I'm on Disability too. I understand exactly what you are talking about. I have Lyme Disease, so sometimes I blame it on that, even though I am experiencing mental problems. Lyme causes mood swings anyway, so even that can be Lyme related and I do have Bipolar as well as PTSD.
I hate the stigma. My mother had to tell me when I was very young NEVER to mention that she had, had a "nervous breakdown." I was told in no uncertain terms that there would be dire consequences from others, because of the stigma, for our whole family if I were to say anything about this at all.
I do find that people are concerned and want to know why I was in the hospital a few weeks ago. They assumed it was Lyme related and I did not tell them otherwise. I don't really know if that is a lie, because frankly, to some degree, when I have been so stressed by mental stuff, it has exhausted me physically to the point that I don't feel like doing much of anything other than what I absolutely have to. My Lyme can cause that too, so I have no idea what is what anymore. All I know is that I needed help and when I went to my pdoc this week, she even gave me something for my arthritis, so I was grateful that she saved me a visit to my regular Dr. I will go in January to that Dr. anyway, but hey, saving a co-pay is no small thing these days!