IBS or Irritable Bowel Syndrome is a disorder that is characterized by abdominal discomfort or pain. The eventual diagnosis depends on the presence of at least two of the following additional signs and symptoms in the last 3 months:
- Relief of the pain or discomfort after a bowel movement
- A change in how often a person has a bowel movement
- A change in characteristics of the stool. This change can be a change in consistency (loose versus hard), color (darker brown, yellowish, covered in mucus) or size (small lumpy stool versus a single large stool)
- Abdominal bloating
The pain or discomfort associated with IBS varies from one individual to the next, but is usually located at the lower abdomen. The pain or discomfort can be cramping and irregular or it can be constant. IBS most commonly begins in adolescence or when a patient is in their 20s but can occur in older adults. 
As a bit of an aside, the term “syndrome” is used because at this point, since we do not understand the cause of IBS, we can only describe it as a group of symptoms that generally occur together and form a set of criteria by which a physician can diagnose IBS. There is no single diagnostic test that can diagnose IBS, so this group of symptoms is the primary criteria used. The set of signs and symptoms described above is called the Rome III Criteria. Generally speaking, IBS is diagnosed by the Rome III criteria and the patient’s account of their history. Lab tests may be done, but these are often done to exclude other disorders rather than to diagnoses IBS.
As another aside, IBS was probably first diagnosed or at least described in 1892 by a famous physician, William Osler, one of the founders of Johns Hopkins Hospital and Medical School. Dr. Osler used the phrase mucous colitis to describe IBS. Other terms that have been used are spastic colon, irritable colon, and nervous colon. William Osler, by the way, wrote one of the “premier” medical textbooks—it was first written in the same year he described IBS and has been in continuous use – with continuous updates—since then.
For more on The Signs and Symptoms of IBS, click here.
What Causes IBS?
There is no known cause for IBS. For many years, people with what we would now call IBS were thought of as having a psychosomatic disorder. Psychosomatic disorders are those that are caused or made worse by emotional or mental disorders, but historically it was a rather dismissive way of saying “it’s all in your head”. That said, emotional and mental factors such as grief, depression, anxiety and stress do play a significant role in IBS, but do not cause IBS. Traditional and newer theories of IBS generally are seen as a three-part complex:
- Changes in intestinal motility: this includes changes in motility in both the small and the large intestines. These changes in motility can be correlated to the types of IBS (see below)
- Heightened sense of pain or discomfort. In general, people with IBS feel bowel distention with smaller amounts of gas or fecal contents.
- The co-existence of some mental or psychological disorder that can range from very mild to more severe, though this is relatively poorly understood because people with mental or psychological disorders tend to be more inclined to seek medical attention as compared to those without any mental or psychological disorders—and it may be that IBS is more commonly diagnosed in those with other health concerns.
Studies indicate that, world-wide, the prevalence of IBS is estimated to be 10-20%. In Western countries, women tend to be 2-3 times more likely to develop IBS. In India, however, men are about 70-80% of all IBS patients, though overall, India has relatively few IBS patients. IBS tends to develop before the age of 35 in most cases, but can develop after 40. Use of the Rome III criteria tends to result in lower reported rates of IBS. As a generality, communities and cultures where there is a level of higher perceived stress, lower quality of life and fewer barriers to accessing health care will report higher numbers of IBS diagnoses, but IBS exists in every country of the world with the higher rates appearing in Nigeria, Iceland, England, Ireland, Greece, Russia, Columbia, Peru, Brazil, the US, New Zealand, Pakistan, South Korea and Malaysia. The risk of IBS increases if someone in the family has been diagnosed with IBS.
The coexistence of depression, anxiety, PTSD or panic disorder has already been mentioned, but IBS is also associated with other disorders—about half of people with IBS also have fibromyalgia, chronic fatigue syndrome, chronic back pain, chronic pelvic pain, chronic headache, and temporomandibular joint dysfunction.3 It is not known why these disorders are associated with IBS, but there are certain shared characteristics—mainly the presence of pain or fatigue.
There are a number of theories that researchers can use to try and understand IBS better. In the long run, IBS will likely be caused by a combination of the following because not everyone with IBS has every possible characteristic of all of these.  For more information, see Causes of IBS.
- Brain-Gut Mis-communication: The brain and the gut are both highly enriched with communication networks. In fact, the gut has been called our “Second Brain” because of its rich nerve supply that is in many ways independent of the “first” brain. If these two nerve networks do not communicate effectively, the thinking is that IBS can be the end result.
- Motility problems in the gut. Motility is controlled by the brain and by the gut (mesenteric) nervous systems. This motility is mainly the process of peristalsis. Peristalsis are the wavelike contractions that pushes food and eventually waste through the intestines. Slowed motility can lead to constipation while faster motility can result in diarrhea. About 33% of people with IBS have evidence of disruption of gut motility.
- Sensitivity to Pain and/or discomfort. This difference in sensitivity can be due to how the nerves interact, personal and cultural differences. The upshot is that different people perceive pain in different ways. In people with IBS, there is also evidence that the nerves of the gut are in fact more sensitive to foods, gas and waste passing through the intestines—and the brain perceives this as discomfort or pain.
- About 1 in 7 people with IBS have what is technically known as postinfectious IBS which is a form of IBS which follows an infection of the digestive system. This infection can be viral, bacterial or protozoal. Some people with IBS have had a history of infection with a protozoa known as Giardia lamblia that causes a condition often known as beaver fever, an infection associated with diarrhea and is found throughout the world. Giardia is also associated with chronic fatigue syndrome, a syndrome that often coexists with IBS.
