The Connection Between Gut Health and Mood

The gut is often referred to as the “second brain.” This is because the gut and the brain are constantly communicating, and the health of one can significantly impact the other. An emerging body of research now points to a strong connection between gut health and mood.

The trillions of microorganisms that inhabit the gut, collectively known as the gut microbiome, may influence mental health and mood-related conditions like anxiety, depression, and autism spectrum disorder. The gut microbiome interacts closely with the brain via what’s known as the gut-brain axis.

In this comprehensive article, we’ll explore the evidence for the gut-brain connection, how gut health impacts mental wellbeing, and practical steps you can take to optimize your microbiome for better mood.

    The Gut-Brain Connection

    The gastrointestinal system has an extensive network of neurons that enable complex communication between the gut and the brain. This is called the gut-brain axis.

     The Vagus Nerve

    The vagus nerve, the longest cranial nerve, connects the brain stem to many internal organs including the heart, lungs, and digestive tract. This nerve is a key player in the gut-brain axis, facilitating bidirectional communication between the GI system and brain.

    Substances produced in the gut can travel via the vagus nerve to directly impact mood and mental state. Meanwhile, the central nervous system releases chemicals that influence gut function. Stress, for example, can disrupt normal gastric activity.

     The Immune System

    The gut is also in close contact with the body’s major immune hubs. Around 70% of the immune system resides in the gastrointestinal tract. When gut health suffers, so does immune activity. Chronic low-grade inflammation in the body is believed to contribute to depression and other mood issues.


    Finally, the gut microbiome produces many of the same neurotransmitters found in the brain, including serotonin, dopamine, and gamma-aminobutyric acid (GABA). These chemicals can enter general circulation and influence brain function and mental health.

    Taken together, these systems create a vast communication network between the gut and the brain. Disruptions anywhere along this axis may potentially impact psychological health and wellbeing.

    The Gut Microbiome and Mental Health

    The collection of organisms inhabiting the digestive tract, known as the gut microbiome, is integral for every aspect of health. Trillions of bacteria, viruses, fungi and other microbes live symbiotically in the gastrointestinal system.

    The gut microbiome begins forming right after birth and develops rapidly during the first few years of life. After that, the population typically remains relatively stable throughout adulthood. Diet, medications, illness, stress, aging, and other factors can negatively impact the composition of the gut microbiome.

    Benefits of a Healthy Microbiome

    A healthy microbiome contains many different species of microbes. In a balanced state of diverse species called eubiosis, these “good bacteria” keep each other in check and perform vital functions like:

    • Digesting nutrients and producing vitamins
    • Regulating immune activity and inflammation
    • Communicating with the gut-brain axis
    • Producing mood-influencing neurotransmitters
    Consequences of Dysbiosis

    When the microbiome is lacking in diversity, it enters a state called dysbiosis. Certain species may grow unchecked, while the numbers of beneficial bacteria dwindle. Dysbiosis along the gut-brain axis is thought to contribute to psychiatric conditions including anxiety, depression, OCD, autism, and more.

    Evidence for a Microbiome-Mood Connection

    • Multiple scientific studies have uncovered links between gastrointestinal issues, an unbalanced microbiome, and mental health disorders:
    • People with major depressive disorder frequently have gastrointestinal symptoms and a higher incidence of dysbiosis.
    • Rodent studies show transplanting fecal matter from depressed patients causes depressive behaviors in formerly healthy mice. Transplanting healthy fecal matter into mice with depressive symptoms can improve their mood.
    • Germ-free mice raised in sterile conditions and lacking a microbiome often exhibit anxiety and hyperactivity compared to normal mice.
    • Individuals on the autism spectrum are much more likely to experience chronic GI complications. Some studies indicate improving gut health through diet changes and probiotic supplements may also improve autistic behaviors.
    • Mice models of neurodevelopmental disorders like autism display both behavioral symptoms and distinctive gut microbiome profiles compared to controls.
    • Probiotic supplements containing beneficial bacteria like Bifidobacterium and Lactobacillus reduce anxiety and depressive symptoms in both animals and humans.

