10 September 2026 · Reviewed by Dr. Silvia Mercado marketing

Gut microbiota and mental health: what we know

Learn what research says about the gut microbiota and mental health, understand the limits of the evidence, and know when to seek professional help.

If you are looking for a reliable explanation of the relationship between the gut microbiota and mental health, it is easy to come across claims that go too far. Probiotics, diets and supplements are often presented as answers for anxiety or depression, although a popular recommendation is not the same as a proven treatment.

The gut microbiota is involved in communication between the gut and the brain through several pathways. But knowing that this connection exists does not mean that a specific alteration in the microbiota causes a mental disorder on its own. The available evidence shows associations and research findings, but it still does not support presenting probiotics or dietary changes as a treatment.

It is important to distinguish what has been observed in people from what comes from animal or laboratory studies. Differences between products, diets, medication and analytical methods must also be taken into account. Taking care with your diet, getting enough rest and seeking professional help when symptoms persist may be reasonable; replacing treatment with a promise about the microbiota is not.

What is the relationship between the gut microbiota and the brain

The gut microbiota and the brain communicate in both directions. This network is known as the gut–brain axis. It is not a direct line between a bacterium and an emotion. It is a set of signals connecting the gut, nervous system, immune system and metabolism.

The gut has its own neural network, the enteric nervous system. It also exchanges signals with the brain through the vagus nerve and other neural pathways. These signals provide information about intestinal movement, distension, pain and the state of the tissue. In turn, the brain can modify intestinal motility, secretion and sensitivity through stress and other emotional states.

The microbiota contributes to this communication indirectly. As bacteria use the available nutrients, they produce metabolites. Some of these can act on intestinal cells, influence the intestinal barrier or modulate signals that reach the nervous system. Their activity also interacts with the immune system, which regulates inflammatory processes and releases signalling molecules.

Diet, sleep, infections, medications and stress can change this environment. That is why detecting a difference in microbiota composition is not enough to identify a cause. The same alteration may be associated with several factors at once, and the relationship can also work in reverse: a person’s health and habits can modify their microbiota.

The gut–brain axis provides a biologically plausible explanation for studying the relationship between the gut microbiota and mental health. It does not show that a specific bacterium causes anxiety or depression. Determining which interventions are helpful requires well-designed clinical studies and reproducible results.

What the evidence says about the microbiota, anxiety and depression

Research has found associations between the gut microbiota and some mental health conditions, including anxiety and depression. In people with these diagnoses, researchers have observed differences in the composition or activity of gut bacteria. But an association does not show that these differences cause the symptoms.

The relationship may work in several directions. Stress, sleep, diet, physical activity, illness or medication can alter the microbiota. At the same time, changes in the gut could influence processes related to inflammation, metabolism or communication with the brain. The same finding may reflect several causes at once.

Studies in people face another challenge: not all of them analyse the microbiota in the same way or compare equivalent populations. Diets, treatments and the methods used to measure anxiety or depression also vary. For this reason, a pattern observed in one group cannot be used to diagnose an individual or predict how they will respond to a food or supplement.

Animal and laboratory studies help explore possible mechanisms. For example, they make it possible to examine whether modifying the microbiota changes certain behaviours or biological signals. However, these findings do not prove that the same intervention treats anxiety or depression in humans. The organism, context and psychological experience are not interchangeable.

The cautious conclusion is clear: there is a plausible relationship that remains under active investigation, but it is not yet possible to say that the gut microbiota alone causes a mental disorder. Nor can a microbiota analysis, diet or probiotic be presented as a diagnostic test or universal treatment.

Probiotics, prebiotics and psychobiotics: what can be said

Probiotics are live microorganisms added to certain foods or supplements. Their effects depend on the strain, the amount administered, how long they are used and the individual’s characteristics. For this reason, simply saying that a product “contains probiotics” is not enough to predict a benefit for mood.

Prebiotics are components used by certain gut microorganisms. They are commonly found in fibre-rich foods, although they are also included in some supplements. They do not work as a direct treatment for anxiety or depression. Their effects depend on the person’s overall diet, digestive tolerance and health context.

The term psychobiotic is used to describe interventions targeting the microbiota that may affect brain function or behaviour. These may include certain probiotics, prebiotics or other strategies. The term does not refer to a single therapy or guarantee a clinical outcome.

Clinical trials have studied specific products and specific groups of people. Their results cannot automatically be applied to every supplement, food or individual. Scientific reviews also point to differences in strains, doses, duration of the interventions, diets, medication and the ways symptoms are measured. This diversity makes it difficult to compare studies and draw a general recommendation.

