Irritable Bowel Syndrome – Cannabis Research

Description of Irritable Bowel Syndrome

Originally termed mucous colitis by Sir William Osler in 1892, a digestive disease characterized by mucous diarrhea and abdominal colic, is known today as irritable bowel syndrome (Surawicz et al., 2007, p. 458).

Abbreviated as IBS, Irritable Bowel Syndrome is the most common condition within the family of functional bowel disorders characterized by recurrent abdominal pain, bloating, discomfort, and alteration in bowel habits (W. Chey et al., 2015; Alammar & Mullin, 2019). Depending on the nature of the bowel function, IBS is further categorized into four disease subtypes:

• Diarrhea predominant (IBS-D)


• Constipation predominant (IBS-C)


• Mixed (IBS-M)


• Unsubtyped (IBS-U).

Irritable Bowel Syndrome (IBS) is a chronic, functional gastrointestinal disorder of the large intestine, characterized by recurring symptoms without clear structural or biochemical abnormalities. Because IBS is considered non-inflammatory and largely idiopathic (of unknown cause), it is defined as a syndrome rather than a distinct disease.

Diagnostic Criteria: At present, irritable bowel syndrome has no pathognomonic blood tests, markers, or imaging studies. The diagnosis is based on characteristic symptoms using established criteria (Rome IV, 2016), exclusion of concerning features called “red flags”, and use of selected tests to exclude conditions that can mimic IBS (Alammar & Mullin, 2019, p. 440). Typical features (symptoms) of IBS include (W. Chey et al., 2015):

• Loose/frequent stools


• Constipation


• Bloating


• Abdominal cramping, discomfort, or pain


• Symptoms brought on by food intake or specific food sensitivities


• Symptoms are dynamic over time (change in pain location, change in stool pattern)


• The most common clinical method used for the diagnosis of IBS is the Rome IV Criteria for Irritable Bowel Syndrome (C1) in conjunction with stool characterization using the Bristol Stool Form Scale (BSFS).

Rome IV Criteria:

Recurrent abdominal pain on average at least 1 day/week in the last 3 months*, associated with two or more of the following criteria:

1. Related to defecation


2. Associated with a change in the frequency of stool


3. Associated with a change in the form (appearance) of stool.

*Criteria fulfilled for the last 3 months with symptom onset at least 6 months before diagnosis.

Stool patterns must be present greater than 25% of the time with Types 1 and 2 indicative of IBS-C, Types 6 and 7 for IBS-D, and Types 1 and 7 for IBS-M (Mearin et al., 2016).

Importantly, somatic causes of diseases with similar symptoms must be excluded, which are often the rationale for performing diagnostic studies for a condition that has no identifiable specific or pathognomonic findings.

Warning signs (“red flags”) for somatic causes of IBS-like disease (W. Häuser et al., 2012), (W. Chey et al., 2015):

• Diarrhea is the main symptom


• Fever


• Severe or progressively worsening symptoms


• Blood in the stool (rectal bleeding or melena)


• Unexplained iron-deficiency


• Weight loss of more than 10% despite unchanged food intake


• Nocturnal symptoms (diarrhea)


• Family history of colon cancer or other organic gastroenterological disease, including Celiac disease, or inflammatory bowel disease


• Onset of symptoms after age 50 years


• Brief history (<6–12 months) and/or progressive symptoms


• In the basic laboratory profile, anemia or signs of inflammation

Aside from concerning “red flags,” several medications, both over the counter (OTC) and prescription, can imitate or exacerbate IBS symptoms. OTC medications such as antihistamines, calcium, iron, magnesium, nonsteroidals, and wheat bran have potential bowel-related side effects and should be considered in the history obtained from the patient. Likewise, prescription antibiotics, antidepressants, antiparkinsonian drugs, antipsychotics, calcium-channel blockers, diuretics, metformin, opioids, and sympathomimetics can cause IBS-like symptoms. Some of the more notable “organic” conditions that can cause IBS-like symptoms or occur in association with IBS include celiac disease, microscopic colitis, the inflammatory bowel diseases (IBD), Crohn’s disease and ulcerative colitis, bile acid diarrhea, colon cancer, and dyssynergic defecation. One-third of patients with IBD fulfill Rome criteria for IBS (W. Chey et al., 2015).

Because IBS is a diagnosis of exclusion, a thorough clinical evaluation is important to rule out other gastrointestinal diseases such as IBD or celiac disease. Treatment approaches often require multimodal care, targeting both gut physiology and psychological well-being. 

The pathophysiology of irritable bowel syndrome has not been completely elucidated. Numerous causes have been proposed, none of which have been proven to be the sole cause of symptoms. According to Chey, both environmental and host factors contribute to the symptoms of IBS (W. Chey et al., 2015). The list of potential etiologic factors is extensive:

Environmental Contributors to IBS Symptoms

• Early life stressors (abuse, psychosocial stressors)


• Food intolerance/sensitivity


• Antibiotics (and other ingested xenobiotics)


• Enteric infection

Host Factors Contributing to IBS Symptoms

• GI dysmotility


• Altered pain perception


• Altered brain-gut interaction
  
  
  
  • Autonomic hyperactivity
  
  
  • Dysfunction of the hypothalamic-pituitary-adrenal axis
  
  
  
  


• Altered enteric neurotransmitters


• Dysbiosis (an imbalance between the types of organisms present in a person's natural microflora, especially that of the gut, thought to contribute to a range of conditions of ill health)


• SIBO (small intestinal bacterial overgrowth)


• Increased intestinal permeability


• Microscopic intestinal inflammation


• Bile acids


• Increased gut mucosal immune activation


• Visceral hypersensitivity


• Genetic predisposition


• Clinical Endocannabinoid Deficiency Syndrome


• Alterations in the Endocannabinoidome (eCBome)