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Is IBS Genetic? The Role of Genetics In IBS

By 14th August 2023IBS
Is IBS Genetic

What is IBS?

IBS is a common and chronic disorder in which sufferers experience abdominal pain or discomfort and diarrhoea and/or constipation. This impacts between 5-10% of the global population and can have a significant impact on quality of life.

This can also be associated with altered gastrointestinal motility and symptoms such as bloating, constipation/diarrhoea as well as abdominal pain. 

Many approaches are available to treat IBS which include medications, dietary modifications, gut-directed hypnotherapy as well as over-the-counter supplements such as probiotics. 

The first line medical considerations for IBS treatment can include changes to the diet, soluble fibre as well as antispasmodics drugs.

The causes of IBS can be wide-ranging and varied. This means that there is no single treatment for all patients with IBS. However, personalised treatments are available to address the specific causes in patients.

Some of these factors can relate to genes and genetics while others can be related to environmental factors and life experiences. [Source: PubMed]

What causes IBS?

While there is not a single cause for all cases of IBS, genes and genetics are one of several risk factors that can increase the risk of developing IBS. With genetics and genes increasing the chance of developing digestive issues, further factors or imbalances in the gut or body are generally needed to lead to the onset of IBS symptoms. 

One of the most common factors is when IBS symptoms develop following a form of digestive infection. This type of IBS is termed post-infectious IBS. In this situation, symptoms appear following a bacterial, viral or protozoal infection of the digestive tract. This has been reported in approximately 10% of those with IBS at the start of their symptoms.

Research indicated that in the 12 months following a digestive infection, the individual is 4 times more likely to develop IBS symptoms. 

The reason an infection can lead to IBS symptoms is understood to be due to:

  • a low-grade inflammatory response
  • immune activation in the gut
  • imbalances in the gut microbiome

There are further risk factors that may contribute to the development of post-infectious IBS.

These include:

  • being female
  • exposure to antibiotics
  • psychological distress preceding the illness
  • the severity of the infection 

In further research into post-infectious IBS, it was found that 8 years later, 15% of patients continued to experience symptoms. [Source: PubMed]

Other factors that can increase the risk of developing IBS include:

  • altered gut motility
  • changes to the gut-brain axis
  • early life stress
  • ongoing stress
  • visceral hypersensitivity
  • poor sleep
  • food intolerance
  • medications [Source: MDPI]

How is IBS diagnosed?

The diagnostic route many people follow is that conditions such as inflammatory bowel disease and cancer have been excluded. 

However, with the cause of symptoms unknown the diagnosis of IBS can often be given when altered bowel patterns are accompanied by pain that improves along with defecation.  This is outlined in the Rome Criteria. [Source: PubMed

Three main subtypes of IBS are recognized as:

  • Constipation-predominant (IBS-C)
  • Diarrhoea-predominant (IBS-D)
  • Mixed/alternating constipation and diarrhoea (IBS-M) [Source: Nature]

Who is more likely to get IBS?

One reason why IBS is challenging to address is that there are many risk factors. 

IBS is associated with changes in several areas.

These include:

  • A change in central pain processing
  • Increased gut permeability
  • Mast cell activation
  • Disordered motility
  • Dysbiosis [Source: BMJ]

Additionally, up to 1 in 10 cases of IBS are triggered after infection. This is termed postinfectious IBS (PI-IBS).  This involves changes to the bacterial balance, functioning of the gut lining as well as a low level of inflammation following an infection. [Source: PubMed

Other risk factors for IBS include:

  • Genetics and genes
  • Age. Those with IBS are more likely to be under 50.
  • Sex. IBS is more common among women.
  • Family history of IBS.
  • Emotional aspects such as anxiety, depression or other mental health issues. This can also include a history of sexual, physical or emotional abuse. [Source: Mayo Clinic]

Genetics and IBS

Someone is more likely to develop IBS if a relative also has the condition.  This increases the risk by 2-3 times.  This means that if 1 member of the family has symptoms of IBS there is a 1 in 3 chance of another member of the family having similar symptoms. [Source: Mayo Clinic]

One study indicated that those with a stronger family history of IBS had:

  • more severe pain
  • fibromyalgia
  • heartburn
  • asthma
  • reported symptoms of loose stools
  • urgency
  • constipation [Source: PubMed]

This research also indicated that the age at which symptoms began was not determined by a family history of IBS.

Further studies into monozygotic twins (who are genetically identical) examining rates of IBS.  This concluded that genetics may play a role in up to 20% of IBS cases, indicating that genes do not play a considerable role in the development of IBS symptoms. [Source: PubMed

Do genes cause IBS?

