Emerging research links the gut microbiome to mood stability. Here’s what you need to know about the benefits, limitations, and safety of probiotics.
Key Takeaways
- The gut-brain axis links digestion and mood, and gut bacterial imbalances may contribute to inflammation and mood instability in bipolar disorder.
- Early studies suggest that probiotics (beneficial bacteria) and prebiotics (the foods that feed them) may help with bipolar symptoms, but research is still emerging.
- Because supplements aren’t tightly regulated, check with your psychiatrist or doctor before adding a probiotic to be sure it’s safe for you.
- Probiotics can be a helpful add-on, but they don’t replace prescribed medication or therapy, which remain the core of treatment.
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You might not think much about the trillions of microbes living in your gut, but research shows they can play a powerful role in your mental health, including in bipolar disorder. When this delicate balance of bacteria gets thrown off, it can stir up inflammation in the body and interfere with how your brain regulates mood.
For some people, this “gut-brain connection” may mean that digestive health issues can worsen bipolar symptoms or even make them harder to manage. That’s why researchers are looking at probiotics — supplements containing beneficial bacteria — to see if they can help restore balance and support mood stability. The good news? Early studies suggest that taking care of your gut, through probiotics, diet, or lifestyle changes, might offer extra support alongside your treatment plan.
It’s not a cure, and it’s definitely not a substitute for medication or therapy, but nurturing your gut health could become another tool in your wellness toolbox.
But before you spend money on a probiotic, it helps to understand the science behind gut health and how it connects to bipolar disorder. Here are six things to know before deciding whether probiotics are worth adding to your plan.
Probiotics May Work Through the Gut-Brain Connection
You may not know it’s happening, but your gut and brain are in constant communication. This is what’s known as the gut-brain axis. According to a review of existing research, there are 200 to 600 million neurons connecting the digestive tract to the brain. This is a two-way connection:
- Your brain sends signals to your digestive tract via nerve cells, hormones, and enzymes.
- In turn, your digestive tract sends signals to the brain that affect its functioning.
Your gut microbiome is a critical piece of this picture. It’s the collection of microbes — bacteria, viruses, fungi, and parasites — in your intestines, according to Cleveland Clinic. A healthy microbiome is balanced, diverse, and has enough “good” bacteria to balance out the “bad.”
Not only does the gut microbiome play many different roles in your body, but it can also affect your mood. In fact, some bacteria affect the production of mood-regulating neurotransmitters like serotonin. Gut bacteria also produce byproducts, such as short-chain fatty acids (SCFAs), which have anti-inflammatory properties and positive effects on the nervous system. So, researchers believe that gut health may affect neurological conditions and mood disorders.
Probiotics are microorganisms that live in our gut; we can get them from fermented foods like yogurt, as well as from supplements, according to the National Center for Complementary and Integrative Health (NCCIH).
Prebiotics, as research notes, are compounds in certain foods that we can’t fully digest, but our gut bacteria can. They serve as food for beneficial microbes (including probiotics), helping them grow and support gut health.
Some pre- and probiotics have been found to decrease inflammation, control stress response, and promote the secretion of neurotransmitters and SCFAs. Taken together, pre- and probiotics may hold promise as an aid for anxiety, depression, stress, and sleep problems. These good gut bugs may also influence bipolar disorder and treatment.
Bipolar Disorder Is Linked to Differences in Gut Bacteria
Everyone has their own unique gut microbiome. However, the gut composition differs in those with bipolar disorder compared with those without, notes a review published in the journal Molecular Psychiatry. This suggests that gut health may be one factor in the development of bipolar — in fact, the microbiome may even differ with the type of bipolar disorder a person has.
There are a couple of key differences to note, as the research above indicates. First, those with bipolar tend to have less diversity in their gut microorganisms, and their bacterial composition differs from that of other groups.
Secondly, some types of bacteria overlap in bipolar and other psychiatric conditions like major depressive disorder or schizophrenia, while others are unique to bipolar. For example, disruptions in Lachnospiraceae, Prevotellaceae, and Ruminococcaceae (all families of bacteria) have been identified in people with bipolar compared with those without the condition. Researchers have also found an increase in Eggerthella and Lactobacillus, together with a decrease in Coprococcus, across people with bipolar, major depressive disorder, and schizophrenia.
