Understanding the Gut-Brain Axis
The gut-brain axis is a network of communication between our gastrointestinal (GI) system and our brain. It is bi-directional, just like a highway, where signals flow back and forth between the gut and the brain.
This connection is facilitated through various pathways, including:
The autonomic nervous system (the parasympathetic and sympathetic systems)
The enteric nervous system, often dubbed the "second brain" due to its network of over 500 million neurons capable of functioning independently of the brain
The gut microbiota, the trillions of microbes residing in our intestines, also play a role in this communication system
The hypothalamic-pituitary-adrenal (HPA) axis, which regulates the body's stress response by releasing hormones like cortisol and epinephrine (adrenaline), influencing gut function.
Disorders of the Gut-Brain Interaction
Disorder of Gut-Brain Interaction (DGBI) is a recent term that replaced the term “functional gastrointestinal disorders”. These conditions arise due to disruptions in the communication between the gut and the brain.
DGBIs are a group of disorders classified by GI symptoms related to any combination of:
Motility disturbance
Visceral hypersensitivity
Altered mucosal and immune function
Altered gut microbiota
Altered central nervous system (CNS) processing
Examples of DGBIs:
Irritable bowel syndrome (IBS)
Functional dyspepsia (FD)
Abdominal pain disorders
These disorders affect a substantial portion of the population, with estimates suggesting they impact up to 30–40% of individuals in Western countries, with a higher prevalence among women (1).
Differentiating from the Psychosomatic Perspective
Historically, these conditions were often viewed through a psychosomatic lens, where they were considered to be primarily psychological in nature, with physical symptoms manifesting in the absence of identifiable medical causes. However, the understanding of DGBIs has evolved, recognizing them as genuine physiological conditions rooted in the complex relationship between biological, psychological, and social factors.
Mental Health Conditions in DGBIs
35% of people with a DGBI also have anxiety and 10% have a mood disorder.
However, it's important to note that 50% or more of patients do NOT meet criteria for psychiatric disorders. This highlights the complexity of these conditions and underscores the importance of addressing them from a holistic perspective.
The Biopsychosocial Model of IBS
The biopsychosocial model gives us a basic understanding of the multifaceted nature of DGBIs, including IBS. It emphases the relationship between biological, psychological, and social factors in the development and management of these conditions. Effective management requires a comprehensive approach that addresses all three dimensions, tailoring treatment strategies to individual needs (2).
Biological Factors:
Intestinal permeability
Motility
Hypersensitivity
Immune dysfunction
Altered bacterial flora
Inflammation
Psychosocial Factors:
Stress
Psychological state (anxiety/ depression)
Ineffective coping strategies
Social support
Role of Stress in IBS Symptoms
Stress plays a significant role in the worsening of symptoms in IBS and other DGBI. The stress-IBS cycle involves a triggering event that leads to hypervigilance, visceral hypersensitivity, and the development of maladaptive behaviors, all of which contribute to symptom exacerbation and distress. Understanding this cycle is crucial in developing targeted interventions to break the cycle and alleviate symptoms.
Behavioral Patterns and Coping Mechanisms
Patients with DGBI often engage in various behavioral patterns and coping mechanisms in response to their symptoms. These may include checking behaviors, controlling behaviors, and avoidant behaviors. Examples of these include: limiting certain foods, checking to see if you’re bloated in the mirror, and avoiding social interactions (canceling plans). While these behaviors are an attempt to seek reassurance and manage symptoms, they actually exacerbate symptoms and perpetuate the stress cycle. Recognizing and addressing these patterns is essential.
Impact of Eating Habits
Eating habits can significantly influence symptoms in individuals with a DGBI. Factors such as the gastrocolic reflex, meal timing, and snacking habits can impact gastrointestinal motility and symptom severity.
Patients with IBS can have a stronger colonic response (overreaction) to the gastrocolic reflex due to their heightened visceral sensitivity. These patients may experience a strong urge to defecate following ingestion of a meal and may experience symptoms like abdominal distension, flatulence, and pain (3).
Psychological Interventions
Psychological interventions such as gut-directed hypnotherapy and cognitive-behavioral therapy (CBT) have shown promise in managing DGBI symptoms. CBT teaches us that our thoughts and behaviors can impact GI symptoms and teaches skills that can improve physical symptoms of IBS. This can include diaphragmatic breathing, countering negative thinking, and so forth. These approaches aim to address the underlying psychological factors contributing to symptom exacerbation and empower patients with coping strategies to improve their quality of life.
Questions? Let us know below.
Citations:
Sperber A.D., Bangdiwala S.I., Drossman D.A., Ghoshal U.C., Simren M., Tack J. Worldwide Prevalence and Burden of Functional Gastrointestinal Disorders, Results of Rome Foundation Global Study. Gastroenterology. 2021;160:99–114. doi: 10.1053/j.gastro.2020.04.014.
Jagielski C.H., Riehl M.E. Behavioral Strategies for Irritable Bowel Syndrome: Brain-Gut or Gut-Brain? Gastroenterol. Clin. N. Am. 2021;50:581–593. doi: 10.1016/j.gtc.2021.03.006.
Malone JC, Thavamani A. Physiology, Gastrocolic Reflex. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan.
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