Specific genes and genetics have been associated with and linked to an increased risk of developing IBS and gut issues. While these do not cause IBS in all of those with these genes, having these genetics may increase the risk if other elements are also present. For example, certain genes may increase the risk of developing post-infectious IBS following an infection.

Certain genes and genetics have been researched and associated with various aspects of digestive health and gut function.

For example, certain genes have been associated with variations in the genes that produce digestive enzymes, specifically the surcease-isomaltase gene.

Other genes such as the SCN5A gene have also been researched. This has been found to be mutated in 2% of those with IBS. This gene supports the function of the muscles within the gut, therefore if this gene is mutated, the muscles within the digestive tract may not function effectively leading to symptoms of IBS.

It’s been reported that monozygotic twins have a higher rate of IBS which does indicate a genetic component also. However, having a parent with IBS is also a strong predictor. This does suggest that while genetics can play a role and increase the risk of IBS, environmental factors may be more important than genes and genetics. [Source: PubMed]

Environmental Factors and IBS

Genetic studies can be difficult when examining families that live in the same environment.  The reason is that those living in the same household can be exposed to the same non-genetic risk factors for developing symptoms of IBS.

This can mean that if several members of the same household experience symptoms it can be unclear whether or not is it due to genetics or the environment.

Shared environmental exposures between multiple family members include:

  • verbal abuse
  • physical abuse
  • sexual abuse
  • quality of food intake
  • shared household stressor/s (e.g. ill family member, unemployment etc.)
  • parenting style
  • learned illness behaviour

Abuse (verbal, physical, or sexual) has been indicated to be more common in those with IBS with up to 50% of IBS sufferers reporting one of these factors. This indicates that a possible reason for IBS symptoms developing is psychological based rather than gastrointestinal (e.g., a change in motor or sensory function in the gut). [Source: PubMed

In balance to this, another study that was carried out at a population level indicated that even though adverse events experienced during childhood were associated with IBS. These psychologically distressing events were not seen as risk factors for IBS when symptoms of neuroticism (the trait disposition to experience negative effects, including anger, anxiety, self‐consciousness, irritability, emotional instability, and depression) were taken into consideration.

Most significantly, as most patients with IBS did not experience abuse during childhood abuse is not a requirement for the development of these symptoms. [Source: PubMed

One way that humans develop is by modelling the behaviour of those around them. This is termed a learned behaviour.  In specific relationship to IBS, this can be termed learned illness behaviour. 

A study indicated that those with symptoms of IBS displayed somatic behaviours. Such as visiting a doctor more often and for what was considered ‘minor complaints’ and interestingly reported being given gifts or special foods during illness.  These were seen to be factors that reinforced or rewarded the symptoms. [Source: PubMed

A similar study also reported that as children, those who would later go on to develop IBS symptoms would have more days off school indicating their parents may have paid greater attention to their complaints potentially reinforcing chronic illness behaviours. [Source: PubMed

While adverse experiences and learned illness behaviours may explain a subset of patients that develop IBS. The role they plan in the family clustering of symptoms is still being explored.

Genes and IBS

Approximately 60 genes have been explored to connect the dots between our DNA and the development of IBS.  These genes studied have been indicated to play a role in the following pathways:

  • Serotonin
  • Adrenergic
  • Inflammation
  • Intestinal barrier
  • Psychiatric


This is due to 2 of the potential factors that contribute to IBS symptoms being an alteration in motor function in the gut as well as a potential change in how the bacterial balance is regulated. [Source: PubMed]

Is IBS more common in women?

While it is related to genes and genetics, the individual’s sex has a role to play in digestive issues such as IBS.

Researchers have repeatedly found that women are at an increased risk of developing IBS and gut issues. This can be seen with women at 1.5 to 3 times the risk of developing IBS when compared to me.

When researched on a populational level, 14% of women have IBS when compared to 8.9% of men.

However, when this is researched in non-western countries the rate of IBS between men and women is closer in level. For example, in South Asia, South America and Africa.

Researchers theorise this more even balance between men and women may relate to access to health care as well as symptom normalisation, which refers to men feeling more open to discussing these symptoms and seeking medical help. [Source: PubMed]

At what age does IBS usually begin?

As well as genetics and genes, researchers have examined IBS and how it relates to age. Specifically, if there is a certain age group that is more likely to develop gut symptoms such as IBS.

Part of this research also examined the different subtypes of IBS (for example, if someone is experiencing constipation or diarrhoea) and if this was more prevalent depending on the age of the patient. This research concluded that age did not predict the subtype of IBS.

It was reported during these studies that approximately 50% of patients with IBS indicated that their first symptoms of IBS started before the age of 35 years old. 

