It depends on how it was written in one's medical records.
Generally speaking, a diagnosis of PTSD alone, even with prescribed treatment is not sufficient to deny one their RKBA.
However, if one has been judged a danger to themselves or others, and that takes much more than just one doctor writing that in the record, then no guns for them.
"Did I say "republic?" By God, yes, I said "republic!" Long live the glorious republic of the United States of America. Damn democracy. It is a fraudulent term used, often by ignorant persons but no less often by intellectual fakers, to describe an infamous mixture of socialism, miscegenation, graft, confiscation of property and denial of personal rights to individuals whose virtuous principles make them offensive." - Westbrook Pegler