Researchers believe that ulcerative colitis is caused by a combination of genetic and environmental factors that trigger an abnormal immune reaction. However, the exact cause isn’t known.

Ulcerative colitis (UC) is an autoimmune disorder that affects more than 1 in 250 people in North America. As with other autoimmune disorders, symptoms develop due to your immune system accidentally attacking healthy cells.

If you have UC, you can develop ulcers and inflammation in the lining of your colon that can cause bloody diarrhea and other gastrointestinal symptoms that can range from mild to severe. While the exact cause of UC isn’t known, a family history of the condition is one of the biggest risk factors for developing it.

Keep reading to learn more about these risk factors and potential causes of UC.

The exact cause of UC is not clear, but genetics and environmental factors likely both play a role. UC falls into a group of conditions called immune-mediated inflammatory disease, meaning it’s characterized by inflammation caused by damage from your immune system.

Factors researchers think may play a role include:

  • defects in the epithelial barrier, or surface, of your colon
  • excess build-up of immune cells called leukocytes
  • disruptions in your gut microbiome

Genetics

A family history is the strongest risk factor for UC.

Roughly 8% to 14% of people with UC have a family history, and people with a parent or sibling with UC seem to have a risk about four times higher of developing it, too.

Ethnicity

Jewish populations seem to have a higher risk of UC than other populations.

UC is one of two main types of inflammatory bowel disease (IBD), along with Crohn’s disease. Researchers often report statistics for these two conditions together.

In the United States, the prevalence of IBD among adults and children is estimated at:

  • Non-Hispanic white: 0.8%
  • Black: 0.5%
  • Hispanic: 0.5%
  • Asian Americans: 0.4%

Age

People most commonly receive a UC diagnosis between the ages of 15 and 30, but doctors also frequently diagnose it in people between 50 and 70.

Disruptions in gut microbiome and immune system dysfunction

Scientists have theorized that disruptions in the microbiome of your gut could play a role in the development of UC, but this is still under investigation. Researchers have identified differences in the microbiomes of people with and without UC.

Some researchers believe that a misdirected immune response against harmless bacteria in the gut may trigger inflammation.

Stress and anxiety

Stress seems to be one top risk factor for UC flare-ups. Although stress doesn’t cause UC, it may contribute to periods of worsening symptoms.

Other environmental triggers

Other commonly reported triggers for UC flare-ups include:

Lifestyle habits

According to the Centers for Disease Control and Prevention (CDC), people with IBD are more likely to:

  • have formerly smoked
  • sleep fewer than 7 hours per day
  • fall short of recommended physical activity guidelines
  • have experienced serious psychological distress
  • have other chronic health conditions

Dietary risk factors

Dietary risk factors that have been linked to a higher risk of UC include lower intakes of:

Some dietary patterns have also been linked to better outcomes in people with UC. These include:

The main symptom of UC is bloody diarrhea that may also contain mucus. Other symptoms may include:

It’s a good idea to seek medical attention if you develop persistent symptoms like bloody stools, abdominal pain, or an unusually frequent urge to use the bathroom.

Your doctor may refer you to a specialist called a gastroenterologist if they suspect UC or another gastrointestinal condition.

A gastroenterologist can confirm the diagnosis through tests like a colonoscopy. Regular follow-up appointments with a gastroenterologist help monitor the condition, adjust treatment, and prevent complications over time.

Stress doesn’t cause UC, but it’s thought to be a trigger for many people. Some experience flare-ups of symptoms during high-stress periods.

UC likely isn’t completely preventable since genetics likely play a role in its development. Making healthy lifestyle choices like eating a balanced diet and avoiding your triggers may help reduce symptoms.

Colitis is the medical term for swelling in your large intestines. It has many causes like infections, medications, or autoimmune conditions like UC. UC specifically refers to an autoimmune disease that causes colitis and the formation of ulcers inside your colon.

Many people with UC are able to live typical lives and manage their symptoms by avoiding their triggers. Disease severity can vary between people, but your healthcare professional can help you develop the best treatment plan to minimize your symptoms.

The exact cause of UC isn’t clear, but researchers think it is an autoimmune disease caused by a combination of genetics and environmental factors. Many people experience flare-ups in symptoms when exposed to triggers like stress or certain foods.

Minimizing exposure to your triggers may help you reduce active flare-ups. Working with your healthcare professional can help you manage your symptoms.