Health experts are still unsure of what exactly causes Crohn’s disease, although there are several theories on this subject. Most believe that this illness is usually caused by any (or a combination of) these factors.1
Having an Abnormal Immune System
The immune system serves as the body’s protection against infections from bacteria and viruses. However, 80 percent of your immune system is located in your gut which, in turn, is home to different types of good and bad bacteria. In a healthy person, the immune system recognizes these bacteria — it allows the good bacteria to thrive, while killing off the harmful ones.
But when something disrupts the immune system, it fails to recognize these bacteria and instead sends a special protein known as tumor necrosis factor-alpha (TNF-alpha). This protein kills all the bacteria — whether good or bad. Once this happens, white blood cells build up in the gut lining, which then triggers inflammation, ulcerations and bowel injury.2
Heredity May Lead to Crohn’s Disease
Studies confirm that genetics may indeed play a role in the development of Crohn’s disease. A study published in The American Journal of Human Genetics found that as many as 200 different genes have been identified for Crohn’s disease.3 It’s also said that having a particular genetic makeup can affect the immune system’s reaction. Certain variations in these genes may also alter the way that the immune system responds to bacteria in the gut, which can therefore lead to inflammation.4
In 2009, researchers have discovered DNA variations in a gene that can increase a person’s susceptibility to developing Crohn's disease. They pinpointed DNA sequence variants in a gene region called NLRP3, which are thought to be associated with increased susceptibility to Crohn's disease. These findings were published in the journal Nature Genetics.5
Crohn’s disease can be inherited — about 20 percent of people affected by it have a close relative who has or had this illness.6 If you have an identical twin with Crohn’s then you actually have a 70 percent chance of having it as well.7 The preliminary analysis of a 2013 study involving twins also found that identical twins are more likely to both have Crohn’s disease compared to nonidentical twins.8
Acquiring a New or Having a Previous Bacterial Infection
Some genetically susceptible individuals who had a previous infection during their childhood may actually be at risk of this illness, as the infection may trigger an abnormal immune response. Some experts also believe that certain bacteria or viruses, such as E. coli and Enteroviruses, may cause inflammation that trigger this disease.9,10
Using Certain Medications
Taking nonsteroidal anti-inflammatory medications (NSAIDs) can lead to inflammation that may trigger or worsen Crohn’s disease and other inflammatory bowel diseases.11 These include ibuprofen, naproxen and aspirin.
NSAIDs lower the levels of prostaglandins in your system. Prostaglandins are hormones that perform various functions, such as causing inflammation and pain whenever your body is injured or infected. In your gut, however, prostaglandins work by controlling your acid production and giving the mucus on your gut lining protection from stomach acids.
When you have depleted levels of prostaglandins, however, you have less protection and acid, therefore irritating and inflaming your gut.12
Smoking, a Poor Diet and Other Lifestyle Factors May Predispose You to Crohn’s Disease
Smoking is probably the most controllable cause of this chronic illness. Smokers are twice as likely to develop Crohn’s disease compared to nonsmokers, and they experience more severe symptoms that usually end up requiring surgery.13
Meanwhile, although there’s no solid evidence claiming that certain foods play a role in the development of Crohn’s disease, there are speculations saying that a diet that’s generally high in refined sugars can trigger this illness and worsen its symptoms.14 This isn’t surprising, considering that refined sugars like fructose trigger insulin and leptin resistance, which are hallmark symptoms of inflammation.
Processed foods, particularly those loaded with emulsifiers, may play a role in the development of Crohn’s disease. Scientists found that these food additives may break down the mucosal lining of your gut, increasing your risk of this illness.15
Other lifestyle factors, such as increased exposure to germ-free environments, may also play a factor in the development of this disease. One theory, called the hygiene hypothesis, suggests that children who grow up in increasingly germ-free environments may have immune systems that are not fully developed.16