Irritable Bowel Syndrome (IBS)

May 2025 | Brian Chicoine, MD - Medical Director, Adult Down Syndrome Center

Key Points

Irritable bowel syndrome (IBS) is one of a group of disorders related to the interaction between the gut and the brain (nervous system).
IBS is probably more common in people with Down syndrome.
IBS can cause many symptoms such as constipation, diarrhea, abdominal pain, and others. It also may contribute to a feeling of stress, which can exacerbate IBS.
There are criteria (Rome IV) for diagnosing IBS. There are no specific tests to diagnose IBS; however, it is important to test for other possible causes of the symptoms.
There are a variety of treatments including dietary change, stress reduction, and medications.

What is irritable bowel syndrome?

Irritable bowel syndrome (IBS) is a health issue in the intestines (bowels). It is in a group of disorders related to the interaction between the gut and the brain (nervous system). These disorders were formerly known as “functional” because they do not have a clear structural or biochemical cause. However, additional study has found that these conditions are related to:

Altered or different processing by the brain of signals from the gut
Increased sensitivity in the gastrointestinal (GI) tract to normal signals from the nervous system
Atypical motility (the stretching and contracting of the GI tract that moves food and waste material through the GI tract)
"Leaky gut" - reduced function of the mucosa (moist inner lining of the GI tract) and the immune system

Additional factors that seem to increase the risk of developing IBS include:

History of a severe infection
Stress in early life
Changes in gut microbes (bacteria, fungi, and viruses)

IBS is a common problem. According to the American Gastroenterological Association, it is estimated to affect more than 35 million people in the United States.

Why is IBS important in Down syndrome?

It is not clear how common IBS is in adults with Down syndrome, but it does appear to be more common. One study found that 14.9% of children with Down syndrome in the study had IBS.

IBS may be more common in people with Down syndrome because:

The motility of the gut is often altered in people with Down syndrome
One response to stress for many people with Down syndrome seems to be a change in their GI system

More information on the function of the GI tract in people with Down syndrome is available in the Resources section at the end of this article.

Symptoms and signs

Symptoms of IBS can include:

Abdominal pain
Cramping
Gas
Bloating
Changes in the frequency of bowel movements (e.g., diarrhea or constipation)
Changes in the appearance or consistency of bowel movements
Feeling like your bowels have not emptied fully after having a bowel movement

People with IBS may not have symptoms all the time. They may have “flare ups,” or periods of time when symptoms are worse than at other times. IBS does not cause bleeding of the intestines, cancer, or long-term harm to the bowels.

When the intestines of someone with IBS are examined, there is no abnormality seen. Even though it cannot be seen, IBS can cause significant pain and affect a person physically, emotionally, and socially. Additionally, physical, emotional, and/or social stress seem to increase symptoms of IBS for some people.

There are three types of IBS:

IBS with constipation (IBS-C)
IBS with diarrhea (IBS-D)
IBS with mixed symptoms (IBS-M) – can have symptoms of both IBS-C and IBS-D)

Diagnosis

The Rome IV Criteria have been developed to make the diagnosis of IBS. The criteria require the following symptoms for diagnosis:

Recurrent abdominal pain on average at least 1 day per week in the last 3 months, associated with 2 or more of the following:

Related to defecation (having a bowel movement)
Associated with a change in frequency of stool
Associated with a change in form (appearance) of stool

The diagnosis of IBS is usually not given unless testing has ruled out other causes of a person’s symptoms. However, there are no tests that can be done to specifically diagnose IBS.

An evaluation with a health care professional starts with a good history. The patient and family will be asked to provide details of the symptoms, any testing that has already been done, and other health conditions the patient has. Questions may include:

What are the triggers? Are there particular times (or places) where the symptoms occur?
Are there other symptoms (such as bleeding) that may be caused by another condition?
Is there a family history of IBS?
Has the person been diagnosed with any health conditions that may be contributing?
Has the person been assessed for other health conditions, particularly those that are more common in people with Down syndrome? For example, people with Down syndrome are more likely to have:
- Hirschsprung’s disease
- Celiac disease
- Inflammatory bowel disease (Crohn’s disease and ulcerative colitis)

The health care professional will then do a physical exam. Based on the history and exam, they may recommend one or more tests.

Blood testing to assess for other causes of the symptoms. Blood work may include:
- Complete blood count (CBC) to assess for anemia
- Chemistry panel (CMP or BMP) to assess for liver or other problems
- Tissue transglutaminase IgA and total IgA to assess for celiac disease
Other tests depending on the symptoms
- Stool testing for infections
- Imaging such as abdominal x-rays; CT scan of the abdomen and pelvis; ultrasound of the gall bladder, liver, and pancreas; and others
- Breath test or other test to assess for lactose intolerance (intolerance of the sugar in dairy)
- Upper endoscopy (EGD) and/or colonoscopy

Treatment

In our experience in working with people with Down syndrome, we have recommended a variety of treatments. Both the condition and the treatment tend to be unique for each person, so careful assessment of the individual’s symptoms, triggers, etc. is needed to determine the treatment approach. Ongoing reassessment is important for determining what measures seem to be helpful and should be continued, what measures do not seem to be helpful and should be eliminated, and what new approaches should be considered if the present ones are not working well.

Diet and nutrition

The dietary needs of people with IBS vary, so what works for one person may not work for another. Doing a food journal before changing the diet can help determine if there are certain foods that contribute to the symptoms. A food journal is a daily log in which a person records what food was eaten and what symptoms were experienced. After several days or weeks, the log can be reviewed to see if there is a possible association between certain foods and symptoms that suggests that certain foods should be avoided or eliminated. Care is advised to avoid attributing symptoms incorrectly because foods may unnecessarily be avoided which can contribute to food aversion.

Some diet management strategies that may be beneficial include:

Limiting dairy products and high-fat foods
Including plenty of fiber in the diet
Limiting or eliminating highly processed foods
Drinking plenty of fluids (particularly when constipation is a symptom)
Promoting a healthy balance of bacteria in the gut (for example, by eating more fiber, fruits, vegetables, and yogurt)
Limiting coffee and other sources of caffeine
Eating smaller portions (some find it helpful to eat smaller portions more frequently rather than following a typical 3-meal schedule)
Low-FODMAP diet (limits certain kinds of carbohydrates that are difficult to digest)

Medical management

There are several medications that may help with symptoms including:

For IBS-D, medications that slow or stop diarrhea such as loperamide (Imodium) and others
For IBS-C, medications that treat constipation such as fiber supplements, stool softeners, laxatives, and others.
Probiotics
If anxiety or depression are contributing to symptoms, antidepressants and anti-anxiety medications may be beneficial.
Anti-spasm medications