Which routes does this communication follow?
Research describes four main routes that complement one another:[1][2]
- Nerve pathways, including the vagus nerve and the extensive nervous network in the gut wall.[4]
- The immune system, which relays inflammatory activity via signalling molecules.[10]
- Hormones, including substances involved in the stress response and in satiety.[2]
- Substances produced by gut bacteria, such as short-chain fatty acids and other metabolites.[1]
What does the research suggest?
Studies describe associations between gut microbiome composition and mood, stress response, cognitive function and certain mental health conditions. These are generally associations found in population studies or findings from animal research; cause and effect have not been demonstrated.[5][8]
In pooled analyses, microbiome-targeted interventions show at most small effects on depressive symptoms, with variable study quality.[6][9]
Gut bacteria may influence processes involved in the availability and regulation of substances that play a role in neurotransmission — for example, by contributing to the conversion of nutrients that serve as building blocks. How strong this influence is in humans, and under which circumstances, is still being investigated.[2][7]
A complex field of research
Mood and cognition are shaped by many factors at once: sleep, medication, lifestyle, social circumstances and genetic predisposition. Within that picture, the microbiome is one factor. This makes it difficult to isolate effects, and explains why study results vary.[7][8]
Medical nuance
A gut microbiome analysis does not provide a diagnosis and cannot establish or rule out psychological or psychiatric conditions. If you are experiencing symptoms in this area, assessment by your GP or treating clinician is the first step.
Further reading: back to the knowledge base, gut microbiome test, Personal programme — 1 year or an introductory consultation with the doctor.
Science gives us ever more data. But its meaning starts with the person.
A doctor looks not only at what is measurable, but also listens to what someone experiences.
Scientific references
The information on this page is based on recent scientific literature. Below is a selection of key review articles and systematic reviews on the gut-brain axis. These publications form an important basis for current knowledge about communication between the gut microbiome and the brain. Because this field is developing rapidly, new insights are added to this knowledge base regularly.
Reference 1
The gut microbiota–brain axis in behaviour and brain disorders
Nature Reviews Microbiology · 2021 · Narrative review
Reference 2
The microbiota–gut–brain axis
Physiological Reviews · 2019 · Review
Reference 3
The brain–gut–microbiome axis
Cellular and Molecular Gastroenterology and Hepatology · 2018 · Review
Reference 4
The Gut-Brain Axis: Interactions Between Enteric Microbiota, Central and Enteric Nervous Systems
Annals of Gastroenterology · 2015 · Narrative review
Reference 5
Gut microbiota and major depressive disorder: A systematic review
Journal of Affective Disorders · 2020 · Systematic review
Reference 6
Effects of microbiota-targeted interventions on depressive symptoms: Systematic review and meta-analysis
Neuroscience & Biobehavioral Reviews · 2019 · Meta-analysis
Reference 7
Brain–gut–microbiota axis in depression: A historical overview and future directions
Brain Research Bulletin · 2022 · Narrative review
Reference 8
Gut microbiota and mental health: A systematic review
Neuroscience & Biobehavioral Reviews · 2024 · Systematic review
Reference 9
Psychobiotics and the Microbiota–Gut–Brain Axis
Trends in Neurosciences · 2016 · Narrative review
Reference 10
Microbiota–gut–brain axis and neurological disorders
Journal of Neuroinflammation · 2020 · Review
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