What causes IBS - Irritable Bowel Syndrome?

IBS root causes

Irritable bowel syndrome – an overview

Irritable bowel syndrome affects the digestive tract and is associated with a disturbed interaction of the intestinal-brain axis and immunological processes.

It depends on various factors whether an irritable bowel develops. For example, food intolerances, infections, psyche.

Typically, abdominal pain occurs, accompanied by constipation, diarrhea or an alternation of both and/or flatulence.

The diagnosis is made by the physician when a typical complex of complaints is present and other causes such as an infectious or chronic inflammatory bowel disease have been ruled out.

The therapy depends on which symptoms predominate and which causes play a role. A change in diet often helps. Medications and psychological methods are also used.

Definition: What is irritable bowel syndrome?

According to current understanding, irritable bowel syndrome is a disorder of the intestinal-brain axis. The interaction of the intestinal nervous system ("abdominal brain") with the central and autonomic nervous system is thus altered (more on this in the Causes section).

It is difficult to say how common irritable bowel syndrome really is, since studies on its frequency have come to very different conclusions. However, about ten percent of people worldwide may be affected. Irritable bowel syndrome can resolve spontaneously, but is often chronic. More women than men are affected.

Doctors speak of irritable bowel syndrome when...

...patients report abdominal pain and other intestinal complaints such as flatulence for at least three months and if they have altered bowel movements.

...the symptoms significantly reduce quality of life and the patient is seeking help because he or she is concerned about health.

... very probably no other diseases are responsible for the symptoms.

...the symptoms occur at least once a week.

Irritable bowel syndrome often occurs together with other diseases. These include:

  • Chronic fatigue syndrome (ME/CFS)

  • Fibromyalgia syndrome

  • Irritable stomach (functional dyspepsia)

  • Tension headaches

  • Depression

  • Anxiety disorders

  • Eating Disorders

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Causes: How does Irritable Bowel Syndrome IBS develop?

IBS develop cause

Irritable bowel syndrome is a disease with many faces. It is possible that there is not "the" irritable bowel, but several subgroups. This is supported by the fact that researchers have now identified several irritable bowel subtypes in which the main complaints differ.

Secondly, different triggers could be possible, which in turn trigger different pathogenic mechanisms in the intestine. Irritable bowel syndrome may also occur as a concomitant of other diseases (see Definition section). However, there is increasing evidence as to which mechanisms in the body may play a role in the symptoms of irritable bowel syndrome.

Primarily, IBS is probably a disorder of the gut-brain axis, but immunological processes also have their part to play.

The gut-brain axis

The autonomic nervous system is the part of the nervous system that controls many bodily functions without our conscious influence. It connects the central nervous system (located in the brain and spinal cord) with the peripheral nervous system (flowing through the body) and consists of an activating part, the sympathetic nervous system, and a calming part, the parasympathetic nervous system.

The third autonomic nervous system is the intestinal nervous system, whose functions are also involuntary. Mainly via the so-called vagus nerve, which belongs to the parasympathetic nervous system, the intestinal nervous system, central nervous system and autonomic nervous system communicate actively with each other via messenger substances. This is also referred to as the gut-brain axis.

Experts suspect that the intestinal nervous system, also known as the abdominal brain, is dysregulated in irritable bowel patients. For example, many studies have shown increased activity of the sympathetic nervous system and decreased activity of the parasympathetic nervous system. This could cause the abdominal discomfort, explain the co-occurrence with other diseases and also influence the psyche.

Psychological influences, biopsychosocial model of disease

Studies show that in people with irritable bowel syndrome, certain brain areas are altered in which emotional processes, but also processes controlling behavior, are processed. Affected people also perceive sensations in the abdomen as painful more quickly, tend to evaluate these sensations as symptoms of an illness, and worry more that something bad could be behind them. Since irritable bowel syndrome is often not diagnosed by a doctor, the examinations is detected and patients often do not feel taken seriously, fear and uncertainty can be exacerbated.

Some researchers suspect: Diseases such as irritable bowel syndrome could arise from an interplay of biological, social and psychological factors. They refer to this as the biopsychosocial disease model, which could also explain diseases such as fibromyalgia and chronic fatigue syndrome. In relation to irritable bowel syndrome, this model could mean, for example: A person did not get the love, attention, and support from their parents as a child that they needed.

