Butterflies in My Stomach: The Brain-Gut Axis
Ever had that horrible sensation of butterflies in your stomach before giving a speech? If so, then you have experienced one of the common ways in which the brain interacts with the gut to influence our thoughts, feelings, and perceptions. In fact, the brain and gut are inextricably linked, to the point that we often don’t realize the important role this link plays in our psychological health. Disorders such as Irritable Bowel Syndrome and Functional Constipation illustrate how important the role of our thoughts and feelings are on our gut function. In this article, the link between the brain and the gut in our physical and psychological wellbeing will be discussed.
The Brain-Gut Axis
The Brain-Gut axis describes a network of neurons that connect the human enteric nervous system (ENS) with the central nervous system (CNS). The ENS consists of a series of neurons that exist within the gastrointestinal tract, and which govern visceral sensation and perception, as well as the secretion of various chemicals into our gut. Comparatively, the CNS consists of a wide range of neural networks and fibers that interact within higher cortical regions to govern our thoughts, feelings and emotions, as well as basic physiological processes such as those involved in homeostasis.
The link between the brain and the gut is thought to play a major role in a group of disorders known as the functional gastrointestinal disorders. These disorders include a variety of gastrointestinal symptoms that have no single unifying patho-physiological cause, and which are associated with various psychological symptoms including anxiety, low mood, and heightened visceral sensation.
Irritable Bowel Syndrome
Arguably the most common functional gastrointestinal disorder is Irritable Bowel Syndrome (IBS). IBS is a disorder involving chronic abdominal pain and discomfort, and altered defecation habits including diarrhea and constipation. Patients with IBS often have a heightened sensitivity to visceral sensations and are more likely to perceive stomach pain than those without the disorder. Further, the role of psychological processes such as stress and anxiety is such that these symptoms tend to exacerbate symptoms of IBS. Patients with this disorder are often immensely frustrated at the prospect of being diagnosed with a disorder that has no specific physical cause.
The Link between Stress, Anxiety, and Gut Sensation
Returning back to our example of butterflies in the stomach before giving a presentation — let us explore what is happening at the biological and psychological levels here. In response to stress, the brain releases the stress hormone known as cortisol; the release of which is a hallmark of sympathetic nervous system activation, which characterizes our bodies “fight-flight-freeze” response. In response to the release of cortisol, activity within our gut mucosa changes, which corresponds with alterations in the normal speed of digestion once the sympathetic nervous system is activated. These changes in gut mucosa activity make us more vulnerable to experiencing pain and discomfort, and this heightened sensitivity normally recedes once the initial psychological stressor disappears and the body’s parasympathetic relaxation response kicks in.
For individuals who experience stress and anxiety at a chronic and clinical level, however, the sympathetic nervous system is constantly active and thus the gut undergoes various neuro-endocrine changes which make the gut mucosa more reactive to stress, and thus more sensitive to the transmission of pain signals to the brain in response to normal visceral sensation. This in part explains why functional gastrointestinal disorders such as IBS are so commonly co-morbid with psychological disorders such as generalized anxiety disorder and major depressive disorder.
Due to the interplay between psychological and physiological factors in brain-gut disorders such as IBS, researchers have aimed to treat these disorders with therapies that are typically used for mental health concerns. Indeed, cognitive-behavioral therapy; which is a common and evidence-based psychological therapy, is effective in reducing symptom distress and symptom severity in patients with IBS and other functional gastrointestinal disorders. This corresponds with the relative efficacy afforded by antidepressants such as the selective serotonin reuptake inhibitors. Thus changes in psychological activity in patients with IBS and associated disorders appear to correspond with changes in gut activity, and the heightened sensations that are associated with this activity.
Next time you experience butterflies in your stomach, stop and reflect on what might be happening in your body. Emotions are bodily based, and are as physical, as they are psychologically based. For patients with disorders such as Irritable Bowel Syndrome, there seems to be an inextricable link between physical and psychological factors in the experience of pain, discomfort, and bloating. IBS and associated disorders illustrate the important link between the body and mind in physical as well as mental wellbeing. Neither exists in isolation.
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