Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a commonly diagnosed gastrointestinal (GI) disease that results in uncomfortable abdominal pain in the absence of any other underlying conditions such as coeliac disease or intolerances.¹

Symptoms

1. Abdominal pain and discomfort that is solved by moving of bowels and worsened by constipation – including cramps
2. Change in bowel behaviours, often resulting in diarrhoea and/or constipation. This results in urgent feelings of wanting to move one’s bowels or feeling that you haven’t finished
3. 3 different categories:
   • BS-M – Mixed movement
   • IBS-D – Diarrhoea
   • IBS-C – Constipation
4. Bloating and swelling in the abdominal area
5. Flatulence¹

Anxiety can worsen IBS symptoms.² If medical attention is sought in time then there are usually no additional health risks but If these symptoms prolong without medical attention, there may be weight loss, bleeding out of the rectum, and formation of lumps on the stomach.¹

Diagnosis

As mentioned, IBS occurs in the absence of other conditions, such as coeliac disease and inflammatory bowel disease. There are also possibilities that it is a result of an infection or an allergy/intolerance. Tests are taken to rule out other conditions that cause issues with the GI system. Predictive testing should be undertaken to determine IBS diagnosis in the absence of any concerning features.^3,4

You should only change your diet if advised to. Dietary restrictions such as lactose intolerance, large caffeine intakes, or alcohol may be affecting your digestive system.

Causes

Environmental

• Early life stress
• Food intolerance
• Antibiotics
• Enteric infection¹

Host factors

• Altered pain perception
• Dysbiosis
• Increased intestinal permeability
• Increased gut mucosal immune activation
• Visceral hypersensitivity
• Altered brain-gut interaction

Issues with motility, visceral sensation (pain perception within the viscera), and psychosocial factors (such as anxiety or early life stress) play major roles in the development of IBS.^1,2

The microbiome environment in the intestines also plays a role in IBS, along with altered gut immune activation.⁵ One treatment for IBS-D patients is Rifaximin, a broad-spectrum antibiotic. As an effective treatment, it suggests that bacterial overgrowth is a factor in IBS that disrupts the colonic microbiome environment.⁶

Autism spectrum disorder

Autism Spectrum Disorder (ASD) is a neurological developmental disorder that affects several areas of the brain, typically involving areas associated with socialisation, communication, behaviours, and learning.

ASD is typically caused by factors affecting synaptic growth and communication during normal development and increased or decreased synaptic growth in areas of the brain results in changes in behaviour and function that cause typical ASD symptoms.⁷

IBS and ASD

ASD individuals are four times as likely to have GI problems than neurotypical people, most commonly presenting diarrhoea and constipation.⁹

These issues present different behaviours in ASD such as worsened behavioural symptoms along with increased cortisol, stress and anxiety which can all contribute to worsening symptoms.⁸

Microbiome-gut-brain axis

The gut-brain axis (GBA) is a bidirectional communication between the cognitive centres in the brain and the peripheral intestinal functions.¹⁰ These interactions are influenced by gut microbiota.⁵

Dysfunction of GBA communication in ASD is seen to cause a difference in the microbiomes of the GI system. There is a marked difference in the intestinal microbiome between ASD and neurotypical people, ASD people are more often affected by motility issues, gut bacteria and dietary restrictions.⁸

ASD people have more self-restrictive diets than others⁸, often referred to as ‘safe foods’, they have foods which they tend to restrict themselves from eating and tend to dislike more food and have stronger reactions to food they dislike.⁷ A restrictive diet can cause GI problems affecting gut microbiota.⁸

Clostridium, a species of commensal bacteria within our gut, is responsible for the fermentation of carbohydrates, also attenuating inflammation and allergic diseases. Within ASD differences in Clostridium are a major factor in producing ASD-like behaviours.^8,11

Microbiota changes in ASD had lower mRNA levels for genes associated with carbohydrate digestion¹², multiple reports showing that decreasing carbohydrate consumption can improve both behavioural and GI issues, more specifically decreasing flatulence, diarrhoea, gut bloating and abdominal pain.¹³

Furthermore, ~1/3 of ASD people have higher levels of blood serotonin.¹⁴ ASD children with higher levels of blood serotonin often have GI problems. Bidirectional communication of serotonin in the GBA may cause certain IBS issues – certain gut bacteria produce serotonin, increases in serotonin levels impact gut microbiota composition, specific bacteria sense serotonin levels and has effects on its colonisation and host physiology.⁸ In experiments attempting to replicate the microbiome of ASD individuals in mice, the mice showed similar base ASD behaviours.¹⁵

