What Are The Causes Of IBS?

In the 1950s and 1960s, irritable bowel syndrome (IBS) was largely believed to be connected to psychiatric illness. Starting in the 1960s, the cause of IBS shifted to abnormalities in the spontaneous movements of the gastrointestinal tract. In the 1970s and 1980s, a new concept suggested that a hypersensitive intestine can be affected by different triggers, which may lead to gastrointestinal symptoms. Since the 1990s, research led to the idea that there may be an abnormal brain response to changes in the gut.¹ Despite all the advances in research, the cause of IBS is still not fully understood.^1,2 IBS is likely due to three key factors, which are environmental factors, psychosocial factors, and gut physiology.^2,3 These three factors may work independently or in combination. Below are some examples of these factors.³

Environmental factors:³

• Genetics
• Food
• Gastrointestinal Infections or enteritis

Gut physiology:³

• Inflammation
• Altered intestinal environment
• Abnormal gut/brain response

Psychosocial factors:³

• Stress
• Anxiety

How do environmental factors, gut physiology, and psychosocial factors cause or trigger IBS?

A healthy intestine functions as a barrier between the gut, which may include food and ingested bacteria, and the rest of the body. An increasingly sensitive intestine may develop as a result of different triggers, which may lead to inflammation and pain sensations. Some possible triggers may be stress, anxiety, and food. The involvement of stress and food in IBS is still not completely understood, but it is generally believed to be a trigger and not a cause of IBS. Stress may increase the likelihood that there will be changes to the body’s immune system and the proper functioning of the intestines, leading to altered or painful bowel movements. Similarly, food allergies or hypersensitivities may irritate the intestines and lead to abdominal pain.² Although there are many possible food allergies and hypersensitivities, there is likely a proportion of people with IBS who have sensitivity to certain sugars or carbohydrates (eg, gluten) or is lactose intolerant.^2,3

Infectious gastroenteritis may trigger inflammation, which is referred to as post-infectious IBS. Foreign bacteria in the gut may disrupt the normal environment of the intestine and lead to intestinal inflammation. Up to one-third of IBS cases follow acute gastroenteritis. Symptoms may persist when coupled with stress and anxiety.³

Abnormal brain responses to bowel signals and rectal stimulation, as well as gut-based factors, including inflammation, infection, and the altered movement of food through the gut may contribute to the development of IBS.³

Some evidence exists to suggest that there is a genetic basis for IBS. The genetic connection to IBS may be a predisposition to hypersensitivity, triggers to inflammation, pain response, and other environmental influences.³