This kind of study always suffers from a problem because it confounds two things: 1) an illness suffered by patients, 2) common thinking habits of doctors. Byron Hyde argues that there is no such disease as "Chronic Fatigue Syndrome" (CFS), only Myalgic Encephalomyelitis (ME), caused by enteroviruses, and misdiagnosis. I wouldn't go that far, (I have my suspicions about herpes viruses like HHV6a,) but I have to admit that in operational terms for vast numbers of doctors CFS means some vague chronic condition with a lot of fatigue, and a label which will get them out of my clinic. As long as such thinking persists we will find any number of disparate conditions dumped into a common wastebasket, and this will confound research and treatment.
By a series of chance experiences in the past I have encountered several people with rare conditions that have happened to get swept up in the CFS basket. These include infectious, genetic and autoimmune diseases -- a wide range of causes. I will even admit that most such conditions are quite rare in clinical practice. What I will not admit is that ignoring conditions in a particular patient because they are rare in others is acceptable medical practice when you a labeled as a professional and patients are paying for something more than the generic treatment advice they could get from a television program.
Over and over again, I have been confronted with medical treatments that don't work, and doctors who persist in using them on all patients because they might work on some. If you don't pay attention to evidence your treatment option is not working in a particular patient you can do great harm, but as long as doctors are paid merely for treatment the motivation to discover that a treatment is ineffective is weak.
This is not simply a problem for treating minor chronic conditions that are never fatal.
Here is a report on new drugs prescribed to treat cancer which shows that the
majority licensed for clinical practice don't actually provide the benefits expected. Something is seriously wrong with a system that functions this poorly when dealing with life-threatening illness. Is it any wonder such a broken system functions more poorly in handling chronic conditions that are rarely fatal?
In addition, I want to point out that most cancer patients go through a prodromal phase when cancer affects their performance and general health but is not specifically indicated by clinical signs. More than one such patient has ended up with the label CFS, and this delays diagnosis and treatment of actual cancer.