I told my boss shortly after I was first diagnosed, he was actually ok and we talke a bit, turns out he'd suffered in the past. After that he was fairly useless and has even made some remarks which arn't right. I don't tell him anything at all now. I didn't even tell him when I was seeing the counsellor at work for an hour a week.
I certainly wouldn't tell a prospective future employer if I could help it, I see no reason to. Someone may be prejudice purely because it's not something they understand rather than through discrimination as such.