In 2011, sitting at a restaurant with friends, Jennifer Brea was about to sign the check for her meal when she discovered she no longer knew how to write her name.

“I couldn’t tell my hands how to move,” she said. “I couldn’t draw the side of a circle.”

The moment was a turning point for Brea, who over the next few weeks rapidly deteriorated until, she said, “I became too weak to even sit up in a wheelchair.” A Ph.D. student in Harvard’s government department at the time, “I would be in lecture, and I would understand each individual word the professor was saying, but I could not for the life of me form meaning from the sentences.” Sometimes, she said, “I would lose the ability to think or speak in any language.”

For almost two years, Brea went through 15 different doctors and a host of different diagnoses, none of which seemed to fit her symptoms: She was told she was suffering from final-exam stress, she said, or an inner-ear infection, or depression, or conversion disorder. “One of my neurologists told me that all my symptoms were being caused by some distant trauma that I might not be able to recall,” she said.

From her own online research, Brea suspected chronic-fatigue syndrome, an incurable condition described by the Centers for Disease Control and Prevention as “unexplained, severe fatigue lasting at least six months that is not improved by bed rest.” While scientists have been unable to definitively pinpoint a cause, many believe that a viral infection can be a trigger; Brea traces her symptoms back to a 10-day period in 2011 when she battled a 104-degree fever. Eventually, she flew from Boston to Miami, where a chronic-fatigue specialist confirmed her suspicions.

Current estimates place the number of chronic-fatigue sufferers in the U.S. somewhere between 836,000 and 2.5 million, though less than 20 percent of those people have actually been diagnosed, according to the CDC. But patients in Brea’s situation may soon have an easier time attaching a name to their symptoms: In a study published last week in the journal Science Advances, researchers found that people with chronic-fatigue syndrome showed measurable differences in their immune systems, a discovery that may enable doctors to diagnose the disease more quickly down the road—and one that sheds more light on its still-mysterious biological origins.

“It’s been a highly stigmatized disorder. There’s been many naysayers that don’t even believe it’s a biological disorder,” said Mady Hornig, the lead researcher and a professor of epidemiology at Columbia University’s Mailman School of Public Health.

For their study, Hornig and her colleagues analyzed blood-plasma samples from 298 patients who had been diagnosed with chronic-fatigue syndrome and 348 healthy volunteers. People who had had the disease for three years or less, they found, had elevated levels of certain cytokines—a type of immune-system molecule found in the blood—compared the healthy control group, while those who had been sick for longer periods of time had lower levels.

“This was a much more profound set of immune changes than had been seen before,” Hornig said. “We think it holds promise for earlier diagnosis”—although, she added, “we need more validation” before the research can be translated into any clinical applications. Currently, she and her colleagues are running a longitudinal study with a subset of the same group of patients, looking at how their individual cytokine levels change over time.

The paper is the second in recent months to describe physical differences linked to the disease: In October, researchers at Stanford University observed differences in the white matter of the brains of patients with chronic-fatigue syndrome, a finding that Drew Foster described in The Atlantic as “a social-legitimacy jackpot.”

“The findings get us almost no closer to a treatment for or even an understanding of what causes the condition,” Foster noted—but still, the study “[gave] the condition an objectively observable organic basis, which is the gold standard for social recognition of suffering in Western culture.”

And both studies’ arguments for the legitimacy of chronic-fatigue syndrome are bolstered by an Institute of Medicine report, released last month, that suggests new criteria for diagnosing the disease. Under the proposed guidelines, a patient would have to have “a substantial reduction or impairment in the ability to engage in pre-illness levels” of activity for more than six months, “post-exertional malaise,” and “unrefreshing sleep,” as well as either cognitive impairment or “orthostatic intolerance,” an inability to stand upright.

The IOM report also suggested a possible name change, to systemic-exertion intolerance disease. Referring to the condition as chronic-fatigue syndrome “can trivialize the seriousness of the condition and promote misunderstanding of the illness,” the report said, while the more scientific-sounding alternative, myalgic encephalomyelitis (ME), “is not appropriate because there is a lack of evidence for encephalomyelitis (brain inflammation) in patients with this disease, and myalgia (muscle pain) is not a core symptom.”

But Brea prefers to refer to her disease as ME, arguing that the IOM’s suggestion “still sounds like a euphemism for lazy”—a claim that patients say has held up diagnoses, research funding, and acceptance of the disease. “In some ways, I think the name is almost as important as the truth,” she said. With chronic-fatigue syndrome, “There’s this idea of, ‘Oh, well, I’m tired, too.’ Fatigue is not just tiredness—fatigue is not being able to lift my head off the pillow. They’re very different physiological things.”

“What people think of as fatigue is something you never experience [as a chronic-fatigue patient],” agreed Roger King, the author of Love and Fatigue in America, a fictionalized account of his own experience with the disease. “You comprehensively malfunction before you get tired.” He also prefers ME, he said, “because it sounded like a real illness.”

But while Hornig believes her study will help popularize the idea of chronic-fatigue syndrome as a “real illness”—“we’re ready to start dismantling these lingering misinterpretations of what this disorder means,” she said—she also sees it as a call for additional resources. Her work is funded by a private foundation; the National Institutes of Health have budgeted $5 million for research into chronic-fatigue syndrome for 2015, one of the smallest amounts on its itemized list of projected spending. (For context, headaches were allotted $24 million, and multiple sclerosis $103 million.) “The Institute of Medicine has agreed that this is a biological disorder, and there needs to be more research,” she said.

“One study is a drop in the bucket,” Brea agreed. “For this study to be taken seriously, there has to be money to do it again.”