New research out of the University of Bristol in the United Kingdom finds that chronic fatigue syndrome (CFS), or myalgic encephalomyelitis (ME), is far more common in children than previously believed. The study found that 1 in 50, or two percent, of 16-year-olds have CFS lasting over six months — and these patients missed a significant amount of time from school, about half a day per week.

Doctors did not accept chronic fatigue syndrome as a real illness until just last year, so the latest study is likely the first and biggest to examine CFS in children. Even just a few years ago, CFS was considered “unheard of,” with many doctors believing it was a made up disease. The general lack of research and information about the disease even led to many dubbing it the “yuppie flu.” However, since the Institute of Medicine accepted it as an illness in 2015, researchers are devoting more time to studying its mysterious causes and effects.

In the study, the researchers examined 5,756 kids using children of the 90s data. Girls were twice as likely as boys to be diagnosed with CFS/ME, and kids from troubled or low-income families were also more likely to have it — especially if they grew up in poor housing or had little emotional support from their mothers, (throwing doubt on the “yuppie flu” myth).

“This is an important study because it shows that CFS/ME is much more common in teenagers than previously recognized,” Dr. Esther Crawley, a consultant pediatrician with a specialty in CFS/ME and an author of the study, said in the press release. “Treatment at this age is effective for most children but few have access to treatment in the UK. Children attending my specialist service at the Royal United Hospital in Bath only attend two days a week of school on average. This means that only the most severe cases are getting help. As pediatricians, we need to get better at identifying CFS/ME, particularly in those children from disadvantaged backgrounds who may be less able to access specialist care.”

Researchers still aren’t sure what causes CFS, though it may be linked to viral infections, emotional/psychological stress, and other unknown, underlying factors. As there is no cure for the disease, doctors can only treat and alleviate some of the symptoms, characterized mainly by fatigue, memory loss, swollen lymph nodes, muscle pain, and headaches. This complicated disorder can cause depression, stress, and frequent absences from work or school, and needs to be further investigated. Further research will also help reduce the disease's stigma, especially among young people.

“We are encouraged by the results of this study as, at last, our children, their families and those fighting for a diagnosis have the evidence they need,” Mary-Jane Willows, chief executive of the Association of Young People with ME, said in the press release. “Evidence confirming the condition as being not only really common but, more significantly, evidence reflecting the high level of suffering with which they are forced to live.”

Source: Collin S, Norris T, Nuevo R, Tilling K, Joinson C, Sterne J. Chronic Fatigue Syndrome at Age 16 Years. Pediatrics, 2016.