some folks might have heard the incorrect info that folks with schizophrenia hear their verbal auditory hallucinations aka voices outside their head unlike people with dissociative identity disorder hear their voices inside their head
also folks with borderline personality disorder had their experiences of hearing voices labelled as "quasi-psychosis" and the like since psychiatry people falsely theorize it is entirely different from hearing voices as someone with schizophrenia (Merrett et al., 2016)
but both folks with schizophrenia and folks with dissociative disorders heard their voices inside or outside their head comparatively similarly: "Current and first episode location of voices was most likely internal for all groups. Challenging clinical wisdom, external current auditory hallucinations were relatively rare in the schizophrenia groups, as in the DID group. However, the schizophrenia without maltreatment group did have a greater propensity to report external voices compared with the other 2 groups. With reference to location of voices, the groups looked more similar than different, supporting previous research examining auditory hallucinations in dissociative disorders and schizophrenia." (Dorahy et al., 2009)
and both folks with borderline personality disorder and folks with schizophrenia hear voices inside versus outside their head about the same too: "In addition, the feeling that voices were heard outside or inside the head (“external/internal”) was not significantly different between the groups." (Tschoeke et al., 2014)
that is likely because folks reporting psychosis-related and psychosis-soundind experiences are not tested using the same metrics and their info is not collected, reviewed, and published the same way depending on perceived or given diagnosis (Merrett et al., 2016) because stigma 🙃