I sometimes wonder if the voices are suppressed in the “healthy” population, but to some extent still influential - but dangerous in that they operate out of sight. For reference: non-professional opinion.
That seems like a Freudian theory of repressed trauma or the more
general idea of "coping mechanisms" that go wrong. The "healthy" mind
isn't afraid/ashamed to hear and process discomforting thoughts. For
the more fragile mind, pushing them back makes them more and more
intrusive. Ronnie Laing, Thomas Szasz, Erich Fromm, and many others
have said, variously; "Mental illness is a sane reaction to an insane
world", "In a mad world, only the mad are sane", or "Coping is making
yourself part of the problem".
That's not the same as being dismissive about the state of world, or
legitimising/glorifying real and distressing medical insanity - it's
just saying; be careful how you "cope". That said, just look around
you. Aren't intrusive voices just reason tired of us telling it to
shut up.
I’d say it’s less Freud than it is Internal Family Systems theory, which posits human personality is multiple. And we’ve somehow learned to suppress voices that we know sub-consciously to be unacceptable, maybe through socialization etc. Writing this, I make the leap to Jung and need for awareness and management of these suppressed voices before they overwhelm us.
I’m conscious I am (maybe we are) fumbling towards statement or acknowledgment of the same thing.