The Different Sub-Types of IBS

Have you found that your IBS is very different from your friend's IBS? Or that the stories you read about on the Internet don't always sound like your life? That is because IBS can show up in so many different ways — causing dramatically different symptoms from one person to another.

What all types of IBS have in common is the experience of chronic bowel movement problems. Official diagnostic guidelines also require the symptom of chronic abdominal pain, but in the real world, doctors tend to give the diagnosis of IBS to anyone who is experiencing problems associated with their intestines that cannot be attributed to a visible disease process, such as one of the inflammatory bowel diseases.

Note: If you are experiencing chronic pain or bowel movement problems, it is essential that you see a doctor for an accurate diagnosis. Many of the symptoms that you will read about in this article are also associated with other, more serious health disorders.

woman talking to doctor about stomach pain
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Official IBS Sub-Types

Due to the fact that IBS has such variable symptoms, medical professionals classify IBS patients according to a few different sub-types. Although all patients must meet Rome III criteria for diagnosis, their sub-type will be determined by their predominant bowel movement problem.

Diarrhea-Predominant IBS

People who have diarrhea-predominant (IBS-D) experience the following symptoms on a regular basis:

The Rome III criteria for IBS-D state that symptoms must be experienced on at least three days per month.

Constipation-Predominant IBS

People who have constipation-predominant IBS (IBS-C) have the following symptoms to deal with on a regular basis:

As with IBS-D, the Rome criteria require that the above symptoms must be present at least three days a month for the past three months for a diagnosis of IBS-C.

Alternating Type IBS

People who have alternating type IBS (IBS-A) find themselves without any consistent bowel habits. This type of IBS involves dealing with both constipation and diarrhea episodes. The Rome criteria state that each stool change (e.g. hard and lumpy or loose and mushy) is experienced for at least 25% of all bowel movements. People with IBS-A may experience these changes all within the same month, week, or even day!

Symptoms of All Types

Regardless of subtype, most people who have IBS experience the following symptoms on a regular basis:

Prevalence of Each Sub-Type

How many people have each sub-type? Studies regarding prevalence rates of the various sub-types have not come to any firm conclusions. Some studies show equal rates for all three sub-types, while others show a higher prevalence for one over the other two. These contrasting findings may be due to different manifestations of the disorder in different geographic areas, or the differences are a reflection of who actually seeks medical attention for their symptoms, or may simply reflect the difficulties inherent in measuring IBS symptoms in general.

Can People Switch From One Sub-Type to Another?

Yes, they can. This is a different experience from IBS-A, which involves switching back and forth from the experience of diarrhea and constipation on a regular basis. Because IBS is a chronic, persistent health problem, it is not uncommon for people to experience a switch from one sub-type to another at various points in their life.

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By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.