Following from Sykes
1. ME is not a valid disease category, there are no objective tests that prove you have it.
2. Depression is not a valid disease category, there are no objective tests that prove you have it.
For that last you could substitute almost any psychiatric diagnosis found in the DSM.
BOTH statements are fallacies. However if you believe the first its irrational and hypocritical to not believe the second. By extension, adding them all up, you would have to conclude the DSM (and ICD equivalents) or almost any psychiatric disorder are not valid disease categories.
Or you can simply admit the fallacy.
There are other arguments about the invalidity of CFS or ME diagnoses. However when you look at most psych diagnoses the picture is likely to be no better. At least ME has objective tests that reliably show pathophysiology, even if they are not yet considered diagnostic, such as NK cell function and the 2 day CPET, or for a subset the Tilt Table Test. While some pathophysiology is known for some psych disorders, its a real hodgepodge.
This blog came to me as I was waking up this morning, right after a dream in which I was exploring the USA as a tourist, on foot. The only gear I was carrying was a swag: http://www.australiandictionary.net/swag