I highly doubt that CFS is a single disease with a specific etiology. The same way depression, schizophrenia, fibromyalgia, autism are neither. They are all catch-all terms for a specific phenoype that happens to satisfy a certain set of (observable) criteria.This is preposterous. Diseases do not work like this, each disease has a specific etiology. Either CFS is one disease or many people are being lumped into it because of insufficient investigations for their actual disease. Or possibly there are more than one unnamed conditions, which is possible, symptom overlap and diagnostic criteria that are not specific enough can inadvertently say people with more than one condition have the same thing. For example the Fukuda criteria would lump people with CFS and depression because it was not good enough. The CCC or ICC are better but not yet as good as the tests used to diagnose Parkinsons for example (which has no diagnostic test at present yet has a reasonably well understood etiology and a well defined and tested diagnostic criteria).
This is a categorical statement backed up by no research. As a medical student are you not trained to look for the actual condition in question backed by medical science?