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Digestive Disorders > IBD > Crohn's Disease

Crohn's Disease Causes: A Guide to Triggers

Laura Fouquette

Laura Fouquette

There are various theories about the causes of Crohn's disease. It can occur in individuals with a genetic predisposition who are exposed to one or more environmental factors. The immune system then becomes dysregulated and produces an excessive inflammatory response.

Not all scientific explanations for Crohn’s triggers are equally accepted, and some are supported by more evidence than others due to the quality and number of studies.

Is Crohn's disease genetic?

Even if the exact cause of Crohn's is unknown, it is believed that genetic factors play a role. The single most important factor for developing an inflammatory bowel disease (IBD), such as Crohn's disease, is having a family member with IBD. The IBD risk is:

  • 30% if both parents have IBD
  • 10% if one parent has IBD
  • 5% if one sibling has IBD

Although there is no single gene that causes Crohn's disease, several genes are known to strongly contribute. Because not everyone with these genes develops the disease, it is believed that Crohn's is a result of the interaction between genes and the environment.

Does smoking cause Crohn's disease?

Cigarette smoking can trigger Crohn’s flare-ups and is the single most important determinant of Crohn's disease risk. It not only increases disease risk but also worsens disease severity and complications. Smoking also increases the likelihood of treatment failure, as smoking damages intestinal flora, the intestinal wall, and signaling pathways.

Smoking cessation reduces flare-ups and the need for medication by causing increased diversity of gut microbiota. In the treatment with Crohn's disease, doctors will suggest smoking cessation as the initial treatment for smokers.

Can bacteria and viruses trigger Crohn's disease?

Studies have demonstrated that childhood gastrointestinal infections and mumps increase the risk of Crohn's disease. Other studies have shown that IBD is common in areas with contaminated lakes, rivers, or drinking water. There is a discussion about whether Crohn's could also be triggered by pathogens in water transmitted from animals to humans; this could explain its frequent occurrences in certain places.

Do vaccines or antibiotics trigger Crohn's disease?

Vaccines do not increase the risk of Crohn's disease.

Antibiotics are known to alter the intestinal microbiota. A large Finnish study of children demonstrated an association between Crohn's disease and antibiotic use, especially among boys and with a particular class of antibiotics (cephalosporins). Other studies have confirmed antibiotics as a risk factor for new-onset Crohn's, most notably among children.

Painkillers, birth control, and Crohn's disease

Crohn's disease is more common among those with a history of taking nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen.

There is an association between oral contraceptive use and Crohn's disease: A British twin study found a four-fold increase in risk.

A large study of women found that postmenopausal estrogen therapy does not increase the risk of Crohn's disease.

The hygiene hypothesis: C-sections, breastfeeding, clean houses, and Crohn’s

Among scientists, the hygiene hypothesis is controversial and is not considered important when discussing Crohn's disease risk. According to the hypothesis, some develop disease because they were not exposed to sufficient bacteria and germs as children. The theory claims that intestinal flora can be damaged if the baby is born via C-section, does not drink breast milk, or lives in a household that is too clean.

Studies have previously described the benefits of breastfeeding or vaginal birth to supplement the baby's prenatal gut microbiota with that of the mother. Recent studies have found no association between breastfeeding and IBD in adulthood.

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Exercise and Crohn's disease

Exercise is known to decrease inflammation, lower stress levels, and improve quality of life. A large study of American women showed that exercise reduces the risk of Crohn's disease by 44%. Current research also suggests that low-intensity exercise does not cause flare-ups or worsen IBD symptoms. More studies are necessary to make general recommendations.

Sleep and Crohn's disease

Disturbed sleep is generally associated with poor health, and lack of sleep can affect immune function and increase inflammation. Those with Crohn’s and disturbed sleep experience fewer symptom-free remission phases, compared to those with Crohn's and normal sleep. It is important to pay attention to sleep habits, and doctors treating sleep disorders may improve Crohn's outcomes.

Mental health, stress, and Crohn's disease

It is common to experience stress or mental health conditions alongside long-term illness, including IBD. People diagnosed with Crohn's are more likely to have depression or anxiety than the general population.

Short-term stress also increases the risk of flare-ups. These experiences can release stress hormones and increase intestinal inflammation. When inflammation increases, stress or symptoms of mental health conditions can also increase, starting a vicious cycle. More research is needed into the mechanisms of the nervous system and gastrointestinal function.

If coping with Crohn's disease is emotionally overwhelming, contact a psychotherapist, and add to your existing Crohn’s treatment plan.

Can an unhealthy diet cause Crohn's disease?

An unhealthy, westernized diet full of fat and refined carbohydrates can significantly change the intestinal flora and contribute to IBD development. In a study of children, daily fast food and high sugar consumption were associated with earlier IBD onset.

Several studies have compared the pre-onset eating habits of adults with Crohn's disease to that of healthy people. Healthy study participants ate:


  • Sugar
  • Meat
  • Fat


  • Vegetables
  • Dietary fiber
  • Vitamins

The relationship between Crohn’s disease and diet is complex.

Does the sun protect against Crohn's disease?

IBD is most common in Canada and Northern Europe. Scientists explain this north-south divide by vitamin D production: The more sun exposure, the higher the blood vitamin D level. In mouse models, insufficient vitamin D influences disease development, yet it is still unclear whether this applies to humans.

Summary of Crohn’s disease risk factors

  • Having a family member with IBD
  • Smoking
  • Infections (childhood gastrointestinal infections, mumps, exposure to contaminated water)
  • Antibiotics in boys, such as cephalosporins
  • NSAIDs, such as ibuprofen
  • Oral contraceptives
  • Physical inactivity in women
  • Depression and stress
  • Unhealthy high-fat diet, full of refined carbohydrates

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Laura Fouquette

Laura Fouquette

Laura Fouquette is a digital health enthusiast from California. She completed a Master of Public Health (MPH) in Epidemiology/Biostatistics and a Bachelor's of Public Health at the University of California, Berkeley. She currently works as a freelance writer/researcher in Berlin.

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