Opening your Brain to Irritable Bowel Syndrome - the Gut is only half the problem

A good explanation goes a long way

“You just have IBS”…

Have you been told this? If so, how did it make you feel?

Did you feel reassured that you don’t have anything sinister, or hopeless that you are stuck with these symptoms for life?

Unlike conditions like Crohn's Disease or Ulcerative Colitis, IBS does not show visible damage during a gastroscopy or colonoscopy.

This does not mean your pain is not real – it absolutely is…

Therefore, we need to look deeper at how your gut functions rather than its structure.

The aim of this article is to equip you with a deeper understanding of this condition.

The first step to recovery (in my opinion) is understanding what's actually happening inside your gut.

The truth is, Irritable Bowel Syndrome (IBS) is common, affecting 5-15% of the total population….so you’re certainly not alone.

IBS is a disorder of bowel function rather than structure. Truth is, there is likely an organic basis underlying the symptoms for many patients which modern science is currently unable to explain.

What we currently know is the gut and brain communicate to each other via the enteric nervous system.

In some patients there is usually a trigger….this can be physiological, like gastroenteritis or a psychological insult such as trauma.

This leads to abnormal communication between the gut and brain…

This is important because the enteric system controls the motility of the bowel (i.e. how fast content moves through the bowel) and pain stimuli.

What’s the end result? Altered bowel habits and unwanted abdominal pain, otherwise known as visceral hypersensitivity. The brain then processes this pain into thinking normal physiological stimuli is painful, therefore the symptoms become chronic.

Irritable Bowel Syndrome is sadly chronic in 2/3rds of patients.

But this can’t be IBS….my symptoms are way too severe

The first question to ask is, have you had the basics? This includes:

• Blood tests including coeliac screen and thyroid function

• A faecal calprotectin (this checks for inflammation within the stool, which suggests an angry, inflamed bowel)

• An ultrasound to exclude any obvious structural issues

If your answer is "yes and all tests were normal" and your symptoms include generalised, cramping abdominal pain (with or without bloating) combined with altered bowel habits or constipation, evidence suggests the likelihood of additional investigations discovering a new condition is very low.

Nevertheless, the symptoms can be severe…sometimes even more severe than a patient with an organic condition (such as Crohn’s disease) with a similar negative effect on quality of life.

When in Rome…

In 1988 a bunch of gastroenterologists met up in Italy to create a foundation for standardising the diagnosis for disorders of gut-brain interaction. Based on where they met up, they decided to call this the Rome Criteria. Skip to 2016, we have the newest version known as the Rome IV Criteria.

To meet the criteria, a person must have:

Recurrent abdominal pain, on average, at least 1 day per week in the last 3 months,
associated with at least two of the following:

1. Related to defecation (exacerbated or relieved)

2. Associated with a change in stool frequency

3. Associated with a change in stool form (appearance)

Symptoms must have started at least 6 months ago.

IBS is further sub-typed based on stool consistency (using the Bristol Stool Chart):

• IBS-C: Constipation-predominant

• IBS-D: Diarrhoea-predominant

• IBS-M: Mixed (alternating)

• IBS-U: Unclassified

Importantly, IBS is a clinical diagnosis; investigations are used to rule out red flags, not to confirm IBS.

What is visceral hypersensitivity?

Essentially this is when normal digestive sensations that others barely notice can feel painful or uncomfortable to you. Visceral hypersensitivity affects 60-90% of patients with IBS.

Imagine turning up the volume on a speaker so high that even whispers sound like shouts. That's what's happening with your gut's pain signalling system.

We know that reduced prefrontal cortex grey matter and heightened amygdala reactivity, correlate with pain amplification and emotional distress.

This is why neuro-modulators, drugs that act on both the central and peripheral nervous system, have been clinically found to improve abdominal pain in IBS

Disorder of the gut-brain axis

Re-capping from earlier, in IBS the enteric nervous system is essentially mis-firing signals to the brain. For example:

When you have IBS-D (diarrhoea type), your gut might release too much serotonin – a chemical messenger that speeds up digestion.

With IBS-C (constipation type), there's often too little serotonin, slowing everything down.

Your brain's stress response centre also plays a key role.

Chronic stress activates your body's alarm system, releasing hormones that can increase gut sensitivity, alter movement, and affect the protective barrier of your intestines.

Is IBS inflammatory? Is there an immune component?

Many people with IBS, especially those whose symptoms started after food poisoning or an infection (post-infectious IBS), have subtle inflammation in their gut lining.

