@Appleblossom @FearofUnknown
I've done both at different times -- hid any sign of mental illness, and at other times let my manager (or HR) know that things were not OK.
I would actually be fine with someone bringing it up at a job interview now day - because I'd like to weed out early any employer/manager who isn't understanding of it! If they have prejudice to mental illness, then they're not the employer I want to be working with.
I have had a work colleague use the knowledge of my mental illness against me in the workplace - but my manager shut them down very quickly when they tried to use it as a prejudice despite being unrelated / non-impacting on the matter at hand. This is the manager who I had felt comfortable to let know when I was having difficulties coping with work situations (which initially was not due to my MH - it was workplace problems), and from her response to that I was later able to be "real" with her about how the workplace stressors were impacting my MH. She was fantastic. I remember one time saying to her "if possible, can I please not be assigned any work currently on the topic of xxx" - she did not question why, she just agreed unquestioningly. She could read the "why" without being told because she knew of my mental illness that was related to that piece of work topic and was at the time triggering for me to work on.