Schizophrenia, Bipolar Disorder and the Microbiome

You’ve probably heard about the rising importance of the microbiome — otherwise known as your gut bacteria. Researchers have started to find interesting links between the naturally occurring bacteria that live in our guts, and things we’ve traditionally attributed to the brain. Things like our mood, feelings, and even thoughts. We now know, for instance, that gut bacteria can influence brain function.

What has the research found linking the microbiome to serious mental illness such as schizophrenia and bipolar disorder?

Both bipolar disorder and schizophrenia are serious forms of mental illness that significantly impact a person’s mood and functioning. Schizophrenia is characterized by a person experiencing delusions and hallucinations, while withdrawing from life socially and increased apathy. Some people with schizophrenia also suffer from reduced cognitive abilities and impaired social functioning. Bipolar disorder is characterized by swings in mood between mania and severe depressive episodes.

Both disorders are marked by significant distress in the person’s life who experiences them and a positive response to specific psychiatric medications that seem to help keep the disorder at bay. Genetic studies conducted on these disorders suggest a genetic overlap between them. However, little of the risk of being diagnosed with either disorder have been reliably associated with a distinct set of genes.

Researchers (Dickerson et al., 2017) have recently reviewed the connection between the microbiome, immunity, and these disorders to better understand their relationship. “Previous studies have demonstrated that both schizophrenia and bipolar disorder are associated with alterations of the systemic immune system including low-grade chronic inflammation (increased plasma cytokines, soluble cytokine receptors, chemokines, acute phase reactants) and T-cell activation features.”

Although the recent focus on the microbiome is new, research dating back to the 1950s showed us the connection between the gut and these disorders. “One of the earliest specific documentations of GI inflammation associated with schizophrenia was a post-mortem study of 82 individuals with schizophrenia, where researchers found that 50% had gastritis, 88% enteritis and 92% colitis.” We know the microbiome is connected to these disorders — but we still don’t know exactly how. GI inflammation appears to be an important consideration as well.

Antimicrobial agents may also help shed light in this area, as they can be used as a measure of bacterial infection. In one recent study of 234 hospitalized patients with acute mania, the researchers found “that in patients with acute mania, but not those hospitalized for the other conditions, had a substantially increased rate of recent antimicrobial prescription when adjusting for demographic variables. Within the mania group, the prescription of antibiotics was associated with having increased mania symptom severity but not with other clinical ratings.”

Could probiotics — the things that are supposed to help even out a person’s gut bacteria — then help a person with schizophrenia or bipolar disorder? A recently completed research study suggests that the jury is still out. In that 2014 study using probiotics in people who had been diagnosed with schizophrenia, there was no significant difference in the psychiatric symptoms between the people who had taken the probiotics versus a control group that had taken placebos. Other clinical trials are ongoing to explore this relationship further.

Among the limitations in our current research knowledge is “whether changes in the microbiota associated with schizophrenia and bipolar disorder are state or trait related and how the microbiome may be involved in mood switching in bipolar disorder and in psychotic exacerbations in schizophrenia.” That is, do the disorders influence and cause the problems in the gut bacteria’s makeup, or are the disorders caused (or significantly influenced) by the gut bacteria themselves.

There’s a lot more research needing to be done in this area in order to get to the answers behind this intriguing connection. Until it’s done, we have a lot more questions than answers about how these things are connected.

Schizophrenia & the Microbiome


Special thanks to Elsevier’s ScienceDirect for access to this research article.



Dickerson, F., Severance, E., Yolken, R. (2017). The microbiome, immunity, and schizophrenia and bipolar disorder. Brain, Behavior, and Immunity, 62, 46-52.