Additionally, the rate of IBS is lower in those over the age of 50 years old. Specifically, the rate of IBS is 25% lower in those aged 50 or over when compared to those under 50 years old. [Source: PubMed]

This indicated that symptoms of IBS can naturally improve as the patient ages. This is averse to the concept that IBS can be a chronic life-long condition. If this were true, the rates of IBS would remain the same across all age groups. Importantly this is not taking factors such as genes or genetics into consideration. 

There has been further discussion and research around IBS and how it related to age. For example, even though IBS patients who are aged 50 and over reported milder pain, they also report a worse quality of life. This indicated that even though symptoms are lower the impact they are having is higher.

Additionally, age has also been reported to be a factor in how long it takes someone to seek medical help. For IBS patients over the age of 65, on average they have been experiencing symptoms of over 12 months before seeking medical help. While for those under this age, a shorter duration of symptoms is experienced before they seek support. [Source: PubMed]

Genes, genetics and gut health

There are many digestive diseases and gut health issues that have similar symptoms. These are symptoms such as digestive discomfort, bloating, changes in bowel patterns and food intolerances.

These are diseases such as:

  • Ulcerative colitis
  • Crohn’s disease
  • Coeliac disease

It is well understood that these gut conditions have a genetic aspect to their onset. It is not always the case that these gut conditions are ruled out prior to studies based on families. Therefore, it can be possible for another genetic disorder to mimic IBS.

On balance to this, research has been carried out on these genetic conditions and how they appear with symptoms of IBS. For example, Coeliac disease was found to be present in 1% of a sample population of IBS patients. This was a similar percentage to a sample of the general population without IBS symptoms.

Additionally, genetic research into Crohn’s disease, Ulcerative colitis and IBS found that the genes that can increase the risk of inflammatory bowel diseases were not found in those with IBS. This indicates that there are separate sets of genes that increase the risk of developing each condition. 

A genetic link has also been reported between IBS and non-digestive conditions such as psychiatric conditions. For example, conditions such as depression have been found in higher rates in those with IBS with medications often used to treat depression showing benefit in IBS. [Source: PubMed]

Lactose, food intolerances and genetics

Food intolerances and reactions can be due to changes in the gut microbiome (such as SIBO) but are also related to genetics and genes. One food component, in particular, is lactose.

Lactose is a carbohydrate that is naturally present in milk. For this to be digestive it has to be broken down into glucose and galactose and then absorbed along the lining of the small intestine. In humans, this process is governed by the enzyme lactase-phlorizin hydrolase (LPH).

LPH is solely located in the small intestine and is most active during the nursing period (eg breastfeeding). However, following weening, the levels of this enzyme reduce in the majority of humans which is referred to as lactase non-persistence. It is estimated that approximately 66% of humans worldwide are lactase non-persistent. This means that when lactose-containing foods are consumed digestive symptoms can result.

In those with the ongoing production of this enzyme, it is referred to as lactase-persistence. This is common among those who descend from those who practice cattle domestication and therefore relied on dairy as an important source of food and calories.

This genetic compound is understood to be related to the genetic alterations that lead to the ongoing production of the enzymes required for lactose digestion.

The regions with the highest rates of lactose persistence are across northern Europe. These levels however decreased across the middle east region with lower levels still in Africa and Asia. [Source: PubMed

Are you born with IBS or does it develop?

It is rare for IBS to be present from birth and it more often develops over a period of time. This can be because as humans progress in age they come into contact with more factors that have the potential to impact the balance of the gut and the digestive tract. 

However, genes and genetics may increase the risk of developing IBS and gut issues. 

Studies have also reported specific events during early life that may increase the risk of developing IBS. 

This can be in infants:

  • exposed to gastric suction during the neonatal period
  • born to mothers with gestational diabetes and pregnancy-induced hypertension
  • admitted to a special care baby unit
  • having an umbilical hernia
  • having pyloric stenosis
  • with a history of cow’s milk allergy [Source: PubMed]

There are also other factors that can influence digestive function and increase the risk of developing IBS. 

These include:

  • genes and genetics
  • early life stress
  • ongoing life stress
  • low-grade inflammation
  • food sensitivities 
  • immune activation in the gut
  • decreased coping
  • changes in the gut microbiome [Source: PubMed]


While certain genes have been indicated to play a role in the development of gut issues a single gene being the cause of IBS is unlikely to be found.  Rather than there being a single cause of IBS, genetics may simply be seen as another risk factor.

Additionally, we are unable to alter our genetics.  This means that the modifiable factors (eg the areas we have a degree of ability to control and alter) are central to improving digestive issues. 

These include dietary patterns, levels of stress and the quality of sleep as all factors that we can support alongside addressing key imbalances in the gut microbiome.

Working with a gut health practitioner can guide the process to get to the underlying cause of gut symptoms.