The cautious conclusion is clear: some products may produce changes in certain symptoms or markers, but the evidence does not support presenting probiotics, prebiotics or psychobiotics as a universal treatment for anxiety, depression or other disorders. Nor does it justify stopping prescribed treatment. If someone wants to try a supplement, it is advisable to discuss it with a healthcare professional and assess its composition, potential interactions and the actual purpose of using it.

How to care for your microbiota without miracle claims

Caring for your gut microbiota does not require buying a supplement or following an extreme diet. The most sensible approach is to maintain sustainable habits and observe how your body responds.

A varied diet provides different types of fibre and avoids relying on a single food. Fruit, vegetables, pulses, nuts, seeds and whole grains can all contribute to this variety. It is also advisable to introduce changes gradually. Increasing fibre too quickly can cause gas, bloating or changes in bowel habits. If someone has a digestive disease, allergies or a restricted diet, they should make these decisions with a healthcare professional.

Rest matters too. Poor sleep can affect wellbeing, appetite and how stress is perceived. Keeping regular schedules and allowing enough time for sleep helps build a more stable routine. Regular physical activity completes this framework. Walking, cycling, swimming or doing another form of exercise that is sustainable for you may benefit your general health and mood.

None of these habits guarantees the prevention or resolution of anxiety, depression or any other mental health disorder. Nor can symptoms reveal what a person’s microbiota is made up of. Diet and exercise support health care; they do not replace a medical or psychological assessment.

Be wary of messages that promise to “repair” the microbiota in a short time, attribute a universal effect to a particular food or recommend stopping a treatment. A reasonable change should be sustainable and should not delay seeking professional help when discomfort is persistent, severe or disabling.

When to seek professional help for anxiety or low mood

Anxiety or low mood warrant professional assessment when they persist, worsen or interfere with daily life. Make an appointment with a doctor, psychologist or psychiatrist if you are finding it difficult to work, study, sleep, eat, maintain relationships or look after yourself. You should also seek help if symptoms take up a large part of your days or are difficult to control.

Do not wait until the distress becomes unbearable. A professional can assess your symptoms, review possible causes, evaluate risk and suggest a care plan. Gut microbiota, diet and supplements cannot rule out other causes or replace this assessment.

Seek urgent help if you experience thoughts of suicide, urges to harm yourself, a plan to do so, a marked loss of contact with reality or an inability to keep yourself safe. If this happens:

Do not stay alone. Ask someone you trust to remain with you.
Move medicines, weapons or other objects you could use to harm yourself out of reach.
Contact the emergency services in your country or go to an emergency department.
Explain directly what is happening: “I am having thoughts of harming myself and I do not feel safe.”
If you are supporting someone else, listen without judging and do not promise to keep the risk secret. Help them contact a healthcare professional.

A conversation about probiotics or dietary changes should not delay care when there is severe distress or danger. Nor should you stop a prescribed treatment without first speaking to the professional who prescribed it. Diet can form part of overall care, but it does not replace the diagnosis or treatment of a mental health disorder.

Frequently asked questions

Can the gut microbiota cause anxiety or depression?

It cannot be said that the gut microbiota alone causes anxiety or depression. Some studies have observed associations between microbiota composition and certain symptoms, but an association does not prove causality. Mental health depends on multiple factors and requires clinical assessment.

Do probiotics improve mental health?

Some trials have investigated whether certain probiotics can influence specific symptoms, but the results do not support presenting these products as a universal treatment. Their effects depend on the strain, dose, duration and individual. A probiotic does not replace psychological, psychiatric or medical care.

Which foods benefit the gut microbiota?

A varied diet is usually a more sensible option than an extreme diet or one based on a single product. Fruit, vegetables, pulses, whole grains and other fibre-rich foods can form part of this dietary pattern, depending on each person’s needs. No single food can cure anxiety or depression.

Should I stop my treatment if I change my diet or take probiotics?

No. Changing your diet or taking a supplement is not a reason to stop or modify a prescribed treatment. Speak to a healthcare professional before introducing a product, especially if you take medication or have a medical condition. If your symptoms worsen or interfere with your daily life, seek a healthcare assessment.

Sources

Other related tests

Metabolómica funcional
Cuantificación por GC-MS de los ácidos grasos de cadena corta (butirato, propionato, acetato) para evaluar la actividad funcional real de la microbiota intestinal.
Microbiota Esencial
Análisis metagenómico clínico dirigido a la evaluación cuantitativa y cualitativa de los 150 microorganismos intestinales más relevantes para la salud humana.
Calprotectina fecal
Marcador validado de inflamación de la mucosa intestinal que ayuda a diferenciar la patología orgánica del trastorno funcional y a orientar la indicación de colonoscopia.

See the full catalogue