Irritable bowel syndrome with mixed bowel habits (IBS-M) refers to a type of irritable bowel syndrome (IBS) where someone experiences episodes of both diarrhea and constipation. This differs from other types of IBS, where a person typically experiences one episode.

IBS is a chronic condition that affects the digestive system. It can cause stomach pain and changes in bowel movements. Within the spectrum of IBS, there are several subtypes, one of which is IBS-M, which is also known as mixed-type IBS.

This article explores IBS-M in more detail, including causes, treatment, and symptoms.

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IBS is one of the most common gastrointestinal conditions. Symptoms of IBS often include stomach pain or discomfort, in addition to alterations in bowel movements. Many people with IBS will have days of typical bowel movements and atypical movements on other days.

Broadly, there are three subsets of IBS — these are:

  • IBS with diarrhea (IBS-D)
  • IBS with constipation (IBS-C)
  • IBS-M

As the name suggests, IBS-M has an alternating pattern of symptoms. Individuals with IBS-M may experience episodes of constipation and then periods of diarrhea, or they might encounter both simultaneously. The variability and unpredictability of symptoms can make IBS-M particularly challenging to manage.

The exact cause of IBS and IBS-M is unknown. Experts believe that several issues may contribute to a person developing the condition.

IBS-M is a type of functional gastrointestinal disorder. These conditions revolve around disruptions in how the brain and gut collaborate. Researchers speculate that these disruptions can influence bodily functions and generate IBS-M symptoms. For example, food might either pass through the digestive tract too slowly or too swiftly, leading to alterations in bowel movements.

Factors such as stress, dietary habits, hormonal changes, altered gut motility, and imbalances in gut bacteria also contribute to the occurrence of IBS-M symptoms. For some individuals, certain foods or food groups may trigger symptoms, aggravating the condition.

A 2023 study also suggests that genes may play a part in making some people more susceptible to developing a subset of IBS.

The distinguishing feature of IBS-M from other IBS subsets is that a person will experience both constipation and diarrhea. The National Institute of Diabetes and Digestive and Kidney Diseases provides guidance on the criteria to meet a diagnosis of IBS-M. It states that on the days that someone is experiencing at least one atypical bowel movement, more than 25% of the stools are hard or lumpy (constipation) and more than 25% are loose or watery (diarrhea).

Apart from constipation and diarrhea, a person living with IBS-M may also experience the following symptoms:

  • stomach ache or pain
  • stomach discomfort
  • nausea
  • bloating
  • gas

A 2019 article suggests that the severity and frequency of these symptoms can vary among affected individuals.

Diagnosing IBS-M involves a comprehensive evaluation by a healthcare professional.

Initially, a doctor will review a person’s symptoms to seek a specific pattern that indicates IBS. During this review, a doctor may make a diagnosis if a person is experiencing stomach pain in addition to two or more of the following symptoms:

  • pain when passing a bowel movement
  • changes in stool appearance
  • change in the frequency of bowel movement

During this assessment, a doctor will also consider the length of time someone has been experiencing these symptoms. They will also factor in whether there is a family history of gastrointestinal conditions, lifestyle factors, and dietary habits.

There is no specific test for IBS, but a doctor may use tests to rule out other potential health problems. These can include:

  • Breath tests: These check for bacterial overgrowth in the small intestine or problems digesting carbohydrates.
  • Blood tests: These help rule out other conditions such as an infection or anemia.
  • Stool tests: These check for blood or bacteria, which may indicate infection or other diseases.
  • A colonoscopy: This test helps rule out conditions, such as inflammatory bowel disease.

Generally, managing IBS-M involves implementing various lifestyle modifications to minimize triggers and improve overall gut health.

Research suggests that adopting a low FODMAP diet may relieve symptoms of IBS in some individuals. This diet involves restricting certain types of carbohydrates that the small intestine may have difficulty absorbing.

The same research also suggests the following lifestyle recommendations for people living with IBS, including IBS-M:

  • adopting stress management techniques
  • staying active
  • sleeping and resting
  • avoiding spicy and high fat foods
  • avoiding alcohol
  • avoiding overeating, especially at night

Although there are no medications to treat IBS-M directly, there are medications to help alleviate specific symptoms.

For individuals experiencing abdominal pain and cramping, healthcare providers may recommend antispasmodics to relax the muscles in the digestive tract. Other medicines, such as antidepressants, can also help alleviate abdominal pain symptoms of IBS-M.

As the symptoms of IBS-M alternate between diarrhea and constipation, a person should be cautious about taking any over-the-counter medications that ease these symptoms.

As well as medication and lifestyle changes, a person living with IBS-M may consider complementary and alternative medicines to help ease symptoms.

Probiotics contain bacteria similar to the beneficial bacteria that naturally occur in a person’s gut. Taking these may offer some relief to IBS-M symptoms.

Research shows promising results that natural remedies, such as peppermint oil, can ease abdominal pain in those experiencing IBS-M.

Additionally, older research suggests that acupuncture may provide relief to IBS symptoms.

If a person is considering alternative approaches to managing their symptoms, they need to consult with a doctor before trying them. This is because they might be unsuitable and could interact with prescribed medications.

Irritable bowel syndrome with mixed bowel habits (IBS-M) is a subset of IBS in which a person experiences alternating episodes of diarrhea and constipation. A person may also experience other symptoms, such as abdominal pain and stomach discomfort. While its exact causes remain unknown, a combination of factors, including genetics, may contribute to its development.

Effective management of IBS-M often involves a multidisciplinary approach, including lifestyle changes and, in some cases, medication to alleviate symptoms.