- Small Intestinal Bacterial Overgrowth. The large intestine is normally populated with a large and diverse set of bacteria. Normally, however, there should be very few bacteria in the small intestine where most of the absorption of nutrients from food takes place. Small intestinal bacterial overgrowth (SIBO) is the increased number of bacteria or a change in the types of bacteria in the small intestine. These bacteria can produce extra gas and possibly toxins which can cause the symptoms of IBS.
- Altered Levels of Chemical Messengers (Neurotransmitters and Hormones). There are a number of chemical messengers which appear to have altered levels in IBS. Reproductive hormones appear to affect IBS as well—changing levels of reproductive hormones during the menstrual cycle can affect the symptoms of IBS.
- Family history or genetics. While there haven’t been any specific genes that have been associated with IBS. IBS tends to be more common in some families than others.
- Food Sensitivities. Many people with IBS report sensitivity or intolerance to certain foods, including gluten, casein, carbohydrates, spices, fatty foods, coffee or alcohol. It is not certain if these sensitivities are involved in the causes of IBS or a result of the effects of IBS.
- Poor absorption of foods. There is some evidence indicating that simple and/or complex carbohydrates may not be well absorbed in people with IBS. Some people with IBS also may have problems with their gall bladder and the production of bile acids. These bile acids are required for the absorption of dietary fat.
- Mental health issues are also often found commonly in people with IBS. These mental health issues can include depression, anxiety, panic disorder and post- traumatic stress disorder (PTSD). It is not clear how or why these may be associated with IBS.
The Forms or Types of Irritable Bowel Syndrome
IBS is characterized as a functional disorder which is a type of condition that disrupts the normal function of an organ or system, but in which no changes in cells or tissues can be determined. In other words, all the lab tests come back normal, but someone with IBS has the abdominal pain and discomfort of IBS with all the characteristics (ie. relief after a bowel movement, changes in bowel habits etc.). In practice, this meant that people with IBS ended up going from one doctor to another with their symptoms sometimes dismissed as being reflective of hysteria, need to seek attention or some form of mental disorder. In recent years, getting an appropriate diagnosis has gotten easier, but is often still a problem unless you see a gastroenterologist, a specialist in intestinal disorders.
There are four sub-types of IBS. These are:
- IBS-D where Diarrhea is the dominant functional disruption
- People with IBS-D have, for example, faster transit times—meaning that the amount of time that food remains in the small and large intestine is shorter than normal and may have a sort of disconnect in the gut motility in relationship to their meals—the gut motility, for example, may increase too soon after a meal.
- IBS-C where Constipation is the dominant functional disruption
- People with IBS-C tend, on the other hand, to have longer transit times, but they also display similar disconnects as related to meals and gut motility.
- IBS-M is a “mixed” where both diarrhea and constipation are present
- IBS-A is an alternating form where the functional disruption is diarrhea alternating with constipation.
However, people originally diagnosed as, for example, IBS-D can switch to IBS-C—in fact, about 29% pf patients do just that within the first year. 75% of all patients change their particular subtype, also within the first year of diagnosis.
Tests and Diagnosis
As mentioned, there is no single test for IBS. Generally, lab tests may be done, but they are often done to exclude other possibilities. Depending on your specific sets of needs, signs and symptoms, you might get tested for various disorders of the digestive system such as disorders of the gallbladder, liver, or pancreas. You might also be tested for various infections—these can include viral, protozoal (eg. Giardia) or bacterial. Women may be tested for endometriosis. Both men and women might get tested for thyroid and adrenal gland function. Other disorders that are sometimes tested for include colon cancer and other cancers of the digestive tract, food sensitivities such as lactose, fructose or gluten intolerance, inflammatory bowel disease or IBD (quite different than IBS, though these are often confused), and various metabolic imbalances. Finally, your physician may look at any medications you may be on—there are a number of medications that can cause IBS-like symptoms. These include:
- Most of the cholesterol lowering statin drugs, including simvastatin, lovastatin, and atorvastatin (Lipitor®)
- Most heartburn medications. These include: omeprazole (Prilosec®), Nexium®, Prevacid®, pantoprazole (Protonix), cimetidine (Tagamet®), ranitidine (Zantac®).
- The bisphosphonates, used to prevent or treat osteoporosis. This includes drugs like alendronic acid(Fosamax®), zoledronic acid (Reclast® or Zometa®)
- Many antibiotics
- Non-steroidal anti-inflammatory drugs (NSAIDS) like ibuprofen (Advil®) and naproxen (Aleve®).
- Anti-histamines such as Allegra®, Zyrtec®, or Claritin®
- Antidepressants: especially tricyclic antidepressants such as amitryptiline (Elavil®) and imipramine (Tofranil®)
- Calcium channel blockers to control blood pressure, atrial fibrillation (A-fib) or migraines. These include drugs such as diltiazem (Cardizem®), nifedipine (Procardia®), amlodipine (Norvasc®) and verapamil (Covera® or Calan®)
- Antispasmodics to help relieve muscle spasms. These include Dicyclomine(Bentyl®) and hyoscine (Buscopan®). Many may recognize both of these medications as they are often used to treat
- NEVER stop taking any medications without talking to your physician first. It is worthwhile to discuss the possibility that the medications are causing IBS symptoms, but there are alternative medications or alternative approaches available to you and you don’t want to risk making yourself worse – don’t try to treat yourself!
Medical Treatment of IBS
Medical treatment may include some dietary approaches (see Best Diet for IBS) such as increasing fiber, drinking enough water, avoiding certain foods and beverages and watching for specific food problems. Primarily, the medical treatments for IBS include a number of different medications including anti-spasmotics, antidiarrheals, antidepressants, laxatives, various agents which block chemical messengers thought to be involved in the symptoms of IBS and others. For more, see Best Natural Treatments for IBS. Other approaches include cognitive-behavioral therapy, psychotherapy and hypnotherapy.4