    The reasons behind the gut-mood connection are still being unraveled. However, factors like inflammation, immune dysfunction, microbiome-produced neurotransmitters, and vagus nerve stimulation may be involved.

    Ongoing communication along the gut-brain axis is necessary for optimal mental health. When the gut microbiome falls into imbalance, it appears this intricate communication network can be disrupted in ways that give rise to psychiatric issues.

    How Poor Gut Health Can Contribute to Mood Disorders

    Dysbiosis along the gut-brain axis may contribute to mental health disorders through several mechanisms:


    A healthy helps regulate immune responses and prevents uncontrolled inflammation in the body. Without enough beneficial bacteria to keep them in check, certain microorganisms can trigger chronic low-grade inflammation.

    Inflammation is a recognized factor in depression, anxiety, and other mood disorders. Pro-inflammatory cytokines produced during inflammatory responses can travel through the bloodstream and cross the blood-brain barrier to directly impact mood and cognition.

    Bacterial Overgrowth

    With dysbiosis, populations of certain microbes like Candida yeasts can expand far beyond normal levels in the gut. Bacterial overgrowth allows microorganisms and their neurotoxic metabolites to enter the bloodstream.

    Once in circulation these compounds are able to move through the permeable regions of the blood-brain barrier and influence neurotransmission. This may negatively impact mood and behavior.

    Neurotransmitter Disruption

    The gut microbiome naturally produces some of the same neurotransmitters found in the brain, like serotonin, GABA, and dopamine. Shifts in microbial populations may alter neurotransmitter levels, preventing stable mood regulation.

    Too little beneficial bacteria may result in inadequate mood-stabilizing neurotransmitter levels. Meanwhile, unchecked populations of other microbes may produce an excess of chemicals that can interfere with brain signaling.

    Vagus Nerve Dysfunction

    As mentioned, the vagus nerve is a main route of communication between the gut and brain. Vagus nerve stimulation is being explored as a potential therapeutic approach for treatment-resistant depression.

    Gut dysbiosis and inflammation likely interfere with proper functioning of the vagus nerve. Disruption along this critical gut-brain communication channel could worsen mood issues.

    Mental Health Consequences of Dysbiosis

    An unhealthy gut microbiome is believed to play a role in many different psychiatric conditions:

    Anxiety and Depression

    Gastrointestinal dysfunction and inflammation are hallmarks of both anxiety and major depression. The dysbiosis seen in these mood disorders decreases beneficial gut microbes involved in neurotransmitter synthesis.

    Antibiotics, poor diet, and chronic stress - all known risk factors for microbiome imbalance - are also associated with higher rates of clinical anxiety and depression. Supplementing with probiotic strains of Bifidobacterium and Lactobacillus has been shown to improve mood and reduce symptoms in those with depressive and anxious dispositions.

    Autism Spectrum Disorder

    Up to 90% of autistic individuals suffer from chronic gut issues like constipation, diarrhea, abdominal pain, and intestinal permeability. Autistic children frequently have dysbiosis characterized by lower microbiome diversity.

    Introducing healthy bacteria through probiotic foods, fecal transplants, or supplements has improved both GI and behavioral symptoms in some studies. Correcting dysbiosis may ameliorate autism severity by reducing inflammation, regulating neurotransmitters, and restoring gut-brain communication.


    Children with ADHD appear to have a distinct gut microbiome profile compared to those without the disorder. ADHD is also associated with higher rates of GI symptoms.

    Animal studies suggest introducing beneficial bacteria like Lactobacillus rhamnosus may reduce hyperactivity and inattention - hallmark symptoms of ADHD. Improving the gut microbiome early in life could help prevent a hyperactive immune system that contributes to many cases of ADHD.

    Obsessive-Compulsive Disorder

    OCD patients frequently have poor gut health including more GI symptoms, higher rates of IBS, and an altered microbiome. OCD behaviors and symptoms are also exacerbated in mice that lack a microbiome or have GI inflammation


    Schizophrenia is accompanied by greater likelihood of gut complications like IBS and intestinal permeability. Germ-free mice also develop behaviors mimicking schizophrenia at higher rates than mice with normal microbiomes.

