Pathophysiological Mechanisms and Nonpharmacological Interventions in Irritable Bowel Syndrome: Current Insights and Future Directions.

Irritable bowel syndrome, diagnosed using the ROME IV diagnostic criteria, is one of the most common dysfunctional disorders of the gastrointestinal system with a high global prevalence. Although symptom presentation is diverse, symptoms primarily manifest as abdominal pain, bloating, and alterations to bowel habits, negatively impacting quality of life but without an associated increase in mortality risk. Disruptions to the gut-brain axis, the bidirectional communication system between the central nervous system and the enteric nervous system, are hypothesised to be at the core of irritable bowel syndrome. Dysfunction may also be associated with stress and anxiety, as well as dietary factors, among other aspects related to physical and social environment, genetic predisposition and medical history. Patients with irritable bowel syndrome have also demonstrated increased vulnerability to neurotransmitter imbalances, with abnormalities associated with changes in gastrointestinal motility, low-grade inflammation and visceral pain. Moreover, chronic stress and anxiety may significantly exacerbate symptoms through the upregulation of cortisol secretion, disrupting the gut microbiome and elevating visceral sensitivity. While the gut microbiome maintains the integrity of the gut-brain axis and intestinal barrier, decreases in its diversity heighten susceptibility to intestinal inflammation. Although there is currently no known cure for irritable bowel syndrome, research supports stress management and behavioural therapies, a low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet, and probiotic supplementation as key interventions to alleviate symptoms. Additionally, faecal microbiota transplantation emerges as a promising intervention that addresses some of the limitations in current interventions. This literature review explores the pathophysiological mechanisms relating to irritable bowel syndrome, with insight into current interventions and future directions to directly address the underlying factors driving symptomology.