A woman is nervously biting her nails. The same woman in also shown with her eyes closed, holding her stomach. Behind both figures are two arrows showing a cyclical effect.

Mental Health and IBS

Irritable bowel syndrome is characterized by chronic abdominal pain and altered bowel habits. It can be a painful condition linked with higher levels of stress, anxiety, and depression. The development of IBS is linked to things such as:1,3-4

  • Altered hypothalamic-pituitary-axis (HPA axis) function. The HPA axis is the stress response system which links the central nervous system (our brain) and the endocrine system.
  • Abnormal functioning of the gut-brain axis has been reported in people with IBS. The gut-brain axis is the communication system that links the emotional, thinking, and reasoning parts of the brain with the intestine.
  • Abnormal gut motility; Gut motility is the contractions of the muscles in the gastrointestinal tract, it helps to move food through the gut.
  • Imbalanced gut microbiome. The microbiome is the eco-system of bacteria and other organisms that live in the human gut.
  • Psychological stress has been shown to affect motility and to increase the sensitivity of the internal organs (known as visceral hypersensitivity) within the body, such as the stomach or intestines. Some studies have linked IBS to childhood trauma.
  • A previous infection such as gastroenteritis can trigger IBS. This is often referred to as post-infectious IBS.
  • People with IBS may have altered immune system function. Studies have shown with increased levels of cytokines, which are signaling molecules which stimulate other immune cells to move towards areas of inflammation or infection.
  • Genes or family history of IBS may increase your risk of developing IBS.
  • Psychosocial stress, which can be described as a life situation which creates an intense level of stress that can contribute to the development of a mental disorder such as anxiety.

Many of these things imply that mental health may play a role in the development and maintenance of IBS.

What brain imaging studies show

Patients with IBS show differences in brain structure. In fact, research has demonstrated that patients with IBS have slight structural changes in parts of the brain that are involved in sensing pain and stress.1

How do anxiety and stress affect the gut?

The autonomic nervous system is a part of the nervous system that regulates processes of the body such as heart rate, blood pressure, and digestion. It is divided into three components:2

  1. The parasympathetic nervous system, which is known as the rest and digest system. It is in charge of functions such as digestion, urination, and defecation.
  2. The sympathetic nervous system, which is the fight or flight response. Stress or anxiety will activate this part of the nervous system. When activated it stops digestion, increases heart rate, and sends blood into your muscles.
  3. The enteric nervous system controls the activities of the gut. Dysfunction of the enteric nervous system has been implicated as an underlying cause of IBS.

Having persistent high levels of stress, anxiety or depression can lead to disturbances between the brain and the gut. This can trigger overactivity of the gut leading to diarrhea. Others may experience slow transit time of food through the gut which causes constipation and gas.2

It’s estimated that over half of people with IBS have a mental health disorder such as anxiety or depression.1 Additionally, stressful and traumatic events such as the loss of a family member or relationship breakdown can worsen IBS symptoms.

Stress and anxiety can have the following effects on the gut:3

  • It changes gut motility which can lead to constipation or diarrhea
  • Increases organ sensitivity
  • Changes the natural secretions from the digestive system which can impair digestion
  • It can increase the gap between the intestinal cells. This is referred to as a leaky gut and is linked to a range of conditions and symptoms.
  • Prevents blood flow to the gut and impairs the ability for the cells in the gut to regenerate
  • It has negative effects on the gut microbiome
  • High levels of stress activate the immune system to release cells that cause inflammation
  • All of the above changes can cause IBS symptoms and for someone who has excessive stress, their IBS can get worse as a result.

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