If you live with bipolar disorder, or love someone who does, you may have wondered whether your gut has anything to do with it. Your gut holds trillions of bacteria, collectively called your gut microbiome, and researchers have spent roughly the last decade studying how they influence the rest of your body, including your brain. Bipolar disorder has long been explained through brain chemistry and genetics. Now some scientists are asking whether the gut plays a supporting role too. This research is young. None of it shows that gut bacteria cause bipolar disorder, and none of it changes how the condition should be treated today. But a few findings are specific enough to walk through, especially if this topic matters to you personally.
How your gut and brain stay in touch
Your gut and brain communicate through several channels at once. One is the vagus nerve, a long nerve running from your brainstem down into your gut that carries signals in both directions, a route researchers are also tracing in Parkinson's disease. Gut bacteria also produce chemicals that reach your brain directly, including building blocks for serotonin, a brain chemical involved in mood regulation. About 90% of the body's serotonin is made in cells lining your gut rather than in your brain itself[1]. Researchers call this whole network the gut-brain axis, and it appears to shape mood, inflammation, and stress response, all of which come up in bipolar disorder as well as in other conditions researchers are studying, including ADHD in kids.
What the studies have found
A couple of studies stand out from the rest, one observational and one a randomized trial. Neither is large enough to settle anything on its own, but both point in the same general direction.
115 people with bipolar disorder vs. 64 without. The bipolar group had a smaller share of a bacterium called Faecalibacterium, and within that group, having more of it lined up with better self-reported mood, sleep, and anxiety scores[2]. The finding is an association, not proof that the bacterium changes symptoms.
66 people given a probiotic or placebo for 24 weeks after a hospital stay for mania. The probiotic group was rehospitalized less often over that period, 8 people versus 24, and had shorter hospital stays when they were readmitted[3]. The result came from a randomized trial, though it was small and has not yet been repeated at a larger scale.
"The data support the hypothesis that targeting the microbiome may be an effective treatment paradigm for bipolar disorder." Sophie J. Evans and colleagues, University of Michigan, Journal of Psychiatric Research, 2017.
Why cause and effect are still unclear
Mood stabilizers and antipsychotics, medications that calm overactive brain activity, can change gut bacteria on their own. So can diet, sleep, exercise, and stress, all of which tend to shift together during a mood episode. That overlap makes it hard to tell whether a gut difference helps drive symptoms, results from treatment, or just happens to move alongside something else. Sorting that out takes larger studies that track people over time, and most of the current research isn't built to do that yet, much like the early-stage work on psychosis and schizophrenia and the gut.
What this isn't
None of this research works as a diagnostic tool. A stool sample can't tell you whether you have bipolar disorder or when your next mood episode might hit. No probiotic or supplement has been proven to treat or prevent it. Coverage of this topic sometimes turns one small, promising study into a headline that claims more than the data supports, so read past the headline, or ask your psychiatrist what they make of a given study.
- Gut microbiome findings do not diagnose bipolar disorder
- No supplement or probiotic replaces a prescribed mood stabilizer or antipsychotic
- Never stop or change a psychiatric medication based on a study or an article, this one included
- Talk to your psychiatrist before adding any supplement, since some interact with medications used for bipolar disorder
- If you're having a mood episode or thoughts of self-harm, contact your care team or a crisis line right away
What to do with this
Bring this article, or one question it raised, to your next psychiatrist appointment. If you're curious about the two studies above, ask what they think of the findings and whether anything here applies to your situation. That conversation matters more than any supplement you could pick up on your own.
This content is for educational purposes only and is not a substitute for professional medical advice.
- Cleveland Clinic, "Serotonin." Read the article
- Evans et al., "The gut microbiome composition associates with bipolar disorder and illness severity," Journal of Psychiatric Research, 2017. Read the study
- Dickerson et al., "Adjunctive probiotic microorganisms to prevent rehospitalization in patients with acute mania: A randomized controlled trial," Bipolar Disorders, 2018. Read the study
