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Gut-brain axis disorders
Gut-brain axis disorders, which doctors now call disorders of gut-brain interaction, are conditions in which the gut and the brain do not signal to each other smoothly. They cause real symptoms, such as pain, bloating, nausea, fullness and a changed bowel habit, while endoscopy, scans and blood tests are normal. Irritable bowel syndrome and functional dyspepsia are the commonest. They are diagnosed from the pattern of symptoms and treated on both sides of the connection: the gut and the nervous system.
At a glance
What they are
Disorders of how the gut and the brain signal to each other. The gut itself is structurally normal.
Common examples
IBS, functional dyspepsia, functional bloating, constipation or diarrhoea, and cyclic vomiting.
How they are confirmed
From the pattern of symptoms, with a limited set of tests to rule out other disease.
How they are treated
Food changes, medicines for the gut, low-dose medicines that calm gut nerves, and brain-gut therapies.
What are the signs of a gut-brain axis disorder?
Upper gut
- Uncomfortable fullness after an ordinary meal
- Feeling full after a few mouthfuls
- Pain or burning in the upper abdomen
- Nausea and belching
Lower gut
- Abdominal pain that changes with passing stool
- Bloating that builds through the day
- Constipation, loose stools or both
- Urgency, or a feeling of incomplete emptying
What they have in common
- Symptoms for months, which come and go
- Normal endoscopy, scans and blood tests
- Worse after a gut infection, with poor sleep or under stress
- Often more than one of these conditions in the same person
These are not signs of a gut-brain disorder
See a doctor promptly if you have:
- Blood in the stool, or black stools
- Weight loss you cannot explain
- Difficulty swallowing, or vomiting that will not stop
- Fever, or symptoms that wake you from sleep
- A low blood count (anaemia)
- Symptoms that began after the age of 50
- A close relative with bowel cancer, colitis or coeliac disease
What it is
What is happening inside?
The gut has its own nervous system, which is in constant two-way conversation with the brain through the vagus nerve, hormones and the immune system. Gut bacteria take part in this conversation.
In these disorders, one or more of the following has changed:
- Sensitivity: the nerves of the gut signal pain or fullness at normal amounts of food, gas and stretch.
- Movement: the gut moves too fast, too slowly or out of rhythm.
- The lining and its immune cells: there can be mild changes that a routine biopsy does not report.
- Gut bacteria: the community is altered, often after an infection or antibiotics.
- Processing in the brain: signals from the gut are amplified, especially under stress or with poor sleep.
The connection runs in both directions. In a 12-year study of about 1,000 adults, people with anxiety at the start were more likely to develop a gut disorder later, and people with a gut disorder at the start were more likely to develop anxiety or low mood later.
These disorders are common. In a worldwide study of more than 73,000 adults in 33 countries, about four in ten of those surveyed online met the criteria for at least one of them. In the countries surveyed by household interview, which included India, the figure was about two in ten.
Which conditions belong to this group?
| Condition | Main symptoms |
|---|---|
| Irritable bowel syndrome | Abdominal pain linked to bowel movements, with diarrhoea, constipation or both |
| Functional dyspepsia | Fullness after meals, early fullness, upper abdominal pain or burning |
| Functional bloating | Bloating or visible swelling as the main complaint |
| Functional constipation | Hard or infrequent stools without much pain |
| Functional diarrhoea | Loose stools without much pain |
| Functional heartburn | Burning behind the breastbone with normal acid levels on a pH study |
| Cyclic vomiting syndrome | Bouts of intense vomiting, separated by weeks of feeling well |
| Centrally mediated abdominal pain | Constant or near-constant pain, not linked to eating or bowel movements |
Why it happens
The causes I look for
Other conditions can look like a gut-brain disorder or sit alongside one. Finding them changes the treatment.
A past gut infection
About one in ten people develop IBS after a bout of infectious diarrhoea. The symptoms can last for months or years after the infection has cleared.