    The microbiomes of schizophrenic individuals show less diversity and anti-inflammatory short-chain fatty acids compared to healthy controls. Targeting dysbiosis through probiotics may help regulate gut-brain communication deficits underlying schizophrenia.

    As researchers learn more about the mechanisms involved, treatments targeting restoration of the gut microbiome may become an adjunct or even alternative option for certain mental health disorders.

    Optimizing Gut Health for Better Mood

    Supporting a healthy balanced gut microbiome is key for optimal communication along the gut-brain axis. Here are some lifestyle approaches to improve your gut health and mood:


    Diet is one of the biggest determinants of gut microbiome composition. An unhealthy diet high in fat, sugar, and processed foods contributes significantly to dysbiosis and inflammation. Conversely, consuming a diverse diet rich in whole foods fosters the growth of beneficial gut bacteria.

    Several dietary measures can help optimize the gut-brain axis:

    • Eat more fiber - aim for 25-30g daily
    • Focus on fermented foods like yogurt, kimchi, and sauerkraut
    • Eat prebiotic foods like garlic, onions, leeks, asparagus
    • Increase polyphenols from tea, coffee, wine, dark chocolate
    • Limit saturated fats
    • Reduce refined carbs and sugar
    • Avoid artificial sweeteners and additives
    • Stay hydrated with water and hydrating beverages

    Exercise and Stress Reduction

    Along with a healthy diet, lifestyle factors like exercise and stress management also support a robust, diverse microbiome.

    Regular physical activity boosts gut motility, lowers inflammation, and reduces stress hormones. Meanwhile, chronic stress has detrimental effects on the gut microbiome diversity and function.

    Relaxation practices like yoga, mindfulness meditation, deep breathing, and adequate sleep counteract stress to promote a healthy microbiome.

    Probiotics and Supplements

    Probiotic supplements containing species like Lactobacillus and Bifidobacterium have shown efficacy for improving mood disorders. Prebiotics provide nourishment for existing microbes, while supplements combining probiotics and prebiotics may have synergistic effects.

    Some other beneficial supplements include turmeric, omega-3s, zinc, magnesium, and vitamin D. Focus on getting these nutrients from whole food sources before looking to supplements.

    Pros and Cons of Targeting the Gut Microbiome for Mental Health

    Modulating the gut microbiome shows promise as an adjunct or alternative treatment approach for certain psychiatric conditions, but there are also some limitations:


    May help reduce systemic inflammation underlying mood disorders

    Provides option for patients resistant to medication or psychotherapy

    Relatively safe and low risk compared to psychiatric meds

    Psychobiotic supplements are accessible and easy to implement

    Also improves broader markers of health like immunity and digestion


    Mechanisms not yet fully understood

    Difficult to study causal relationships in humans

    Psychobiotic supplements not well regulated or standardized

    Benefits likely dependent on continued use

    Not a quick fix; takes time to reshape microbiome

    Outcomes can vary greatly between individuals

    Diet and lifestyle changes may be difficult to adhere to

    While regulating the gut microbiome shows potential for managing mood disorders, more research is still needed to confirm efficacy and safety, especially long-term. It should be considered an adjunct, not replacement, for conventional treatment under medical supervision.

    Conclusion & Summary 

    • Bidirectional communication along the gut-brain axis is important for mental health. Disruptions to this pathway may contribute to mood disorders.
    • Gut microbiome balance regulates immunity, neurotransmitters, and GI function in ways that impact the brain and mood. Dysbiosis is linked to increased risk of psychiatric issues.
    • Diet, exercise, stress management, probiotics, and other lifestyle measures can help optimize the gut microbiome to support mental wellbeing.
    • Targeting the gut-brain connection shows promise for improving inflammation, brain signaling, and other factors underlying neuropsychiatric conditions. More research is still needed to validate effectiveness and safety.
    • While regulating the microbiome may benefit some individuals, it should be considered a complementary approach to managing mental health, not a replacement for conventional treatment.
    • Ongoing study of how the gut microbiome influences the brain will continue unraveling this important bidirectional relationship and how it can be leveraged to support both gastrointestinal and psychological wellbeing.


