Chronic fatigue syndrome may not be psychological in origin after all but may be caused by bacteria in the gut.

Researchers from Cornell University have identified biological markers of the disease in gut bacteria and inflammatory microbial agents in the blood of patients with chronic fatigue syndrome, a condition where normal levels of physical exertion often lead to debilitating fatigue that can't be alleviated by rest.

"Our work demonstrates that the gut bacterial microbiome in chronic fatigue syndrome patients isn't normal, perhaps leading to gastrointestinal and inflammatory symptoms in victims of the disease," Maureen Hanson, Liberty Hyde Bailey Professor in the Department of Molecular Biology and Genetics at Cornell University and senior author of the study, said in a press release.

"Furthermore, our detection of a biological abnormality provides further evidence against the ridiculous concept that the disease is psychological in origin."

In the study, which was published in the journal Microbiome, the researchers were able to correctly diagnose 83 percent of patients with myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS) through stool and blood samples.

Researchers from the Cornell University Ithaca campus collaborated with Dr. Susan Levine, an ME/CFS specialist in New York City, and did the experiment on 48 people diagnosed with ME/CFS and 39 healthy controls.

After the experiment, the researchers sequenced regions of microbial DNA from the stool samples to identify different types of bacteria. They found that the diversity of bacteria types was greatly reduced in MS/CFS patients, and there were fewer anti-inflammatory bacterial species and more pro-inflammatory bacteria in them compared with healthy people.

According to Ludovic Giloteaux, a postdoctoral researcher and first author of the study, they were also able to find bacterial markers in the gastrointestinal system of those with the disease, which were likely caused by a leaky gut, which allowed the bacteria to enter the blood.

The bacteria in the blood will trigger an immune response and this will worsen the symptoms, researchers said.

"In the future, we could see this technique as a complement to other noninvasive diagnoses, but if we have a better idea of what is going on with these gut microbes and patients, maybe clinicians could consider changing diets, using prebiotics such as dietary fibers or probiotics to help treat the disease," Giloteaux said in a statement.

In the future, the research team will look for viruses and fungi in the gut to determine whether or not these factors contribute to the illness.