Ulcerative Colitis: Causes and Risk Factors

Show Article Table of Contents

The exact causes of ulcerative colitis (the inflammatory bowel diseases (IBD)) is not known, but there are several theories. Ultimately, scientists believe that there is more than one cause and that the several different factors work together to cause the disease. Further, the cause for one particular individual with the disease could be different from another’s.

Factors thought to cause ulcerative colitis include a complex interaction of genetics, immune response, and environmental triggers.

ulcerative colitis causes and risk factors
© Verywell, 2018

Genetics

Although ulcerative colitis is known to “run in families,” researchers note that it was not as simple as being passed down from parent to child. More than 100 genes have been identified as having a potential role. However, most people do not have a family member who also has the disease—only about 10 and 25 percent of those who have ulcerative colitis also have a close relative who has a form of IBD.

The most important risk factor currently identified for developing IBD is having a relative who also has the disease. Yet having the genes that are associated with ulcerative colitis does not always mean a person will develop the disease. There’s another piece to the puzzle, and researchers think that this is where a variety of other potential triggers come into play.

Autoimmune Reaction

Another factor thought to be a part of the development of IBD is an immune reaction. For this reason, ulcerative colitis is currently thought to be an autoimmune, or an immune-mediated, condition.

The idea is that the immune system is triggered by something (a bacteria or a virus are some of the examples) and it begins working as it should to protect the body from a foreign invader. Something goes wrong, however, and the immune system doesn’t stop there but continues to target other parts of the body.

In the case of ulcerative colitis, that is the large intestine. This is the theory behind medications that suppress the immune system and why they are effective in some cases of IBD; when the immune response is lowered, the disease becomes less active.

Environmental Triggers

Genetics and the immune system response may not be enough to explain the development of ulcerative colitis. There may be one or more conditions in the environment, too.

It’s not currently known how or if triggers work together or interact with the other potential causes of ulcerative colitis, but it is thought that more than one is probably involved. A few potential candidates include:

Smoking

Ulcerative colitis is sometimes called a “disease of non-smokers.” The disease is more common among those who have quit smoking. It’s not recommended that people begin smoking cigarettes or go back to smoking after being diagnosed with ulcerative colitis. The effect that smoking has on the body far outweighs any possible benefit it might have for ulcerative colitis.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

This type of pain medication is often used with care in people with ulcerative colitis because it has been shown to be associated with flare-ups of the disease. Even in people who don’t have ulcerative colitis, NSAIDs has the potential to cause irritation and bleeding in the digestive tract.

Antibiotics

Antibiotics have been shown to precipitate flare-ups of the disease for some people. Some research has shown that antibiotics, especially when taken for a long period (such as 30 days) of time or used in young people, is associated with a higher risk of developing a form of IBD.

Contraceptive Pill

It’s not known if the use of the contraceptive pill (birth control pill) may be a risk factor for developing ulcerative colitis, as the evidence is conflicting. There is more evidence that there is an association with Crohn’s disease. 

Geographic Location

Ulcerative colitis tends to occur in people who live in northern climates and in cities. However, the rate at which IBD is being diagnosed is increasing around the world, particularly in areas that are becoming more developed. 

Common Myths

There are many misconceptions about what can cause ulcerative colitis, especially because some early research pointed at stress, mental illness, and diet as being potential triggers. It’s now known, however, that ulcerative colitis is not caused by having stress or from eating the wrong food. Stress and diet can certainly impact the symptoms of ulcerative colitis, and diet alterations and stress reduction can be treatments, but they are not causes.

How Ulcerative Colitis Is Diagnosed
Was this page helpful?
Article Sources
  • Aniwan S, Tremaine WJ, Raffals LE, et al. "Antibiotic Use and New-Onset Inflammatory Bowel Disease in Olmsted County, Minnesota: A Population-Based Case-Control Study.” J Crohns Colitis. 2018 Jan 24;12:137-144. doi: 10.1093/ecco-jcc/jjx135
  • Jantchou P, Monnet E, Carbonnel F. "Environmental risk factors in Crohn's disease and ulcerative colitis (excluding tobacco and appendicectomy).” Gastroenterol Clin Biol. 2006 Jun-Jul;30:859-867.
  • Kornbluth A, Sachar DB; Practice Parameters Committee of the American College of Gastroenterology. "Ulcerative colitis practice guidelines in adults: American College Of Gastroenterology, Practice Parameters Committee.” Am J Gastroenterol. 2010 Mar;105:501-23; quiz 524. doi: 10.1038/ajg.2009.727