Irritable bowel syndrome (IBS) and chronic fatigue syndrome (CFS) frequently coexist. Separately, each presents challenges, and together they can be a double whammy to your quality of life.

Studies indicate that many things may lead to the development of CFS in people with IBS. Research published in Microbiome in 2017 found abnormal levels of gut bacteria related to chronic fatigue syndrome in patients with IBS.

And just as the cause of each remains a mystery, so does the reason they often appear together, as noted in a review in BJPsych Advances in June 2018.

“These are complex conditions that involve many factors,” says Lin Chang, MD, the director of the digestive health and nutrition clinic and a professor of medicine at the David Geffen School of Medicine at the University of California in Los Angeles.

Symptoms and Diagnosis of the 2 Conditions

IBS is a disorder of the gut-brain interactions, according to the Cleveland Clinic. With IBS, your bowels stop working the way they should, causing abdominal pain and a change in bowel habits — like diarrhea, constipation, or both.

A doctor may try and diagnose the condition after you’ve experienced consistent stomach pain for at least one day a week in the previous three months, according to Mayo Clinic.

There is no test that will definitely diagnose IBS, according to Mayo Clinic. A diagnosis is based on unexplained abdominal pain with constipation, diarrhea, or both, for at least three months. Your doctor may choose to do additional testing including blood tests, stool tests, a colonoscopy, a CT scan, or an upper endoscopy, to ensure that nothing else is going on.

Chronic fatigue syndrome is a condition that involves being more than just tired. According to the Centers for Disease Control and Prevention (CDC), CFS is marked by an unexplained, persistent fatigue that lasts for at least six months and isn’t helped by rest. Since there’s no test to diagnose it, doctors rely on symptoms to make a determination.

One of two of the following symptoms is required for diagnosis.

Problems with thinking and memory
Worsening of symptoms while standing or sitting upright, such as blurry vision, dizziness, and light-headedness

Other common symptoms of CFS include

Muscle pain
Headaches
Joint pain
Sore throat
Tender lymph nodes

These symptoms can resemble those of other diseases or conditions, so first your doctor will need to rule out other causes before making a definitive diagnosis of CFS.

5 Possible Ways the Conditions Are Connected

So, what’s the connection between the two conditions? Dr. Chang says that many factors may contribute to the development of both conditions. Here are some possible scenarios.

1. Post-infectious syndromes IBS sometimes develops after a stomach bug or food poisoning, says Chang. Likewise, CFS has been seen in people after a bacterial, viral, or parasitic infection. “In fact, in chronic fatigue, one of the biggest theories is that some sort of infection is causing the symptoms,” she says.

Studies have linked giardia infection, or giardiasis, with the development of both IBS and CFS. An outbreak of giardiasis in contaminated water in Bergen, Norway in 2004 sickened more than 1,200 people who developed diarrhea, stomach pain, and other intestinal problems. Follow up research found that exposure to the parasite was associated with long-term complications up to 10 years later.

2. Overactive immune response In IBS, scientists theorize that an immune response in the gut could trigger changes in secretions or the way the bowel moves or senses pain, causing symptoms, says Chang. In CFS, she says, a problem in the immune system may cause production of inflammatory substances that are linked to fatigue.

3. An imbalance in gut bacteria Research suggests that people with CFS may have abnormal levels of certain gut bacteria. A study published in the journal Microbiome found that people with CFS had higher levels of specific gut bacteria and lower levels of others compared with the gut bacteria of individuals without the condition. The researchers then checked to see if these imbalances were shared by patients who also had IBS. The results showed that participants did indeed have different patterns of gut bacteria abnormalities depending on whether they had both conditions or chronic fatigue syndrome alone. While the relationship between gut bacteria levels and chronic fatigue syndrome is not well understood, some researchers hypothesize that these disturbances may play a role in causing the condition.

4. Enhanced pain perception People with IBS and possibly those with chronic fatigue syndrome tend to process pain differently from people without the conditions. Chang explains it this way: “Say I have IBS or another chronic pain condition and you don’t, and someone applies intense pressure to our thumbnails. At the same [applied] pressure, I’ll feel it as a much more intense pain. I will rate it as 8 out of 10, and you’ll rate it as 2 out of 10. The pressure threshold that I feel pain will be lower than yours.” Up to 96 percent of patients with IBS report bloating or bowel distension, according to research in Gastroenterology and Hepatology. The feeling can range from mild discomfort to severe pain.

5. Genetic predisposition Researchers are also looking at whether gene variations make people more vulnerable to getting IBS, chronic fatigue, or another functional syndrome.

Environmental factors including stress may contribute to the development of these conditions or trigger a flare, Chang says. “It’s possible that the combination of chronic stress and a certain genetic type would predispose an individual to getting IBS and chronic fatigue syndrome,” she adds.

Treating Chronic Fatigue Syndrome and IBS

When IBS and chronic fatigue overlap, you may face a unique set of challenges.

For CFS, there is no cure or approved treatment, according to the CDC. But some symptoms like malaise, stress, and pain can be individually treated.

IBS treatment is also directed toward symptoms, according to Johns Hopkins Medicine. Treatment can often take the path of dietary changes, medications or psychotherapy.

“You have to treat multiple symptoms, and patients have a harder time managing their symptoms because it’s overwhelming sometimes,” says Chang. In addition to specific symptom treatments, Chang uses interventions that she says are useful for both conditions.

Cognitive behavioral therapy Talk therapy can give you tools to manage your condition, provide you with some sense of control, and help you feel less overwhelmed.
Medications that reduce pain Talk to your doctor about the nonnarcotic medications that may help reduce the pain of both conditions.
Lifestyle changes Routine activities and daily structure, and taking care not to overexert yourself, can ease symptoms of both IBS and chronic fatigue.

Chang adds that improvements in your mood and sleep will go a long way toward alleviating both conditions.

Additional reporting by Zachary Smith.