Causes and Risk Factors of Irritable Bowel Syndrome

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The exact cause of irritable bowel syndrome (IBS) is not completely understood. Sometimes it develops after a severe bout of infectious diarrhea or trauma, but in many cases, there is no specific incident. Researchers suggest causes may be some interplay of gut motility problems, visceral hypersensitivity, inflammation, or dysfunction of interactions between the brain and gut. Genetics, prior adverse life experiences, and some mental health conditions may predispose someone to IBS. Other factors the may cause or exacerbate IBS symptoms include stress, menstrual cycle hormones, smoking, and diet.

Common Causes

Overall, researchers are pursuing several areas in which there may be a difference between the bodies of people who have IBS and those who do not have the condition. These include motility, visceral hypersensitivity, inflammation, and gut bacteria.

Motility

Motility refers to the movement of the smooth muscle of the digestive tract. Although research has not shown consistent results, there is some evidence that the speed of this movement is altered in both the colon and the small intestines of individuals with IBS. Contractions that are faster than usual are seen in some individuals who suffer from diarrhea-predominant IBS (IBS-D), whereas the muscle movements are too slow in some individuals who suffer from constipation-predominant IBS (IBS-C).

Visceral Hypersensitivity

Visceral hypersensitivity is a heightened sense of pain in the internal organs of the body. Studies have shown that many patients with IBS experience pain in the rectum at a different threshold level than people who do not have the disorder. It is thought that this difference in pain perception is the result of a process in which the nerves of the gut become over-sensitized to stimulation.

Inflammation

By definition, IBS does not present with visible inflammation. While inflammation is not visible during routine diagnostic testing, it may still be involved. The evidence is beginning to be seen of the possibility of low-grade chronic inflammation on a cellular level in some individuals who suffer from IBS. This inflammation is thought to most likely be associated with cases in which IBS which was preceded by a bout of gastroenteritis, a condition classified as post-infectious IBS (IBS-PI).

Gut Bacteria

Although not as clear-cut as it sounds, the complicated nature of gut bacteria are most easily understood when classified as good bacteria (such as probiotics), and bad bacteria (those associated with infection and inflammation). Research focus on gut bacteria has begun to offer some evidence that there is a difference between the bacterial makeup of some IBS patients and those who do not have the disorder. Particular attention has been given to the role of bacteria in the small intestine as a contributor to IBS, namely, small intestine bacterial overgrowth (SIBO).

Hormones

Women are more likely to have IBS, which implies that changes in hormones play a role in developing IBS. Consequently, many women find that their IBS symptoms are worse during or around their menstrual cycles.

The Brain-Gut Connection

The digestive system has a sort of brain of its own, the enteric nervous system. This network of nerves directs the processes of digestion and is in close communication with the brain. This interaction is seen most clearly during the stress response. There is evidence that dysfunction in the interactions between the gut and the brain may underlie the motility disturbance and visceral hypersensitivity that result in IBS symptoms. This dysfunction is thought to be related to an imbalance in levels of particular neurotransmitters, which is why people with IBS often find relief from symptoms when taking antidepressants that target specific neurotransmitters.

IBS also is more common in people who have anxiety, depression, and other mental health issues. A history of physical, sexual, or emotional abuse also increases the likelihood of IBS.

Genetics

Initial research studies suggest that there is a genetic component of IBS as well, since IBS tends to run in families. Although a hereditary link has not been found, researchers have discovered that genes may play a role in the development of IBS.

According to a study featured in Gastroenterology, some people with IBS have a specific genetic defect (mutation) of the SCN5A gene that causes their condition. When this mutation is present, it causes people to experience a disruption in bowel function. During the initial study, researchers found that this gene mutation was present in 2.2 percent of IBS patients. Later, these results were confirmed in a genome-wide association study. Further studies of the genes associated with IBS may help point to the underlying causes of the condition.

Lifestyle Risk Factors

Smoking, drinking alcohol, obesity, lack of exercise, and poor diet can increase IBS flare-ups. Maintaining a healthy lifestyle may help prevent exacerbations of your condition.

It is no secret that stress can wreak havoc on your body. In fact, the body's stress response, as well as feelings of anxiety and depression, also can impact the development of IBS. This stress response is sometimes referred to as the brain-gut connection. Learning to deal with stress may help prevent exacerbations.

A Word From Verywell

When comes to an IBS diagnosis, it can be frustrating to try to cope with an issue when you do not know the exact cause for your condition. But, by reading more about IBS and talking regularly with your doctor, you will find ways to deal with the condition and still live a normal, active life. Eventually, you will discover things that work for you—whether it is meditation to relieve stress, adhering to a special diet or a combination of the two. Once you reach that point, your IBS will just be something you live with and not something that controls your life.

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