An international team of researchers have discovered an interesting link between human gut bacteria and schizophrenia, a severe long-term mental health condition, whose underlying molecular mechanism still continues to elude scientists, adding to evidence that the two may be connected.

Schizophrenia is a name that loosely encompasses a range of psychological symptoms and behaviors, including psychosis, delusions, and hallucinations, all of which occur in the brain. However, a study published in Science Advances suggests that the gut microbiome may actually lead to some aspects of schizophrenia.

“We understand schizophrenia as a brain disease,” co-author Professor Ma-Ling Wong, from the State University of New York Upstate Medical University in Syracuse, said in a press briefing as reported by Discovery Magazine. “But maybe we need to re-examine this line of thinking and consider that maybe the gut has an important role.”

The team looked at the gut bacteria of 63 people suffering from the condition (both those taking medication and those who weren't) and 69 patients from a healthy control group, by sequencing genetic material from stool samples. They found that not only did people with schizophrenia have a less diverse intestinal flora, but they had certain groups of bacteria that were so distinct to the schizophrenia sufferers they were able to identify those who had it just by their gut microbiome, as well as track the severity of the condition.

The researchers also conducted fecal transplants from the schizophrenia patients into germ-free mice. They report in the study that these mice showed behaviors similar to mice that have been engineered to have a condition similar to schizophrenia. The team concludes that these findings suggest there is a connection between specific elements of the microbiome and the condition, and starting with the gut may be a way to treat schizophrenia.

Linking the metabolism of gut microbes with mental health conditions is a controversial and poorly understood field. The focus for it has been mostly on animal models, where researchers have looked at the gut-brain connection. Only recently, similar attempts have been made into understanding just how this is important in humans.

We know the gut is not just a place for food and water to be absorbed. Several important compounds, some of which are neuroactive, are produced in the human gut. Bacteria can also play a role in producing them, helping to degrade or modify these molecules, but the extent of their influence remains largely unclear.

It's also important to point out this connection doesn’t imply causation, and it doesn’t tell us if it is the condition affecting the gut flora or vice versa. We are slowly learning more about this link and it is important to continue studying further how mental conditions such as schizophrenia, depression, and anxiety and the bacteria in our digestive tract relate to each other.  

[H/T: Discovery Magazine]