Finally, the Molecular Psychiatry paper also notes that in some studies, people with bipolar disorder showed a lower Bifidobacteria-to-Enterobacteriaceae ratio, along with higher levels of:
- Faecalibacterium prausnitzii
- Bacteroides-Prevotella group
- Atopobium cluster
- Enterobacter species (Enterobacter spp.)
- Clostridium Cluster IV
These shifts in gut bacteria may influence brain function in people with bipolar via the gut-brain axis.
Gut Microbes Could One Day Help Diagnose Bipolar
Because the gut microbiome may have a unique signature in bipolar disorder, it may hold clues about whether a person has the condition. Research is early, but there are potential distinguishing features that could help diagnose bipolar disorder one day, or even help distinguish certain subtypes of bipolar from other psychiatric conditions like schizophrenia, according to one study.
The gut microbiota may also help improve bipolar treatment. A review published in the journal Microbiology examined the effects of psychotropic drugs for bipolar disorder on the gut microbiota; it concluded that, in the future, we may be able to use gut microbiota profiles to create personalized treatment plans that maximize the beneficial effects of these drugs and minimize their risks.
Right now, however, the gold standard of bipolar diagnosis remains a physical exam and mental health evaluation. We need additional data from larger studies, the involvement of more diverse patient populations, and an understanding of how medications alter the gut environment before using gut microbes in diagnosis or treatment.
When Gut Health Is Off, Symptoms May Be Harder to Manage
Imbalances in the gut microbiome, lack of microbial diversity, and decreased production of SCFAs may promote inflammation that impacts brain functioning and is associated with bipolar disorder, according to existing research.
There are several mechanisms behind this, notes the Molecular Psychiatry review, such as:
- Harmful bacteria cause oxidative stress.
- Bacterial imbalance promotes immune dysfunction.
- Increased permeability in the lining of the intestines allows bacteria and other harmful substances to “leak” into the bloodstream.
- As these compounds leak, brain cells called microglia (immune cells that influence inflammation and neuroplasticity) get over-activated — particularly in stressful situations — leading to behavioral changes.
- Fewer SCFAs also cause immune cells in the nervous system to overreact, thereby influencing inflammation and neuroplasticity (the brain’s ability to form new connections).
- SCFAs also play a role in appetite and metabolism, so an imbalance in gut bacteria can cause metabolic dysfunction.
These factors, among others, create inflammation in the brain, leading to cognitive impairment, affecting the stress response, and creating poor emotional reactivity. These changes may contribute to typical bipolar symptoms, which include:
- Having unusually high levels of self-esteem
- Being unusually talkative or speaking very fast
- Having racing thoughts
- Being easily distracted
- Feeling restless or constantly on the go
- Needing much less sleep than usual
- Engaging in risky or impulsive actions and decisions
Bipolar Medications Also Affect Your Gut Microbiome
Bipolar medication may improve your gut microbiome. The Microbiology paper reviewed 12 studies and found that some bipolar drugs — such as quetiapine (Seroquel) and lithium — increase the levels of healthy bacteria, thereby improving the diversity of the gut microbiome. Not everyone responds to medication, but among patients taking quetiapine, those whose bipolar depression improved had a gut microbiome more similar to people without known health conditions (compared with nonresponders).
There are downsides, however. According to the review, quetiapine was also associated with an increase in unhealthy bacteria linked to metabolic dysfunction, particularly in females. Another potential harmful effect is the association with antibiotic resistance in the gut, meaning that there could be long-term health risks associated with these medications.
Probiotics Show Promise, but Research Is Early
Your gut is home to trillions of tiny microorganisms — that’s a wildly complex world, especially when we’re talking about probiotics for bipolar disorder.
Early clues look encouraging. A systematic review of five small studies found that adding probiotics to standard bipolar treatment was associated with reduced manic symptoms in many participants and lower rates of rehospitalization after a manic episode. Depression and anxiety symptoms showed little to no clear improvement in these studies, though.
In terms of cognitive effects, a small pilot study in relatively stable people with bipolar disorder found that a three‑month probiotic regimen improved attention and thinking speed on standardized tests, with some gains in executive function over time. Other work in mixed mood‑disorder samples has also linked probiotics to modest cognitive benefits, such as better verbal memory, but these trials were limited by small sample sizes and sometimes lacked control groups.
