Irritable Bowel Syndrome (IBS): Overview, Diagnosis, and Statistics

Irritable Bowel Syndrome (IBS) is a functional gastrointestinal disorder characterized by abdominal pain, bloating, and changes in bowel habits (diarrhea, constipation, or alternating). Symptoms must persist for at least 6 months for diagnosis. Subtypes: - IBS-D: diarrhea-predominant - IBS-C: constipation-predominant - IBS-M: mixed/alternating Diagnosis: Based on symptoms and exclusion of other conditions (celiac disease, inflammatory bowel disease, infections, malignancy). Rome IV criteria require recurrent abdominal pain at least one day per week over three months. No specific lab test can confirm IBS — standard scans, biopsies, and blood tests appear normal because IBS is a disorder of gut function, not structure. Causes (multifactorial, no single known cause): - Gut-brain axis dysfunction and abnormal serotonin metabolism (~90% of body's serotonin is in the gut) - Stress and psychological factors (anxiety, depression, childhood trauma) - Post-infectious: ~10% of cases follow gastroenteritis - Gut microbiota alterations (dysbiosis) - Genetic predisposition Treatment categories: - Diet: Low-FODMAP (supervised), soluble fiber supplementation - Antispasmodics: dicyclomine, hyoscyamine, mebeverine, peppermint oil - Antidepressants: tricyclics (amitriptyline) for pain modulation, SSRIs with limited evidence - Antidiarrheals: loperamide (Imodium) for IBS-D - Antibiotics: rifaximin for IBS-D with SIBO component - Psychological therapies and regular physical activity Statistics: - Global prevalence: ~11.2% (10-15% in developed nations) - Twice as common in Western women as men - Typically presents before age 45 - Does NOT affect life expectancy or cause serious disease progression - US economic impact: $1.7-10 billion direct costs, $20 billion indirect costs annually