Mental illness is a social construct. Even medical issues are social constructs. “Wandering uterus” used to be a medical condition in which doctors stimulated women to orgasm to “cure” them.

Every culture is going to frame things differently, but the importance is how that framing is used or held against certain people. The idea that “gender dysphoria” is a mental illness is linked to the idea that conservatives think mental illness is just weakness. They don’t believe that depression or anxiety are real, exhausting problems.