This has a negative effect on the psyche, the autonomic nervous system and development. The person has adopted behaviors such as perfectionism, drive for success, excessive helpfulness because of their childhood, which leads to chronic stress and can negatively affect bowels and other organs. At the same time, the person may move in an unfavorable social environment, have stress with the partner, at work.

Then they get a severe gastrointestinal infection or eat too often highly processed or carbohydrate-rich foods and exercise too little. The interaction of all these events then eventually leads to the person getting irritable bowel syndrome. However, this is just a fictional example to illustrate: Many different influences contribute to the development of irritable bowel syndrome.

Patients with irritable bowel often have pain in other organs / body regions (for example tension headache, back pain, fibromyalgia syndrome) and depressive or anxiety disorders. However, the disease is not a psychological condition.

Increased sensitivity to pain, changes in the intestinal nervous system

The gastrointestinal wall is crisscrossed by a dense network of nerve fibers. These include pain fibers. Some patients react to what are actually normal intestinal movements such as stretching and squeezing with pain because their nervous system is sensitized, i.e. it reacts earlier to such stimuli with pain. Certain food components can also trigger a pain stimulus by chemical means.

It is not possible to say exactly whether the function of the nerve fibers is impaired. However, the messenger substances that convey signals between the intestinal nerve fibers and between the intestine and the brain are altered in their numbers. In particular, the messenger substance serotonin, over 90 percent of which is produced in the intestine, appears to play an important role in irritable bowel syndrome and is sometimes decreased or increased.

Serotonin, actually known as the happiness hormone, controls intestinal movements and other functions together with other messenger molecules.

Impaired intestinal barrier, immune activation

Some patients probably have an impaired intestinal barrier. Normally, tight junctions between the intestinal mucosa cells ensure that only certain substances, especially nutrients such as protein, fat, vitamins, carbohydrates, can pass through the intestinal mucosa. If these connections (so-called tight junctions) are somewhat more permeable, other substances can also penetrate the mucosa, which may activate the intestinal immune system.

Around 70 to 80 percent of all immune cells are located in the intestine. The activated immune system could cause a "silent" inflammation, i.e., one that is hardly measurable with medical procedures, which contributes to the symptoms. Some food intolerances that play a role in irritable bowel syndrome could also arise in this way. If the body's own defenses are stimulated in the intestines, this can have an effect on the entire organism.

Genetic influence

Certain gene alterations increase the likelihood of IBS when other factors are added.

Altered intestinal flora

People with IBS have altered intestinal flora compared to healthy individuals. In some cases, other bacterial strains are more prevalent than in healthy people, and in some cases there are fewer different species. Antibiotics, gastrointestinal infections and chronic stress can lead to altered intestinal flora, but so can other factors. Studies also show that some patients have too many bacteria in the lower small intestine (small intestinal bacterial overgrowth, SIBO), where they do not normally belong. Exactly what role the intestinal flora plays in irritable bowel syndrome requires further research. The same applies to whether an altered bacterial composition is the cause or consequence of the intestinal disease.

Intestinal infections as a trigger

Especially in people whose irritable bowel leads to diarrhea, the cause may be a gastrointestinal infection that may have occurred weeks, months or even years ago. How viruses, bacteria or other pathogens trigger irritable bowel syndrome is not yet entirely clear. It is possible that they permanently activate the intestinal immune system.

Bile acid metabolism out of kilter

People whose irritable bowel syndrome is more likely to be accompanied by diarrhea have a disturbed bile acid metabolism in up to 50 percent of cases, according to the doctors' guidelines. There are then more bile acids in the lower small intestine than can be reabsorbed there. As a result, more acids enter the large intestine, which can lead to diarrhea.

Disturbed intestinal movements

Normally, the intestinal muscles move rhythmically to transport the intestinal contents. In irritable bowel syndrome, intestinal movements may be altered: either intestinal contents move more slowly, resulting in constipation, or more rapidly, resulting in diarrhea. A number of disorders of digestive activity can cause irritable bowel-like symptoms, but are disease patterns in their own right.

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