Previous empirical studies on the relationship between psychotic symptoms and dissociative disorders focused on auditory hallucinations only or employed limited statistical analyses. We investigated whether the frequency of Schneiderian first rank symptoms (FRS) predicts the presence or absence of a dissociative disorder (DD). Psychiatric in-patients (n = 116) completed measures of dissociation, FRS and general psychological distress (GPD). DD diagnoses were confirmed by multidisciplinary teams or administering the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised (SCID-D-R). The FRS were recorded in the Multidimensional Inventory of Dissociation (MID) and a mean score obtained for 35 relevant items: Voices arguing, voices commenting, made feelings, made impulses, made actions, influences on body, thought withdrawal, and thought insertion. A global severity index (GSI) of GPD was obtained from the Symptom Checklist-90-Revised (SCL-90-R). Logistic regression models examined whether FRS predict diagnostic classification of patients under a DD (n = 16) or not (n = 100), controlling for GSI. The overall fit of the model was significant (p = .0002). DD was correctly classified using frequency of FRS, controlling for GSI. The latter was moderately associated with FRS (r = 0.56). FRS more than doubled the odds of a DD diagnosis (odds = 2.089; 95% CI = 1.409-3.098; correct classification rate 87.1%). The study provides convincing evidence that FRS are closely related to DDs. FRS should alert clinicians to consider DDs in differential diagnosis of psychiatric in-patients. Future research should analyze whether FRS also predict a diagnosis of schizophrenia or other psychiatric disorders.
Keywords: Dissociation; Schneiderian first rank symptoms; dissociative disorder; psychiatric in-patients; psychosis; psychotic disorder; schizophrenia.