Gut dysfunction can also allow the passing of proinflammatory mediators and hormones into circulation where they will eventually affect the brain’s development and function.⁸

Changes in the intestinal microbiome can affect the GBA, resulting in changes in the gut and brain. The health of the gastrointestinal system impacts brain development in a major way, affecting emotional and social brain development during the paediatric years.⁸

Anxiety and early stressors

ASD individuals have a higher rate of comorbidities with mental health disorders such as anxiety, and as stated before, increased anxiety level can promote IBS symptoms.^2,9

Issues with IBS can also increase stress factors that also affect IBS in ASD individuals.⁸

ASD people also more commonly have early life stressors, an environmental factor of IBS. This is due to the stigmatisation or bullying that occurs in early life, along with increased stress due to difficulties an ASD child goes through.¹⁶

Treatment for IBS in ASD individuals

A common treatment throughout testing and for IBS is dietary restrictions, either preventing the issue or improving intake of naturally occurring substances.¹

ASD individuals’ restricted diets can make IBS treatment difficult. Refusal to change may result in self-starvation. Diet restrictions and inability to change their diet means that treatment for IBS through different foods is sometimes minimal.⁷

FODMAPs are a group of foods that have short-chain highly fermentable carbohydrates which can increase IBS-D symptoms due to their fermenting nature. These foods include fruit and vegetables, wheat products, sorbitol, and some dairy products. Increasing/decreasing intake of these foods – while still maintaining healthy eating especially with fruits and vegetables – can alleviate some of the symptoms.¹ However, if some of these foods are key factors in an ASD person’s safe foods it is difficult to reduce.

There are medicinal ways to alleviate IBS symptoms. Although changing dietary intake is recommended this provides an alternative option for those who may not have that option or more severe symptoms. Treatment of IBS is symptom led, focusing on alleviating the symptoms that are most persistent or detrimental, often alleviating the change in bowel movements.¹

Constipation

Exercise can increase colonic movement due to the increased need for energy and supply to different areas of the body. This alleviates constipation symptoms and allows for normal bypass.¹⁷ ASD individuals with a common need for rigid schedules may be difficult to organise and often must become a part of their routine.

Medicinally synthesised and natural laxatives are a common way to prevent constipation and are safe to use in the correct amounts, Laxatives can be bought in drug stores, natural laxatives are particularly rich in fibre:¹⁸

• Chia seeds
• Berries
• Legumes
• Coffee¹ and more

Natural laxatives are much safer than synthetic laxatives and can contribute well to your diet.

Additionally, drinking enough water helps prevent constipation.¹⁹

Diarrhoea

Diarrhoea is most often treated medically, typically with drugs like loperamide and probiotics.¹ Diarrhoea can also be treated through changes in your diet:

• Probiotics are naturally found in (or added to) many fermented foods like FODMAPs¹
• The BRAT diet²⁰, aka the bland diet

A gluten-free or low-carbohydrate diet may be beneficial, particularly for ASD individuals.¹³

As mentioned before, in some cases the antibiotic rifaximin helps to prevent abdominal pain and diarrhoea.⁶

Antidepressants

Patients who experience constant/chronic abdominal symptoms can have a positive response to low doses of certain antidepressant medications – TCAs and SSRIs.²¹

Due to the higher prevalence of depression in ASD individuals they may already be taking an antidepressant and could present both positive effects in their mental health and IBS.⁹

Summary

IBS in ASD individuals has a high comorbidity, this is due to the microbiome changes seen in the GI system. The changes elicited result in changes within the GI system that cause IBS, often correlating towards not being able to digest carbohydrates properly, and changes within the brain that cause the social and communication symptoms present within ASD.

While there are these seen changes in ASD populations, it is not the only cause. IBS is caused by multiple different host and environmental factors which other ASD people may be subject to without the changes in the GBA. Anxiety is a factor that affects a large portion of ASD populations, dietary restrictions self-imposed by the person, and various life stressors and differences in pain perception are all factors that contribute to IBS, even without issues with microbial environments.

Treatment of IBS in ASD people can be more difficult than usual due to their restrictive diet. Incorporating new foods is difficult, but there are medications and methods to try if these do not work out.