Bacterial overgrowth and food intolerances
SIBO and intolerance to lactose or fructose are found with a breath test.
Coeliac disease, thyroid disease and H. pylori
Each is screened for with a simple test.
Medicines
Painkillers, some diabetes medicines, antibiotics, iron and strong pain medicines of the opioid group all affect the gut.
Sleep, stress and mood
These set the sensitivity of the gut’s nerves. Asking about them is part of a complete assessment. It does not mean that the symptoms are imagined.
Pelvic floor problems
In long-standing constipation, the muscles that should relax during a bowel movement tighten instead.
How I find out
Which test answers which question?
The diagnosis is made from the pattern of symptoms, using internationally agreed criteria. Tests are few, and each is chosen to exclude a specific condition.
Blood and stool tests
It tells us: Whether there is anaemia, inflammation, coeliac disease, a thyroid problem or a gut infection.
When I use it: At the first visit.
Upper GI endoscopy
It tells us: That the food pipe, stomach and duodenum are healthy, and whether H. pylori is present.
When I use it: With upper gut symptoms and warning signs, or symptoms that have not responded to treatment.
Colonoscopy
It tells us: That the bowel lining is healthy.
When I use it: With warning signs, or when screening is due for your age.
Hydrogen breath test
It tells us: Whether bacterial overgrowth or a sugar intolerance is contributing.
When I use it: With marked bloating, gas and loose stools.
Manometry and pH monitoring
It tells us: How the food pipe or the pelvic floor muscles work, and whether acid reflux is truly present.
When I use it: When swallowing, heartburn or constipation does not fit the usual pattern.
Heart rate variability
It tells us: The balance between the stress and rest branches of the nervous system.
When I use it: As a starting point for breathing and biofeedback work.
Treatment
How are gut-brain axis disorders treated?
A diagnosis you can use
A clear name for the condition, an explanation of why the tests are normal, and the knowledge that it does not damage the gut. This alone reduces repeated testing and worry.
Food
- Regular meals, eaten without hurry
- Soluble fibre such as isabgol (psyllium), started low and increased slowly
- Less caffeine, alcohol, fizzy drinks and very fatty food
- A low FODMAP diet for a limited period, guided by a dietitian, with step-by-step reintroduction
See the low FODMAP diet.
Medicines for the gut
Chosen for the main symptom: antispasmodics for cramps, laxatives for constipation, medicines that slow the bowel for diarrhoea, and acid-reducing or motility medicines for upper gut symptoms.
Low-dose medicines that calm gut nerves
Certain antidepressant medicines, at doses lower than those used for depression, reduce pain signals from the gut. In a trial of 463 people with IBS, a low-dose medicine of this kind worked better than a dummy tablet over six months.
Brain-gut therapies
Cognitive behavioural therapy and gut-directed hypnotherapy have the largest body of evidence among psychological treatments for IBS. Both are available through my centre, alongside breathing practice, HRV biofeedback, yoga therapy and sleep correction, taught by a trained team. See gut-directed hypnotherapy and CBT and nervous-system retraining for IBS.
Is surgery ever needed?
No. These disorders are never treated with an operation. Part of my role as a surgeon is to protect you from one you do not need.
Root-cause care
The integrative view: what else I look at
- Gut bacteria: symptoms that began after an infection or repeated antibiotics point to a disturbed gut community. See microbiome restoration.
- The tone of the nervous system: slow breathing, HRV biofeedback and, for selected patients, non-invasive vagus nerve stimulation as an add-on.
- Sleep and daily rhythm: regular hours and an early, lighter dinner. See how sleep affects the gut.
- Nutrition: low vitamin B12, vitamin D or iron, and swings in blood sugar.
- Movement: regular physical activity improved IBS symptoms in a randomised trial.
The Gut Health Program brings these together over three or six months.
From my practice
In many of the people I treat, gut symptoms and anxiety or low mood have risen and fallen together for years. Often the gut trouble goes back to childhood. I treat the two sides at the same time and not one after the other.
