IBS Causes and Triggers Overview

Doctors do not know the exact reasons why a person develops irritable bowel syndrome (IBS). Common theories suggest it is a combination of factors and that every person has a different experience. What triggers IBS symptoms to worsen can also vary.

Theories on IBS causes

Doctors have different ideas about the potential causes and triggers of IBS.

Gut motility issues

Motility is a word used to describe the contraction of muscles in the gut that move, mix, and allow for the absorption of food. Some people may have an exaggerated or abnormal response to gut-related hormones. This can change the way the muscles in the intestine contract. The time it takes for food to move through the colon may increase or decrease depending on the type of symptoms experienced (constipation versus diarrhea).1-3

Increased sensitivity of the gut

There may be issues with the way the brain and gut communicate, leading to an increased sensitivity to pain signals. This is also called visceral hypersensitivity.1-3


A person with IBS may have an abnormal balance of immune system cells along the gastrointestinal tract (GI). An increase in immune cells can produce inflammation and signals that lead to changes in gut function. This can cause IBS-related symptoms such as pain or diarrhea.1-3


Infections caused by viruses, bacteria, or other germs can cause changes in the gut that lead to IBS. Other factors that can throw the gut off balance and lead to IBS symptoms include:1-3

  • Difficulty absorbing nutrients
  • Increases in hormone-producing or immune system cells
  • Antibiotics used to treat infections

Food sensitivities

Food allergies or intolerances, as well as issues absorbing nutrients, can lead to IBS-related symptoms. However, it is unclear if these lead to IBS itself or if the condition shares symptoms with other, separate disorders like celiac disease.1-3


People with IBS are more likely to have family members with IBS. While scientists are still studying the genes linked to IBS, this suggests that certain genes may increase a person’s risk of developing IBS.1-3

Psychosocial distress

The brain and gut are closely connected. When the brain is experiencing distress, the gut can as well. Distress can be related to:

This is why stress relief, mental health support, and antidepressants are part of the IBS treatment plan.1-3

This is not a full list of potential causes of IBS. For more information on your situation, talk with your doctor.

Potential IBS triggers

Similar to IBS causes, each person's experience with triggers will differ. However, there are some common themes that many people report.4-6

Specific foods

The foods that trigger symptoms in one person may not affect others. However, common trigger foods include:4-6

  • Those with high amounts of insoluble fiber, such as crackers, popcorn, quinoa, nuts, seeds, and whole wheat pasta
  • Dairy
  • Fatty foods
  • Beans
  • Caffeine
  • Alcohol
  • Processed foods
  • Vegetables that produce gas, such as broccoli, cauliflower, kale, and cabbage
  • Greens such as chives, leeks, and shallots


The intestines and brain are connected, so when your mind is stressed, your gut may be too. In times of high stress, anxiety, or other disruption of your environment, it is not uncommon for IBS symptoms to worsen.4-6


Some drugs can impact IBS symptoms. Examples include antibiotics and antidepressants, which may play a role in the management of IBS or other medical conditions.

Your doctor can help you find a balance between the drugs you need and their effects on your IBS symptoms.4-6


IBS is more common in women than men. Many women report a worsening of symptoms around their menstrual cycle. While the exact relationship is not well understood, hormones may play a role in IBS and its severity.4-6

Keeping a diary of symptoms and triggers can be helpful in finding out what specific things make your IBS symptoms worse. Tracking how you navigate or reduce these triggers can also make a difference in preventing and handling symptoms in the future. You know your body best and can make a roadmap for yourself on how to best support it.

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Written by: Casey Hribar | Last reviewed: September 2021