Ulcerative colitis (UC) appears to run in families, suggesting that genetic factors may play a role. In addition, scientists have identified changes in a number of genes that may contribute to the development of UC.

However, experts are still working to determine the precise role that specific genes play, if any.

While the exact cause of UC for each person is unknown, researchers believe that it results from an abnormal immune response or changes in the protective barrier of the intestine.

There is also a complex interplay of genetic susceptibility and environmental triggers. These factors may make a person more likely to develop an inappropriate immune response, which can result in inflammatory bowel disease (IBD) such as UC or Crohn’s disease.

This article discusses the genetic factors linked with UC, as well as other triggers that may set off the disease.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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UC is a long-term condition affecting the gastrointestinal tract.

It is a form of IBD and an autoimmune condition. A fault in the immune system may cause the body to mistakenly attackTrusted Source healthy cells and fight nonexistent viral or bacterial infections, leading to chronic inflammation of the inner surface of the colon. As a result of this inflammation, ulcers (sores) develop in the intestines.

SymptomsTrusted Source vary from person to person but generally include:

People with UC will have periods of active disease, which are known as flares, and periods of remission, during which they may not experience any symptoms.

IBD resources

Visit our dedicated hub for more research-backed information and in-depth resources on inflammatory bowel disease (IBD).

Genetic variations that contribute to changes in the protective function of the intestinal lining may be connected to the development of UC. They may also contribute to unusual immune responses to typical bacteria in the digestive tract.

Researchers have identified 242 susceptibility lociTrusted Source (DNA sequences) for IBD. They have associated 50 of these with very early onset inflammatory disease. The authors of a 2019 study also found six genes responsible for the progression of UC.

According to a 2021 study, UC has some genetic similarities to multiple sclerosis, another autoimmune-mediated disease.

The following sections discuss other factors that link genetics to an increased susceptibility to UC.

Family history

According to a 2017 review, people who have a first-degree relative with UC — such as a parent or sibling — have an increased risk of experiencing UC themselves.

The authors state that 8% to 12% of people with IBD report a positive family history, but they conclude that Crohn’s disease may show a more frequent familial pattern than UC.

The review also describes a cumulative effect, with the highest incidence reported in families in which the disease affects three or more family members.

Twin studies

Because identical twins have the same genetic material, twin studies can help researchers understand which traits are due to genes and which are the result of environmental factors.

Among identical twins, the risk of Crohn’s is significantly higherTrusted Source than the risk of UC. In non-identical twins, the rates are lower for both forms of IBD.

Additionally, children have a higher risk of developing IBD if both of their parents have it.

Ethnicity

The frequency of UC is much higher in certain ethnic groups.

A 2018 study suggests that the Ashkenazi Jewish population has a fourfold greater riskTrusted Source of IBD. The researchers considered someone to have a higher risk of IBD if a first-degree, second-degree, or more distant relative had a diagnosis of Crohn’s or UC.

IBD is also more common in white people than in people of African and Asian descent.

However, the authors of a 2018 review noted a higher incidence of UC in people of South Asian descent who had immigrated to the United Kingdom and Canada. In this case, environmental factors may play a more significant role in determining UC than other factors.

Sex assigned at birth

Generally, IBD affects males and females equally, but males are more likely to receive a UC diagnosis at an older age.

However, the Crohn’s & Colitis Foundation of America reports that UC is more common in males than in females. In addition, males are more likely to receive a diagnosis in their fifties or sixties.

A person’s environment also seems to play a role in increasing their risk of developing UC. Other possible triggers relate to a person’s health and treatments they receive from a young age, their lifestyle, and the level of stress they experience.

Environment

A study from 2017Trusted Source suggests that people living in rural households might have a lower risk of both UC and Crohn’s than those who live in urban households.

These comparisons of a person’s environment relate to:

  • population size
  • population density
  • economic and social factors from neighboring regions

Lifestyle

Smoking has a stronger link with Crohn’s disease than with UC. However, a 2021 review found a 2.3-fold riskTrusted Source of UC in current smokers.

According to Crohn’s & Colitis UK, people who smoke may have a lower risk of developing UC, and those who have quit smoking may have a higher risk. However, research on the relationship between smoking and UC is mixed. Additionally, smoking has an overall negative effect on health, and health authorities generally recommend that people avoid smoking.

Some aspects of a person’s diet may also trigger UC. Research from 2019Trusted Source shows the effects of a Western-style diet (WSD) on a person’s likelihood of developing IBD. The authors suggest that in the long term, the amount of refined carbohydrates in a WSD may change the gut microbiota, increasing the risk of many diseases, including IBD.

The researchers also found that the fecal microbiota of people who followed the Specific Carbohydrate Diet had a higher biodiversity index than those of people who followed a WSD, meaning that the Specific Carbohydrate Diet produced a healthier gut environment.

A 2021 study also suggests that a low fat, high fiber diet may reduce inflammation markers in UC, leading to improved quality of life.

Stress

A 2016 review found a bidirectional relationshipTrusted Source between stress and depression and IBD, meaning the conditions may affect each other. Additionally, a 2022 reviewTrusted Source suggests that inflammation in the central nervous system can trigger depressive symptoms.

Experts believe that the gut-brain axis plays a crucial role in the disease progression and relapse of IBD symptoms.

Childhood experiences

According to a 2016 reviewTrusted Source, taking antibiotics in childhood and adolescence increases a person’s risk of IBD, namely Crohn’s.

Both forms of IBD may also occur in people who drank breast milk as babies because breast milk influencesTrusted Source a child’s microbiome.

Other possible childhood triggers linked to UC include:

Doctors do not routinely request genetic testing to diagnose UC in current practice.

No specific genetic tests can check for UC, especially since medical professionals associate many genetic variations with the disease.

However, genetic markers show a great potential to identify the outlook and treatment outcomes for people with IBD. A study from 2019Trusted Source found genetic variants linked with medication side effects in people with IBD.

UC is a chronic disease that may affect a person’s quality of life.

It has no known cure, but treatments can help induce remission and reduce the severity of symptoms. Most people need long-term medications and lifestyle changes to manage UC, while some may need surgery.

Researchers aim to better understand the biological processes that drive the disease to develop strategies that can help prevent its progression.

UC is a complex disease that results from both genetic and environmental factors. Certain genes can increase a person’s risk of developing the disease. If a person’s parent or sibling has UC, this increases their risk of developing it.

While UC runs in families, it can occur in anyone, even in people with no family history of the disease. Other factors can influence the development of UC, including the environment a person grows up in and aspects of their lifestyle such as stress level and diet.