IBS (Irritable Bowel Syndrome) Causes

Medically reviewed by:

Dr Sarah Marshall - Medical Officer

Updated: Aug 18, 2021

Next review: Aug 18, 2022

The exact cause of IBS is not fully understood, but according to the IBS network, it affects around 10%-20% of people in the UK, so it is relatively common.

If your digestive system works as it should, it moves food through it by squeezing the intestine’s muscles. If you have IBS, this doesn’t happen as it should, causing pain, cramping and discomfort – the severity will vary from person to person.Food can travel too slowly (causing constipation) or too quickly (causing diarrhoea) through your system.

Some suggestions on why this happens include:

Stress, anxiety or extreme emotions – these may play a part, as a lot of people report their IBS started after a stressful event or is triggered by these emotions.
Gastroenteritis – other people report that their IBS began following an infection in their gut, known as gastroenteritis.
Overactivity – it is possible that the messages your brain sends to your gut causes the nerves and muscles in your gut to behave unusually.
Food intolerance – a food intolerance may contribute to their IBS.
Oversensitivity – it has been suggested that people with IBS have a lower pain threshold than people without it, so they feel pain when their gut is expanded.

A lot of people with IBS find that something ‘triggers’ their symptoms. When you know what it is that causes your IBS to flare up, you can try to avoid it. Things that are thought to trigger the condition include:

The foods you eat

Certain food and drink can set off IBS, although the food and drinks will vary from one person to the next.

To identify what your triggers are, you can keep a food diary for two to four weeks to monitor what you are eating and when your symptoms flare up. However, there are certain foods and drinks that are known to be likely triggers.

Triggers for IBS with diarrhoea include:

Fibrous food, such as fruit and veg
Chocolate
Carbonated (fizzy) drinks
Alcohol
Caffeine
Fried or fatty food
Big meals
Dairy

Triggers for IBS with constipation include:

Processed snacks, like biscuits and crisps
Drinks that have caffeine in them
Bread and cereal with refined grains, like white bread
Lots of protein
Dairy

Once you know what food or drink sets off your IBS, you can try to avoid it to help prevent the symptoms occurring.

Psychological triggers

Psychological triggers may also play a role in IBS. As we mentioned briefly earlier, anxiety and stress can affect the messages your brain sends to your nerves and muscles in your gut and cause the body to trigger chemical changes, sending your digestive system into overdrive.
If you know that stress and anxiety trigger your IBS,you may try to avoid the situations that cause the problem, although we understand that is often easier said than done and can sometimes cause more problems.
Medication triggers
Some medications can trigger IBS symptoms, including antibiotics, certain antidepressants and medicines that are made with sorbitol, which can have a laxative effect.
Hormonal triggers
Women are more likely to suffer with IBS, and symptoms can be at their worst during your period.

Some people are more at risk of developing IBS than others. Some of the factors that may put you more at risk include:

Family history – if your parent or sibling has IBS, you are more likely to develop it.
Gender – women are more prone to IBS than men – it could have something to do with changing hormone levels during the menstrual cycle.
Age – IBS usually appears between the ages of 20 – 30, although it can affect people of all ages.
Medication – antidepressants and antibiotics have been shown to show links to IBS.
Food poisoning – IBS may develop after you have suffered a bout of food poisoning.
Meal times – if you eat at irregular times, you may be more likely to develop the condition.

Dr Colin Tidy. Patient Info, Irritable Bowel Syndrome, 02/07/2017.
patient.info/health/irritable-bowel-syndrome-leaflet#nav-2
Dr Minesh Khatri, Web MD, IBS Triggers and How to Avoid Them, 25/03/2018.
webmd.com/ibs/ibs-triggers-prevention-strategies#1
NHS Inform, Irritable bowel syndrome (IBS), 01/05/2018.
nhsinform.scot/illnesses-and-conditions/stomach-liver-and-gastrointestinal-tract/irritable-bowel-syndrome-ibs#causes
IBS Network, IWhat is the cause of IBS, 2018.
theibsnetwork.org/have-i-got-ibs/what-is-the-cause-of-ibs/

IBS (Irritable Bowel Syndrome) Causes

Dr Sarah Marshall - Medical Officer

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