Irritable Bowel Syndrome (IBS): Symptoms, Causes, and Treatment

Irritable bowel syndrome (IBS) is a functional disorder. This means you have real symptoms, but there are no physical changes or significant inflammation in your bowels (gut). The bowels may work differently in people with IBS, but the inside of the intestines is often normal. 

It’s not entirely clear what causes IBS. But it may have to do with how the intestines move.

IBS is a very common condition, but many people don’t know they have it. In the U.S., 15% of adults have symptoms of IBS. Only half of these people have an actual diagnosis of IBS.

What causes irritable bowel syndrome (IBS)?

Experts don’t know the exact cause of IBS. But there are some theories about why people may develop symptoms of IBS. These include:

• The brain-gut connection: There’s evidence of two-way communication between your brain and your gut. In people with IBS, signals from the brain — like stress — can have a big effect on how the gut works. At the same time, signals from the gut can also trigger changes in mood and how the brain functions. 

• The gut microbiome: Normally, your gut has a balance between healthy and harmful bacteria. When the balance of bacteria in your gut is off, it can lead to IBS symptoms. This can happen after an infection like food poisoning.

• Stress: Stressful or traumatic events may play a role in the development of IBS. These experiences could lead to chemical changes in your brain. This may affect how your gut moves and how you feel pain.

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Risk factors for IBS

Experts don’t know exactly what causes IBS, but they have identified who is more likely to get it. Risk factors for IBS include:

• Female sex

• Having anxiety or depression

• Eating a lot of ultra-processed or fatty food

• Having a bacterial infection in your gut, like Clostridioides difficile (C. difficile) or Escherichia coli (E.coli)

• Drinking alcohol

• Having food allergies or food sensitivities

• Going through stressful or difficult childhood events

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IBS symptoms

Most people with IBS have abdominal pain and changes in their bowel movements, like diarrhea, constipation, or both.

If you have IBS, you may also have other symptoms, like: 

• Bloating

• Gas

• Nausea

• Mucus in your stool

• Stomach cramps

• Feeling of fullness after eating

Every person with IBS experiences their symptoms in a different way. Your symptoms might not be the same as someone else’s. And your symptoms might be different with each IBS flare. The severity of the symptoms may also vary from person to person and with each IBS flare.

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Quiz: Do I Have IBS?

How is IBS diagnosed?

To diagnose IBS, a healthcare professional will start by asking you questions about your symptoms and medical history. They’ll also do a physical exam to rule out physical changes.

There isn’t one single test to diagnose IBS. But your healthcare professional might order other tests to make sure you don’t have other medical conditions — like inflammatory bowel disease (IBD), food intolerance, or colon cancer. 

You may need tests like: 

• Stool studies

• Hydrogen breath test

• Labs (like checking iron levels, a complete blood count, or food allergy testing)

• Colonoscopy

Types of IBS

There are several different types of IBS. Your treatment plan will depend on which subtype of IBS you have. After you’re diagnosed, your healthcare team may ask you to complete expert-designed questionnaires to help figure out your IBS subtype. 

The subtypes of IBS include:

• IBS-C (constipation): People with this subtype have a lot of constipation. 

• IBS-D (diarrhea): People with this subtype have a lot of diarrhea or loose stools.

• IBS-M (mixed): People with this subtype can have a mix of hard stools and loose, watery stools.

• IBS-U (unclassified): People with this subtype don’t have a consistent pattern to their stool changes. 

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Treatments for IBS

There are many different types of IBS treatments. Treatments may include changes in your diet and lifestyle as well as medications. 

Treatment plans aim to improve symptoms and are based on your IBS subtype. Since IBS symptoms can be different for each person, treatments will be different too.

Diet

Different foods can trigger IBS flares. You can reduce flares and improve your symptoms by avoiding triggers. Here are some dietary changes that may help:

• Eat more soluble fiber

• Avoid foods with gluten

• Eat more low-FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) foods like nuts, strawberries, spinach, and eggs

• Eat fewer high-FODMAP foods like dairy, beans, apples, and onions

• Avoid common food triggers like spicy or fatty foods

• Avoid common beverage triggers like alcohol, fizzy drinks, and caffeinated drinks

Lifestyle

In addition to changes in your diet, other lifestyle changes can help to decrease IBS symptoms. Here are a few tips you can try:

• Get more exercise: Engaging in moderate aerobic activity like walking or cycling may improve IBS symptoms. 

• Stop smoking: Smoking can make IBS symptoms worse. 

• Get more sleep: Poor sleep habits may increase your IBS symptoms. Try to get 7 to 9 hours of sleep each night.

Stress management

There’s a strong association between stress and IBS. High levels of stress can make your IBS symptoms worse. And IBS symptoms can lead to more stress and anxiety. Fortunately, there are ways to manage stress, including:

• Talking with a therapist

• Trying cognitive behavioral therapy (CBT)

• Using hypnotherapy techniques

• Practicing mindfulness techniques for stress reduction

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Medications for IBS

The medications used to treat IBS will depend on your symptoms and the subtype of IBS you have.

IBS-C

If you have IBS-C, constipation is a common problem. Over-the-counter (OTC) treatments that help soften your stool can provide some benefit. 

Prescription medications for IBS-C include:

• Trulance (plecanatide)

• Amitiza (lubiprostone)

• Linzess (linaclotide)

IBS-D

With IBS-D, you tend to have loose stools more often. Treatment usually focuses on calming gut irritation and reducing diarrhea. OTC antidiarrheal medications may reduce your number of loose stools.

Common prescription medications for IBS-D include:

• Xifaxan (rifaximin)

• Alosetron (Lotronex)

• Viberzi (eluxadoline)

IBS-M

People with IBS-M have mixed symptoms. The symptoms tend to alternate between diarrhea and constipation. This can sometimes make it hard to find the right medication. In many cases, dietary and lifestyle changes may be the most helpful.

Some medications help relieve the symptoms of IBS — no matter the subtype. These include:

• Tricyclic antidepressants (TCAs) like amitriptyline, nortriptyline, and desipramine can decrease IBS symptoms by changing your perception of pain and improving your mood.

• Antispasmodic medications like dicyclomine and hyoscyamine relax the muscles in your gut and improve movement. This may help with abdominal pain, cramping, and some of the stool changes with IBS. 

• Probiotics help balance the bacteria that are normally in your bowels. This can decrease irritation in your bowels caused by an overgrowth of unhealthy bacteria.

There are many treatment options for the symptoms of IBS. Your healthcare professional will work with you to figure out the best treatment plan based on your medical history and symptoms. 

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Preventing IBS flares

During an IBS flare, your symptoms like abdominal pain, bloating, constipation, or diarrhea get worse and harder to manage. Treatments like diet changes, lifestyle changes, stress management, and medications can all help lower the frequency or intensity of IBS flares. 

The best way to prevent IBS flares is to pay close attention to what triggers your symptoms. Keeping a journal can help you track patterns. Ask yourself: 

• Are there foods that seem to be triggering an IBS flare? If so, avoid them.

• Does stress seem like a common trigger? Think of ways to reduce stress. This can be anything from relaxation techniques to lowering your workload. 

• Am I sleeping well? If it’s hard to get quality sleep, work on sleep hygiene techniques.

• Is it time to start taking medication? If you’re still having IBS flares even after avoiding triggers, talk to a healthcare professional you trust to see if a medication would be right for you.