Causes of Irritable Bowel Syndrome (IBS)

It’s not easy to figure out what causes IBS, although many sufferers will eventually identify triggers for their condition.

You might be able to date your symptoms back to a particular event, such as a bout of food poisoning, an episode of high stress [link to IBS and stress page] or a surgical procedure.

Nothing has yet been scientifically proven to directly cause IBS however it appears to have both a psychological and physiological element. Depending on the individual, either or indeed both of these elements can be involved.

What we do know is that it’s probably linked to an increase in the gut’s sensitivity. The nerves and muscles of the gut then may overreact to a variety of stimuli. There is also evidence that the type and balance of bacteria in the gut play a role in IBS.

Normally, the muscles in the intestines squeeze and relax to move food gradually through the digestive system. IBS is caused when this finely tuned rhythm is disturbed and food moves too quickly (leading to symptoms such as diarrhoea [link to symptoms of diarrhoea page]) or too slowly (leading to symptoms such as constipation.

But why does this increase in sensitivity happen in the first place? The root causes of IBS are likely to be linked in some way to the brain and nervous system.

It’s been suggested that the muscles of the intestines are disrupted because they don’t receive the right signals from the brain, telling them how to behave. Issues such as stress, depression and changes in hormone levels could interfere with this signalling process.

Nerve signals that usually tell your brain you’ve eaten enough may instead make you feel like you’re bloated and constipated.

This brain-gut connection goes a long way to explaining the causes of IBS and could explain why many people find that stress and anxiety can trigger IBS.

Disturbances in the bacteria that populate the gut may play a role in some sufferers of IBS specifically;

  • An imbalance in the gut bacteria brought about by antibiotics has been known to trigger IBS in some individuals.
  • Other people may suddenly develop IBS following an episode of gastroenteritis, a condition known as post-infectious IBS (PI-IBS).
  • Low level inflammation may be present in the bowel wall of some IBS sufferers which may be linked to abnormal interaction with the bacteria in the gut.
  • Small intestinal bacterial overgrowth (SIBO) may be associated with IBS
  • Recent research has shown that the balance of bacteria in the gut may also influence anxiety.




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