Whoa dude, I'm on Prednisone (for a severe allergic reaction to a substance) right now and I'm telling you I've been delusional as all get out! I'm still slightly delusional if you want to know the truth of it (and I don't have any sort of delusional/psychotic disorder or anything), but I'm kinda questioning the delusons at this point because my taper has been lowered.
Prednisone and all other corticosteroids are well known to cause a variety of negative mental affects. You gotta have good people around that can watch you if something like that should happen.

Luckily my delusions haven't been harmful and I'm not elderly. My T has been really helpful.