EDNOS turns out to be an acronym for Eating Disorder Not Otherwise Specified.
Which isn't at all unusual in itself, but I'm kind of amused by the idea that someone can be diagnosed as having EDNOS.
(Eating disorders themselves are obviously no laughing matter. What I'm amused by is the phrasing.)
I was also amused by the Guardian's attempted acronym expansion. I first encountered the term in an article about orthorexia nervosa. (The article reads kind of like a parody, but it appears to be serious.) It says:
Until a few years ago, there were so few sufferers that doctors usually included them under the catch-all label of "Ednos"—eating disorders not otherwise recognised.
At which I thought, wait, shouldn't that be "Ednor"? But then Wikipedia cleared it up; I assume the article's author just got confused.