http://pandoraorg.net/uploads/IOM_Public_Presentation__Jan_27-2.pdf Excerpt: There are many case definitions with some being very broad where the only criteria for diagnosing chronic fatigue syndrome (CFS) is 6 months of fatigue and others like the Canadian Consensus Criteria (CCC) that are concise and capture the true illness. But the multiple definitions, and overly broad definitions are causing clinician and researcher confusion. When looking at research in your study, we recommend you reject all research that focused on or only requires chronic fatigue. Those studies don’t inform you on our illness, they inform you on a symptom of many diseases. Some of you may think that a broad definition would be better for patients because a more focused definition would limit treatments. This isn’t true with ME/CFS because some of the treatments that are prescribed for idiopathic fatigue are harmful to patients. For example, someone who has depression, should be exercising more to release endorphins. Someone with ME/CFS will need to be careful to pace and not exacerbate symptoms by exercising.