The causes of Irritable Bowel Syndrome are multifactorial and not yet fully understood.
Unlike many gut disorders that come from clear issues like infection or inflammation, Irritable Bowel Syndrome (IBS) works differently. It is a functional disorder. This means the gut looks normal but doesn’t work as it should. Instead of one cause, many things combine to affect how the gut moves, feels, and talks to the brain.
Researchers have found a strong link between the brain and gut. This is known as the gut-brain axis. This link plays a big role in the start and continuation of Irritable Bowel Syndrome. Many body and lifestyle factors can change how this connection works. That can lead to pain, irregular bowel habits, and bloating.
Let’s explore the most common causes of Irritable Bowel Syndrome and how they come together to create this long-lasting condition.
Abnormal Gut Motility in Irritable Bowel Syndrome
The muscles in the gut squeeze in waves to move food along. This is called peristalsis. In people with IBS, these muscle waves don’t always work right.
In IBS-D (diarrhoea type), the waves move too fast. This causes cramps, urgency, and watery stools.
In IBS-C (constipation type), the waves move too slowly. This leads to hard stools and bloating.
In IBS-M (mixed type), the motion switches between fast and slow without warning.
Several things can cause these changes. Nerve issues, hormone shifts, and brain chemicals like serotonin can all affect how the gut moves.
Visceral Hypersensitivity
Many people with IBS feel pain from things that don’t bother others. This is called visceral hypersensitivity. Even normal gas or stool movement can feel painful or urgent.
Why does this happen? There are a few reasons:
- Changes in how the brain handles pain
- Anxiety or stress that makes the gut feel extra sensitive
- Old infections or injury in the gut that make it more reactive
This pain is very real. Brain scans show that people with Irritable Bowel Syndrome have more brain activity when the gut is triggered.
Gut Microbiota Changes and IBS
The gut is full of tiny life forms called microbes. These include bacteria, viruses, and fungi. Together, they make up the gut microbiome. These microbes help break down food, keep your immune system strong, and even affect your mood.
In many people with IBS, this microbiome gets out of balance — a problem called dysbiosis.
Studies show:
- IBS patients often have less variety in gut bacteria
- Helpful bacteria like Lactobacillus may be missing
- Harmful bacteria may grow too much and cause gas or bloating
Things like antibiotics, stress, poor diet, or infections can upset the balance. To fix this, some people try probiotics, diet changes, or even stool transplants.
Post-Infectious Irritable Bowel Syndrome
Some people get IBS after a bad stomach infection. Bacteria like Salmonella, Campylobacter, or E. coli can cause long-term effects. This type is called post-infectious IBS.
In these cases, the infection can lead to:
- Swelling in the gut
- Long-term problems with gut movement
- Changes in gut bacteria
- Damage to gut nerves, making it extra sensitive
The longer and harsher the infection, the more likely IBS will follow. People with certain genes or mental health issues may also be more at risk. This kind of Irritable Bowel Syndrome can last months or even years.
The Role of Stress and Emotions in Irritable Bowel Syndrome
Emotions don’t cause IBS, but they make it worse. Stress, anxiety, and depression can flare up symptoms and make them harder to manage.
The brain and gut talk to each other through nerves and hormones. When you’re stressed, this communication gets messed up.
Stress can:
- Make the gut leakier
- Trigger swelling
- Mess with how the gut moves
People with anxiety or depression often have Irritable Bowel Syndrome. Childhood trauma also increases the risk later in life. Thankfully, treatments like talk therapy, hypnosis, or mindfulness can help manage these symptoms and ease gut pain.
Hormones and Irritable Bowel Syndrome
Women get IBS more than men, especially during their childbearing years. Hormones like oestrogen and progesterone seem to play a big role.
Many women notice worse symptoms during their period. These hormone changes can affect:
- How the gut moves
- How easily things pass through
- How much pain the gut feels
IBS often improves after menopause. But for some, pregnancy or birth control pills can make things worse.
Food Triggers and Irritable Bowel Syndrome
IBS is not a food allergy, but some foods make symptoms worse. The biggest problem foods include:
- FODMAPs – sugars that are hard to digest and create gas
- Lactose from dairy
- Fructose in fruits and syrups
- Gluten in wheat and bread
Not everyone reacts the same. But if your body is already sensitive, these foods can add fuel to the fire. Many people find relief with a low-FODMAP diet, which helps calm the gut and reduce symptoms of Irritable Bowel Syndrome.
Genetic and Family Links to Irritable Bowel Syndrome
IBS can run in families. If someone close to you has it, your chances go up. But no single gene causes it.
Family links may come from:
- Inherited traits like sensitive guts
- Shared ways of handling stress
- Passed-down gut bacteria
Even twins show some genetic influence. Still, it’s just one part of a much bigger picture.
Immune System and Irritable Bowel Syndrome
Some people with IBS, especially those with diarrhoea, have slight immune problems. Their gut lining may be inflamed or too open, often called “leaky gut.”
This can lead to:
- Irritated intestines
- Gut lining that lets things pass too easily
- Pain from things that shouldn’t hurt
This immune trouble may be leftover from infections or long-term stress. It also connects closely with changes in gut bacteria.
Conclusion
The causes of Irritable Bowel Syndrome are wide-ranging. They include gut movement issues, pain sensitivity, microbiome shifts, weak immunity, hormone changes, food triggers, and mental health struggles. Each person may have a different mix of these factors.
By understanding these root causes, doctors can find better ways to help people. Treating IBS is not just about easing symptoms. It’s also about addressing the deeper reasons behind them. As research grows, the future holds more targeted and helpful treatments for Irritable Bowel Syndrome.