The course I usually see is this. In the first month there is some relief, mostly less bloating and more energy. In the second and third months the gut and the mood both improve clearly. Between the fourth and the sixth month the change becomes steadier.
This is what I observe in my own patients. It is not a promise for any one person, and it has not been tested in a trial. I wrote about it in my chapter of the book The Missing Links.
Recovery
What should I expect?
| When | What happens |
|---|---|
| First visit | A full history, a limited set of tests, and a clear explanation of the diagnosis. |
| Weeks 2 to 8 | Food changes and the first medicines, matched to your main symptom. |
| Months 2 to 3 | If symptoms persist, a nerve-calming medicine or a brain-gut therapy is added. |
| Long term | Symptoms can flare with infections, travel or stress. You will have a plan for those times. |
Questions patients ask me about gut-brain axis disorders
Does “gut-brain disorder” mean it is all in my head?
No. These are disorders of nerve signalling between the gut and the brain, with measurable changes in gut sensitivity and movement. Stress can worsen them, as it worsens asthma or high blood pressure.
Is this the same as IBS?
IBS is one condition in this group, and the commonest. Functional dyspepsia, functional constipation and several others belong to the same group.
Why are all my tests normal?
Endoscopy, scans and blood tests look for damage: ulcers, inflammation, growths. In these disorders the structure is normal and the function is not. See normal reports but still unwell.
Can anxiety cause stomach problems?
Yes. The gut and the brain share nerves and chemical messengers, so anxiety can speed up or slow down the gut and make it more sensitive. The same holds in the other direction.
Will I need an antidepressant?
Not everyone does. When pain persists despite other treatment, a low dose of one of these medicines is used for its effect on gut nerves, not for depression.
Can the gut-brain axis be “reset”?
There is no single reset. What helps is steady work on several fronts: food, sleep, breathing practice, movement and, where needed, medicines or therapy.
Do gut-brain disorders go away?
In many people symptoms settle for long periods, and some become free of them. In others they return from time to time. The aim is good control and the confidence to manage a flare.
Sources
This page is written for patients and is based on the guidelines and studies below. It is for education and does not replace a consultation.
- Rome IV overview of disorders of gut-brain interaction. Drossman DA. Gastroenterology. 2016. PubMed 27144617
- Rome Foundation global study of how common gut-brain interaction disorders are. Sperber AD et al. Gastroenterology. 2021. PubMed 32294476
- Twelve-year study showing the brain-gut pathway runs in both directions. Koloski NA et al. Gut. 2012. PubMed 22234979
- Rome Foundation report on irritable bowel syndrome that follows a gut infection. Barbara G et al. Gastroenterology. 2019. PubMed 30009817
- American College of Gastroenterology guideline on irritable bowel syndrome. Lacy BE et al. Am J Gastroenterol. 2021. doi:10.14309/ajg.0000000000001036
- Rome IV criteria for bowel disorders. Lacy BE et al. Gastroenterology. 2016. PubMed 27144627
- Rome IV criteria for gastroduodenal disorders. Stanghellini V et al. Gastroenterology. 2016. PubMed 27147122
- Rome Foundation report on neuromodulators for gut-brain interaction disorders. Drossman DA et al. Gastroenterology. 2018. PubMed 29274869
- Trial of a low-dose tricyclic medicine for irritable bowel syndrome in primary care. Ford AC et al. Lancet. 2023. PubMed 37858323
- Network meta-analysis of psychological therapies for irritable bowel syndrome. Black CJ et al. Gut. 2020. PubMed 32276950
- Rome Foundation report on brain-gut behaviour therapies. Keefer L et al. Gastroenterology. 2022. PubMed 34529986
- Trial of physical activity for irritable bowel syndrome. Johannesson E et al. Am J Gastroenterol. 2011. PubMed 21206488
- Review of the microbiota-gut-brain axis. Cryan JF et al. Physiol Rev. 2019. PubMed 31460832