A link between the tiny organisms found in the throat and schizophrenia could lead to ways of identifying the causes and potential treatments of the neuropsychiatric disorder, according to new research.

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The researchers looked for differences in the levels of bacteria, fungi and virus microbes in the oropharynx region of the throat.

The peer-reviewed study was conducted by researchers at the George Washington University in Washington, DC, and is published in the journal PeerJ.

Lead author Eduardo Castro-Nallar states that an area of the throat called the oropharynx appears to contain different levels of oral bacteria in people with schizophrenia compared with people who do not have the disorder.

“Specifically, our analyses revealed an association between microbes such as lactic acid bacteria and schizophrenics,” he says.

A growing number of studies have demonstrated that the viruses, bacteria and fungi found living on and within the human body – known as the microbiome – can influence brain development, behavior and cognition.

Previously, Medical News Today have reported on studies revealing that changes to the gut microbiome can reduce cognitive functioning, improve body fat distribution and lead to anxiety and depression.

Schizophrenia is a complex mental disorder characterized by deficits in cognitive functioning, perceptions and emotional response. Research also suggests that as well as having connections with mental health, the microbiome may affect the immune system in ways that are associated with schizophrenia.

For the study, the researchers focused on the microbiome of the oropharynx, the region of the throat located at the back of the mouth, including the back third of the tongue, soft palate, tonsils and side and back walls of the throat.

Earlier research from the team identified differences in one aspect of throat bacteria between people with schizophrenia and people without the disorder. In the new study, the researchers examined the complete microbiome, looking at the viruses, bacteria and fungi present in 16 individuals with schizophrenia and 16 control participants.

The researchers report significant differences between the microbiomes of schizophrenia patients and those of the control participants. The control participants were richer in microbe species but less even in their distribution than the participants with schizophrenia.

Fast facts about schizophrenia
  • Schizophrenia occurs in 10% of people with a first-degree relative with the disorder
  • Symptoms of the disorder typically start between the ages 16-30
  • People with schizophrenia are not usually violent.

Learn more about schizophrenia

In particular, lactic acid bacteria were relatively more common in people with schizophrenia. These included species of Lactobacilli and Bifidobacterium that have previously been linked to the modulation of inflammation and anxiety in the case of the former.

The fungal species Candida dubliniensis was also found to be more abundant in participants with schizophrenia. The researchers suggest that this fungus may be associated with either altered immune responses or changes in the local environment.

“Our results suggesting a link between microbiome diversity and schizophrenia require replication and expansion to a broader number of individuals for further validation,” reports Keith Crandall, director of the Computational Biology Institute at George Washington University.

“But the results are quite intriguing and suggest potential applications of biomarkers for diagnosis of schizophrenia and important metabolic pathways associated with the disease.”

A potential confounding factor is that while 10 of the 16 participants with schizophrenia smoked, none of the control participants did, as some studies have indicated that the microbiomes of smokers and nonsmokers can differ.

The researchers conclude that if they can confirm their findings in larger and more diverse samples, such as in the gut microbiome, they will be able to shed more light on the potential links between schizophrenia and these microbes.

Previously, Medical News Today reported on a study that suggested the gut microbiome could play an important role in the production of serotonin, an imbalance of which is believed to be associated with depression.