There are many strains of bacteria available in probiotics. The most common ones used in the studies above were:
- Lactobacillus
- Bifidobacterium
- Sometimes mixed with Streptococcus, Enterococcus, Bacillus, or Escherichia
Safety, Precautions, and Next Steps
Probiotics are generally well tolerated in otherwise healthy people, with side effects typically limited to mild gastrointestinal symptoms (such as gas or bloating). However, they’re not appropriate for everyone. People who are seriously ill or immunocompromised should avoid them unless a clinician specifically recommends them, as rare complications have been reported.
A key limitation is the lack of a standardized, evidence-based “best” protocol plan for bipolar symptoms yet. Researchers still don’t know which strains are most helpful, the ideal dose (including CFUs), how long to take them, or how probiotics may interact with psychiatric medications or antibiotics.
If you’re interested in taking probiotics, speak to your healthcare provider. Things you could ask them include:
- Do you think probiotics would benefit me?
- Can we fit probiotics into my current treatment plan?
- What specific strains would you recommend?
- What dose should I take, or how many colony-forming units (CFUs)?
- How can we measure progress and see if probiotics are making a difference in my health and mood?
FAQ:
Are certain probiotic strains better for mood?
Research is still early, but some studies suggest that certain Lactobacillus and Bifidobacterium strains may play a role in mood and stress‑related symptoms. More research is needed before clear, strain‑specific recommendations can be made.
Do I need to take supplements, or can food help too?
Fermented foods like yogurt, kefir, sauerkraut, and kimchi naturally contain probiotics. A balanced diet with fiber and prebiotics (foods that feed healthy bacteria) can also support gut health.
Are probiotics safe to try if I have bipolar disorder?
Probiotics are generally considered safe for most people, including those with bipolar disorder, when used as adjunctive support alongside standard treatment. However, you should consult your provider before starting, especially if you have a weakened immune system, are critically ill, or have other complex medical conditions.
How long does it take to notice a difference?
There is limited research on probiotics in bipolar treatment. One study in people with bipolar or schizophrenia-spectrum disorders found benefit to cognition and gastrointestinal health after three months, and another study saw a benefit of self-rated depressive symptoms after 30 days. Talk to your doctor about realistic expectations and what would count as a meaningful improvement for you.
Editorial Sources and Fact-Checking
- Ansari F et al. The Role of Probiotics and Prebiotics in Modulating the Gut-Brain Axis. Frontiers in Nutrition. July 26, 2023.
- Gut Microbiome. Cleveland Clinic. August 18, 2023.
- Probiotics: Usefulness and Safety. National Center for Complementary and Integrative Health. August 2019.
- Davani-Davari D et al. Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Foods. March 9, 2019.
- Ortega MA et al. Microbiota-Gut-Brain Axis Mechanisms in the Complex Network of Bipolar Disorders: Potential Clinical Implications and Translational Opportunities. Molecular Psychiatry. January 27, 2023.
- Prebiotics: Understanding Their Role in Gut Health. Harvard Health Publishing. May 15, 2024.
- Chen Y et al. Gut Microbial Signatures and Differences in Bipolar Disorder and Schizophrenia of Emerging Adulthood. CNS Neuroscience & Therapeutics. December 5, 2022.
- Bui TA et al. Pharmaco-Psychiatry and Gut Microbiome: A Systematic Review of Effects of Psychotropic Drugs for Bipolar Disorder. Microbiology. June 18, 2025.
- Sublette ME et al. Bipolar Disorder and the Gut Microbiome: A Systematic Review. Bipolar Disorders. September 2021.
- Ahmed N et al. Can Probiotics Reduce Bipolar Symptoms?: A Systematic Review. Personalized Medicine in Psychiatry. July–August 2023.
- Reininghaus EZ et al. The Impact of Probiotic Supplements on Cognitive Parameters in Euthymic Individuals With Bipolar Disorder: A Pilot Study. Neuropsychobiology. September 18, 2018.
- Borkent J et al. Probiotic Formulation for Patients With Bipolar or Schizophrenia Spectrum Disorder: A Double-Blind, Randomized Placebo-Controlled Trial. Schizophrenia Bulletin. November 6, 2024.
- Zhang JZ et al. Adjunct Therapy With Probiotics for Depressive Episodes of Bipolar Disorder Type 1: A Randomized Placebo-Controlled Trial. Journal of Functional Foods. June 2023.