    How does the gut microbiome communicate with the brain?

    The gut microbiome interacts with the brain via the gut-brain axis, which includes the vagus nerve, immune signaling, and metabolic pathways. Gut microbes can produce neurotransmitters and other metabolites that enter circulation and influence the brain.

    What evidence links gut health to mood?

    Studies show people with mood disorders frequently have GI issues and dysbiosis. Animal studies demonstrate introducing unhealthy gut bacteria can cause anxious and depressive behaviors. Probiotics have reduced symptoms in humans. These suggest disrupting the gut microbiome negatively impacts mood.

    Can probiotics improve mental health conditions?

    Some clinical studies have found certain probiotic strains from genera like Lactobacillus and Bifidobacterium can improve anxiety, depression, and obsessive compulsive symptoms. However, outcomes vary widely between individuals. More research is still needed.

    What lifestyle changes support a healthy microbiome?

    Eating a fiber-rich anti-inflammatory diet, managing stress levels, exercising regularly, getting enough sleep, staying hydrated, and avoiding overuse of medications like antibiotics help maintain a diverse gut microbiome ideal for whole-body health.

    Should I take psychobiotic supplements for depression?

    Speak to your doctor before starting psychobiotic supplements, especially if you have underlying health conditions or take medications. While regulating the microbiome shows promise for supporting mental health, supplements are not a replacement for other treatments. Lifestyle approaches should be focused on first.

    Does C-section impact the infant gut microbiome and mood?

    Babies born via C-section lack early exposure to maternal bacteria. This can alter the infant gut microbiome in ways associated with increased risks of immune dysfunction, obesity, and psychiatric issues later in life compared to vaginally-delivered babies.

    Can antibiotics cause mood changes?

    Yes, antibiotics can negatively impact the gut microbiome which communicates with the brain. This disruption along the gut-brain axis could potentially contribute to psychological symptoms like anxiety, depression, and confusion in some people. Probiotics may help counteract.

    Is there a gut-brain diet to follow?

    Diets high in diverse fiber sources, fermented foods, prebiotics, and polyphenols support microbiome and brain health. Limiting sugar, refined carbs, saturated fats, and artificial additives also helps. An anti-inflammatory Mediterranean-style diet rich in plants optimizes the gut environment and microbiome.

    Are fecal transplants effective for mental health conditions?

    While research is very limited, some small studies have found fecal microbiota transplantation improved symptoms of depression, anxiety, and autism spectrum disorder. Much more study is still needed to confirm efficacy and safety. Speak to your doctor before considering.

    Key Takeaways and Action Steps

    The gut microbiome interacts closely with the brain via the gut-brain axis and can influence mood and mental health.

    Supporting gut health through diet, lifestyle, supplements, and other means may help improve some psychiatric conditions including anxiety, depression, and OCD.

    Talk to your healthcare provider before making major changes to your mental health treatment. Psychobiotic approaches should complement, not replace, conventional therapy.

    Eat more fiber, fermented foods, and polyphenol-rich plant foods to support microbiome diversity. Limit sugar, refined carbs, saturated fats, and artificial additives.

    Manage stress levels through yoga, meditation, deep breathing, and other relaxing activities that calm the mind-gut connection.

    Take probiotic supplements only after discussion with your doctor, and do not expect them to be a cure-all.

    Get regular exercise, prioritize sleep, stay hydrated, and support all aspects of a healthy lifestyle to foster a robust microbiome.

    Be patient; it takes time to reshape your gut microbiome. Stick with psychobiotic interventions for at least 2-3 months to assess effects.

    Keep an open dialogue with your healthcare providers about any lifestyle changes, natural approaches, or supplements you want to try for supporting mental health through the gut-brain axis.