A 2021 analysis involving over 250,000 participants found a strong genetic overlap between IBS and mental health conditions including anxiety, neuroticism, depression, and schizophrenia. The study also found that GAD-7 anxiety scores (indicating mild levels of anxiety) correlated with IBS severity.
It is well established that IBS patients are more likely to suffer anxiety and depression. The theory was that emotional factors might trigger IBS symptoms, or that chronic gut symptoms were leading to mental duress. But the newly discovered genetic overlap between the two conditions suggests a shared cause of development rather than one simply causing the other.
The study also noted the possibility of underlying neurobiological factors in IBS, such as the potential relevance of neuronal dysfunction of the central nervous system (CNS) and the enteric nervous system (ENS).
So, what exactly is the connection between the gut, the brain, and the nervous system when it comes to IBS?
Stress & IBS: An Overview
IBS is known as a functional bowel disorder, defined by recurring abdominal pain, bloating, and altered bowel habits. As a majority of IBS patients also show elevated levels of anxiety and neuroticism, IBS is believed to be a disorder of the gut-brain axis.
This means that IBS symptoms are driven by the complex interaction between 3 main players:
- Dysregulated central and enteric nervous systems
- Altered signals in the brain-gut axis
- A gut microbiome out of balance (gut dysbiosis)
The Enteric Nervous System: The First Brain
Sandwiched between layers of the mucosa is a vast network of enteric neurons and neurotransmitters, making up the enteric nervous system (ENS). Many call the gut the ‘second brain’, but evidence suggests that before sentient life developed the central nervous system, it already had an enteric nervous system some 650 million years ago. This would make the ENS the very first brain.
The ENS governs the digestive system, orchestrating motility, secretion, and blood flow. It is also connected to the spinal cord, brainstem, and central nervous system (CNS). Although the ENS is able to function independently from the CNS, the CNS has a strong modulatory role in regulating intestinal function.
The two systems communicate bi-directionally through the vagus nerve, amongst other nerves and pathways. This communication system is what we now call the ‘brain-gut axis’, and it plays a monumental role in IBS.
How Stress Triggers and Worsens IBS Symptoms
Due to the bidirectional communication between the gut and the brain, certain stressors on the brain, gut, immune system, or microbiota can cause alterations in the way the body responds to signals, resulting in psychiatric and/or gut symptoms.
In IBS, abnormalities in brain-gut communication can cause the following digestive symptoms:
- Altered intestinal motility and transit time
- Altered fluid secretion/absorption
- Visceral hypersensitivity
- Altered microbiome composition
- Increased intestinal barrier permeability
IBS patients may also have to contend with certain mood and functional brain alterations, including anxiety based on sensory input from the gut, worsened symptoms of depression potentially due to neurotransmitter dysfunction, anger, brain fog, impaired judgment, and difficulty concentrating.
The Role of Stress Hormones in IBS
While gut and mood symptoms in IBS may stem from a shared genetic component, the two systems do appear to feed off each other in a toxic cycle, with worsened gut health exasperating mood symptoms, and vice versa.
One of the main factors in this cycle is the cortical corticotropin release hormone (CRH), which is found in elevated levels in IBS patients. During stressful periods, the hypothalamus releases CRH. This signal is picked up by the pituitary gland, which is prompted to send out the adrenocorticotropic hormone (ACTH) to the adrenal glands, which in turn releases cortisol.
But when the HPA axis is over-activated, as reported in IBS patients, the excess cortisol secretion can directly worsen IBS symptoms – especially stomach cramps.
This is because cortisol is a glucocorticoid hormone, and we have glucocorticoid receptors in all tissues in our body, including the gastrointestinal tract. So not only does cortisol impact the nervous and immune systems, but it can cause inflammation in the digestive tract, damage to the intestinal muscles, and colon spams.
All this merely highlights the need for stress management in IBS alongside the treatment of digestive symptoms.
Managing Stress & IBS
The emerging evidence of the bidirectional relationship between the gut and brain in IBS has led to new approaches in treatment, including mindfulness and meditation, behavioral intervention, and dietary approaches. Cognitive behavioral therapy (CBT) appears especially promising in reducing IBS symptoms.
CBT is an intervention that teaches information processing skills to address the psychological factors exasperating abdominal symptoms. These psychological factors would include intense worry, stress reactivity, catastrophizing, maladaptive coping, and hypervigilance to perceived threats.
A 2021 RCT on IBS patients found that CBT can and does reduce IBS symptom severity. Following the treatment, the patients who responded showed improvements in symptom severity, abdominal pain, and life satisfaction. The patients also showed a reduction in connectivity between multiple cortical networks, including networks responsible for emotion regulation.
Using the Mind to Heal the Gut
The study mentioned above also found that patients who responded to CBT showed higher levels of Bacteroides in their microbiome, suggesting that the gut microbiome is responsive to “top-down” signals from the brain. This is in line with a recent study on Buddhist monks who, after years of daily meditation, showed enriched amounts of Prevotella, Faecalibacterium, and Bacteroides compared to the control group.
This means that as much as healing the gut can benefit mental health, cognitive, behavioral, and mindfulness approaches to stress relief appear to have a direct positive impact on the gut in cases of IBS.
Herbal Treatments for Body & Mind
Certain herbal adaptogens have also shown promise in both relieving stress and IBS digestive symptoms. Ashwagandha may be especially helpful for IBS patients, as it works through multiple mechanisms to block stress signals and reduce stress hormones that trigger a sensitive digestive system.
Ashwagandha may be able to reduce the force of an overactive HPA axis, leading to reduced serum cortisol levels. Ashwagandha also has the ability to imitate a neurotransmitter called GABA, which occurs naturally in the body to block stress signals and calm the entire system. As low levels of GABA are associated with abdominal pain in IBS patients, this mechanism may alleviate both digestive discomfort and stress.