Definition: CFS is the considered “diagnosis” if you have been
tired for more than 6 months, and there is no other obvious
medical disorder present.
That’s a bit like saying the sky has been blue for six months,
so there has to a drought happening.
CFS has many causes. The trick is to pick the right
one. Since there is often many causes in the same patient,
the more important trick is to pick the correct reasons and then to
treat them in the correct order.