 -- A new study by a team of researchers from Stanford University sheds light on chronic fatigue syndrome, which is estimated to affect over 836,000 Americans and has no known cure or cause, according to the U.S. Centers for Disease Control and Prevention.

Chronic fatigue syndrome (sometimes referred to in medical literature as myalgic encephalomyelitis/chronic fatigue syndrome, or ME/CFS) is a debilitating illness characterized by overwhelming fatigue that is not improved by rest, according to the CDC.

The cause of ME/CFS has baffled researchers for decades, and the CDC estimates that approximately 90 percent of people with ME/CFS have not been diagnosed.

“Chronic fatigue syndrome can turn a life of productive activity into one of dependency and desolation,” Jose Montoya, M.D., the lead author of the study, published Monday in The Proceedings of the National Academy of Sciences, said in a statement.

The study found that people with chronic fatigue syndrome had substantially higher levels of certain cytokines, substances from the immune system, in their blood. Researchers found that the higher the levels of certain pro-inflammatory cytokines, the more severe the symptoms of chronic fatigue syndrome were in patients, and the researchers suggested there is a link between excess inflammation and the disease.

“There’s been a great deal of controversy and confusion surrounding ME/CFS — even whether it is an actual disease,” the study's senior author, Mark Davis said in a statement, adding that the new research provides “a solid basis for a diagnostic blood test.”

ABC News’ senior medical contributor, Dr. Jennifer Ashton, said that the study should encourage patients with ME/CFS that researchers have not ignored their pain, even if many questions surrounding the disease remain.

The new research may encourage patients who have felt the disease was all in their head.

“I have seen the horrors of this disease, multiplied by hundreds of patients,” Montoya said in the statement. “It’s been observed and talked about for 35 years now, sometimes with the onus of being described as a psychological condition. But chronic fatigue syndrome is by no means a figment of the imagination. This is real.”