This is not visible during standard tests but can be detected with specialised measurements in the form of inflammatory cytokines, intra-epithelial lymphocytosis and mast cell activation.

Mast cells are a type of immune cell which are often increased in IBS and tend to sit unusually close to nerve endings in your gut.

When these cells release their inflammatory chemicals, tryptase and protease, they directly trigger pain signals and can disrupt your gut's protective barrier.

Microbiome Imbalance (dysbiosis)

The trillions of microorganisms living in your gut (your microbiome) look different in people with IBS:

• Fewer beneficial bacteria like Bifidobacterium and Lactobacillus

• More potentially problematic bacteria

• Less overall diversity

These changes affect how your body processes food, produces helpful compounds like short-chain fatty acids, and maintains gut barrier integrity.

Risk Factors: Why Did I Get IBS?

Who Gets IBS?

• Gender: Women are 2-2.5 times more likely to develop IBS, partly due to hormones like oestrogen affecting gut sensitivity and muscle contractions.

• Age: Most cases begin between ages 20-40, though symptoms can start earlier or later.

• Family history: Having a close relative with IBS doubles your risk, suggesting both genetic and environmental factors are at play.

Life Experiences and Psychological Factors

• Mental health: Anxiety and depression are common companions to IBS, with each making the other more likely.

• Early life stress: Difficult childhood experiences, particularly trauma or abuse, significantly increase IBS risk by affecting how your stress response system develops.

Triggers and Environmental Factors

• Infections: 10-30% of IBS cases develop after food poisoning or gastroenteritis .

• Antibiotics: These can disrupt your gut microbiome, sometimes triggering IBS symptoms.

• Diet: Foods high in FODMAPs (fermentable carbohydrates), low fibre intake, or processed foods may worsen symptoms in susceptible individuals. I plan to deep-dive into this soon, in a future newsletter.

• Lifestyle: Sedentary behaviour, smoking, and in some cases, alcohol can influence IBS development or symptom severity.

What This Means for Your Treatment

Understanding these mechanisms helps explain why IBS treatment often requires a biosocial approach:

• Diet modifications address food triggers and support microbiome health

• Stress management techniques help calm the overactive brain-gut connection

• Medications target specific pathways to ease the enteric nervous system, like serotonin signalling, or mast cell activity

• Probiotics may help restore microbiome balance

• Physical activity improves gut motility and stress resilience

The future of IBS treatment looks promising, with new therapies targeting mast cells, microbiome restoration, and even ways to modify how genes express themselves in your gut.

To summarise…

IBS is not "just stress" or something you have imagined.

It is a real condition involving complex interactions between your nervous system, immune system, gut microbiome, and life experiences.

While we can't yet cure IBS, understanding these mechanisms can help you work with your healthcare provider to find the most effective treatments for your unique situation.

Remember, knowledge is power…especially when it comes to managing a condition as complex (and perhaps poorly understood) as IBS.

Did you enjoy this article?

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References

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2. Farzaei MH et al. The Role of Visceral Hypersensitivity in Irritable Bowel Syndrome: Pharmacological Targets and Novel Treatments. J Neurogastroenterol Motil. 2016 Oct 30;22(4):558-574.

3. https://www.scielo.br/j/rdor/a/fcjRkWvWWx9GQD7dR7Y43NP/

4. Chang, X., Zhang, H. & Chen, S. Neural circuits regulating visceral pain. Commun Biol 7, 457 (2024)

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8. Hussein H, Van Remoortel S, Boeckxstaens GE. Irritable bowel syndrome: When food is a pain in the gut. Immunol Rev. 2024 Sep;326(1):102-116

9. Kirkik D, Kalkanli Tas S. Unveiling the intricacies of irritable bowel syndrome. World J Gastroenterol. 2024 Nov 28;30(44):4763-4767.

10. Dothel G et al. New insights into irritable bowel syndrome pathophysiological mechanisms: contribution of epigenetics. J Gastroenterol. 2023 Jul;58(7):605-621

11. Almadi MK, Sabr MS, Kofi M, Alaboodi T, Al Sayari TA. Epidemiology and Risk Factors of Irritable Bowel Syndrome in the Saudi Population: A Systematic Review. Cureus. 2025 Mar 3;17(3):e79974.

General Disclaimer

Please note that the opinions expressed here are those of Dr Hussenbux and do not necessarily reflect the positions of Buckinghamhsire Healthcare NHS Trust. The advice is intended as general and should not be interpreted as personal clinical advice. If you have problems, please tell your healthcare professional, who will be able to help you.