A comparison between auditory hallucinations, interpretation of voices, and formal thought disorder in dissociative identity disorder and schizophrenia spectrum disorders

Objectives
Dissociative identity disorder (DID) and schizophrenia-spectrum disorders (SSD) share some overlapping phenomenological features making accurate diagnosis more difficult. Childhood abuse and depersonalization have been associated with psychotic symptoms across psychological disorders but their relationship to psychotic phenomenology remains understudied.

Method
The present study used quantitative measures to examine (1) similarities and differences in phenomenological voice hearing experiences, interpretations of voices, and thought disorder symptoms in individuals with DID (n = 44) or SSD (n = 45), and (2) whether depersonalization and childhood maltreatment influenced the initial pattern of findings.

Results
DID participants perceived their voices as being more internally located and generated, louder, and uncontrollable than SSD participants. Furthermore, the DID participants endorsed a greater frequency of thought disorder symptoms. Adding the covariates (sex, depersonalization, and child maltreatment) did not change the findings associated with location and origin of voices, and derailment, but there were now no differences in loudness or controllability. However, the schizophrenia sample reported more distress and metaphysical beliefs associated with voices, as well as more thought disorder incoherence and word substitution with the covariates controlled.

Conclusion
While tentative, metaphysical interpretations of voices, incoherent thoughts and word substitution may reflect more psychotic processes.