How long-term stress impacts the intestine and your life

General Studies Paper 2

Context

• The crossroads of mental health and gastroenterology got a lot more attention in May this year, with a study published in Cell journal, titled ‘The enteric nervous system relays psychological stress to intestinal inflammation’.

The study

• Mental health profoundly impacts inflammatory responses in the body. This is particularly apparent in inflammatory bowel disease (IBD), in which psychological stress is associated with exacerbated disease flares.
• It’s an important study as for the first time we have a much clearer understanding of the possible underlying mechanisms of inflammatory response and the whole cascade which ultimately precipitates the disorder.
• This is good not only for researchers but also for clinicians, because the pathways have been quite well explained.

Stress fracture

• The study talks of stress pushing the adrenal gland to make glucocorticoids, a steroidal stress hormone.
• When stress is short-term, like before an exam, it may result in a loss of appetite and increased frequency of stools.
• When it’s chronic, or experienced long term, over a few weeks to months to years, like in a toxic job or marriage or through childhood with the pressure to perform, it can result in inflammation of the gastrointestinal tract, an example being inflammatory bowel disease (IBD).
• With chronic stress, the body is constantly producing glucocorticoids. Two mechanisms may kick in, : “
• One is mediated by monocytes (white blood cells in the immune system that kill invaders) and TNF (tumour necrosis factor, a protein made by white blood cells), both mediators of inflammation through colony stimulating factor-1 (CSF-1, signalling pathways),”. This results in physical changes to the intestine – damage to the intestinal mucous membrane due to the inflammation.
• “The second is associated with neurotransmitter acetylcholine deficiency and dysmotility (abnormal speed of intestinal movement due to improper functioning of the muscles in the area). This is mediated through another inflammatory mediator: transforming growth factor (TGF) beta 2,”. This is the functional change in the gut.

Two disorders

• IBD is quite different from irritable bowel syndrome (IBS) that is also precipitated by stress, and seen a great deal in women. Unlike IBD though, IBS does not cause, and neither is it caused by an inflammatory response.
• IBD is caused by multiple factors, one of which is stress.
• IBD is immunologically mediated (relating to the immune system) and can be hereditary.
• Ulcerative colitis and Crohn’s disease are two examples of IBD and bear the risk of colorectal cancer, while IBS is a part of a larger clutch of disorders of the gut-brain interaction (DGBI).

Dual brains

• What the study also does is to draw attention back to the way stress impacts the body, particularly the GI system.
• There are two brains: the big brain and the small brain (nerves in the intestine).
• The gut-brain axis is controlled by the parasympathetic nervous system (the vagus nerve that regulates internal organ functions like digestion), and the sympathetic nervous system located across the body.
• Both are connected with the enteric nervous system located in the gastrointestinal system (the small brain).
• The two brains ‘talk’ to each other (exchange information), hence stress occurring in the big brain can cause changes in the small brain (butterflies in the stomach before an exam).
• Physiologically, stress affects the hypothalamus-pituitary-adrenal (HPA) axis, activates the sympathetic nervous system, releases inflammatory cytokines and cortisol. This has an impact on both IBS and IBD.

 Way forward

• We cannot eliminate stress; we can only evolve mechanisms of coping better with stress. Aerobic exercise and yoga play a big role in dissipating stress.
• Aerobic exercises release endorphins which not only boost mood, but also helps in coping better with pain. A regular yoga practice boosts brain-derived neurotrophic factor (BDNF) levels, important in learning and memory. Yoga also induces a relaxation response.