I'm convinced one colleague just wouldn't use the mental health illness as the actual diagnosis, when he left. He told me, since I'd had an operation, that he had the same thing, since he figured I couldn't accept stress as the reason for his departure.
I believed him, could relate, but looking back, it appears he just made the story up, to have my support.
With a powerful stigma out there, if you told someone you had cancer, or something other than a mental illness, all you'll get is a better outpouring of compassion. It's not guaranteed though, surprisingly.
I've never gone outside professionals, so it's been lonely, and it even has set up opportunities for abuse, because of that.