Series Buffy the Vampire Slayer question (SPOILERS)

[ChemicallyEnhanced]

I just started rewatching it for the first time (yesterday, so I'm still on season one)...and remembered that season (5? I think) episode where the twist at the end is that Buffy IS actually a catatonic in a mental hospital and has been all along and that the entire show is fantasy world she created in her head.
Do people consider that canon?
Like, even with the show continuing the rest of that season anyway - and then 2 more seasons - none of it is real?

Anyone here a fan of the show and do YOU consider it canon that Buffy is a normal, albeit severely mentally ill, girl and NOT the slayer?

 

[paranoid android]

Its been so long since ive seen buffy that i canr even remember that episode. I may have to go back and watch it again now