on the subject will clarify these questions that for the moment remain unresolved.

Oropharyngeal microbiome composition as a possible diagnostic marker for true psychosis in a forensic psychiatric setting: A narrative literature review and an opinion

“…Human oral microbiota has turned into a highly focused research interest since bacterial products, oral bacteria, and inflammatory molecules are capable of invading the human body through the digestive tract or bloodstream [7]. Huge differences were observed in the present review between the oropharyngeal microbiota of psychotic patients and controls (Table 1).…”

“…Although no study has yet directly examined the possible diagnostic role of oropharyngeal microbiome composition among forensic psychiatric patients with psychosis, but such a hypothesis does not seem very unlikely based on the available evidence [7,[14][15][16][17][18][19][20][21][22][23]. A possible explanation for our hypothesis is a state of neuroinflammation existing in psychotic patients [7].…”

“…A considerably greater abundance of Porphyromonas gingivalis was also observed in the schizophrenia patients' saliva compared to healthy controls [21], leading to a state of neuroinflammation [22,23]. However, it seems hard to comment on the presence of a bidirectional link between the oropharyngeal microbiome and the brain at this stage of knowledge [7]. Certainly, more research is needed to give a clear answer to the remaining questions in this area.…”

“…In this respect, recent scientific evidence has shown major differences in the oropharyngeal microbial composition between psychotic patients and healthy subjects [7]. Such a hypothesis seems almost likely according to the available evidence despite that no study has been conducted directly on how oropharyngeal microbiota plays a feasible diagnostic role among forensic psychiatric patients with psychosis.…”

Deleterious Effect of Air Pollution on Human Microbial Community and Bacterial Flora: A Short Review

“…Most recently, oral microbiota dysbiosis has emerged as one of the contributing factors to diseases such as schizophrenia and osteoporosis. Until now, probiotics were found to be useful for the restoration of oral dysbiosis [ 41 ]. Similarly, several molecules from saliva form a specific film to minimize dysbiosis; therefore, the process of dysbiosis may increase if the amount of saliva decreases [ 42 ].…”