If you are searching for answers about irritable bowel syndrome (IBS), you are likely asking questions like:
- What causes IBS?
- Is IBS caused by stress or food?
- Why do my GI symptoms persist even when tests are normal?
- Is there an underlying gut problem being missed?
- How do you actually treat the root cause of IBS?
These are reasonable questions. IBS affects roughly 10 percent of the global population and is one of the most common reasons people see a gastroenterologist [1]. Yet many patients are left without a clear explanation for why symptoms continue.
Modern research points to a clear answer.
IBS is caused by a disruption in how the gut and brain communicate, rather than permanent damage to the digestive system [2].
What is the root cause of IBS?
The root cause of IBS is dysregulation of the gut-brain axis, the bidirectional communication system between the digestive tract and the central nervous system [2].
In people with IBS, this system becomes overly sensitive and reactive. Normal digestive processes are misinterpreted as threats, leading to symptoms such as abdominal pain, bloating, diarrhea, constipation, urgency, or alternating bowel habits.
For this reason, IBS is medically classified as a disorder of gut-brain interaction, according to the Rome IV and Rome V diagnostic frameworks [2].
How IBS usually begins
IBS commonly starts after a real physical or biological trigger. Well-documented triggers include:
- A gastrointestinal infection or food poisoning
- Antibiotic use
- Prolonged psychological or physiological stress
- Hormonal changes
- Surgery or acute illness
Post-infectious IBS is a recognized clinical entity, with studies showing that 5 to 30 percent of people develop IBS after an acute GI infection [3].
During these trigger periods, the gut may become inflamed or disrupted. The nervous system adapts by increasing vigilance to protect the body. In some individuals, this heightened sensitivity persists even after the original trigger resolves.
Why IBS symptoms continue after the gut heals
In many IBS patients, standard medical tests show no structural disease. Colonoscopy, blood work, and imaging often come back normal.
This does not mean symptoms are imagined.
Research consistently shows that people with IBS have visceral hypersensitivity, meaning the sensory nerves in the gut respond more strongly to normal stimuli [4]. Ordinary digestion can be perceived as painful or urgent.
At the same time, brain imaging studies demonstrate altered central processing of gut signals in IBS patients [5]. This creates a feedback loop:
- The gut sends amplified signals
- The brain pays increased attention to the gut
- Symptoms become more intense and unpredictable
This loop is considered a core mechanism underlying IBS symptoms.
Is IBS caused by food intolerances?
Food often appears to be the cause of IBS symptoms, but evidence suggests this relationship is indirect.
When the gut-brain axis is sensitized, the act of digestion itself can provoke symptoms. Clinical observations and trials show that:
- The same food may cause symptoms on one day but not another
- Elimination diets often help temporarily but lose effectiveness
- Symptoms worsen during stress, travel, or fatigue
- Symptoms improve during distraction or relaxation
While dietary approaches such as low FODMAP diets can reduce symptoms short-term, long-term restriction may increase gut vigilance and symptom sensitivity if not paired with gut-brain retraining [6].
Food is often a trigger, not the underlying cause.
The role of the nervous system in IBS
IBS is not a psychological condition, but the nervous system plays a central role.
Physiological studies show altered autonomic nervous system function in IBS patients, including changes in vagal tone and stress-response pathways [7]. The body remains in a state of heightened readiness, even in safe conditions.
This response is learned and automatic. It reflects conditioning within the gut-brain axis rather than conscious stress or anxiety.
Once the gut becomes associated with threat, symptoms can occur without tissue damage or disease.
Why IBS tests are normal
Medical evaluation is essential to rule out conditions such as inflammatory bowel disease, celiac disease, thyroid disorders, anemia, or infection.
When these conditions are excluded, ongoing investigation often fails to reveal structural pathology. This aligns with the current scientific understanding of IBS as a functional disorder driven by altered signaling rather than visible damage [2].
Repeated testing can unintentionally reinforce symptom monitoring and fear, which may perpetuate gut-brain dysregulation.
How to treat the root cause of IBS
Because IBS is maintained by dysregulated gut-brain signaling, the most effective treatments target this system directly.
The strongest evidence supports brain-gut therapies, which aim to reduce visceral hypersensitivity and normalize central processing of gut sensations.
Evidence-based brain-gut therapies include:
- Gut-directed hypnotherapy
- Cognitive behavioral therapy (CBT) specifically adapted for IBS
- Exposure-based approaches to food and symptom fear
- Interventions that regulate autonomic nervous system activity
Multiple randomized controlled trials show that gut-directed hypnotherapy and CBT for IBS produce significant symptom improvement, with benefits that persist long after treatment ends [8][9].
How to access brain-gut therapy
Access to brain-gut therapy has expanded significantly.
Specialist clinicians
Some gastroenterology clinics and GI-focused psychologists offer gut-directed hypnotherapy or CBT for IBS. Access varies by region and availability.
Digital programs
Digitally delivered programs like Nerva now provide structured, evidence-based brain-gut therapy at home. Clinical trials have shown that digital brain-gut therapy can be as effective as in-person care for IBS [10].
Referral pathways
Many gastroenterologists can refer patients for psychological therapies once IBS is diagnosed. Asking specifically for gut-directed hypnotherapy or CBT for IBS improves the likelihood of appropriate referral.
It is important to choose therapies explicitly designed for IBS rather than general stress management.
What improvement usually looks like
Improvement in IBS typically occurs gradually.
Patients often notice:
- Reduced pain intensity and urgency
- Fewer and shorter flare-ups
- Improved tolerance to food and stress
- Less fear and monitoring of gut sensations
As the gut-brain system relearns safety, symptoms lose their intensity and frequency.
The bottom line on IBS root causes
For most people, IBS is not caused by a damaged gut, a single food intolerance, or a missed disease.
It is caused by a gut-brain system that learned to stay in threat mode and has not yet relearned regulation.
Addressing that system directly is what leads to lasting improvement.
