The Dissociative Subtype of PTSD Interview (DSP-I): Development and Psychometric Properties.

The inclusion of the dissociative subtype of post-traumatic stress disorder (PTSD-DS) in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) reflects the importance of assessing PTSD-DS. We developed the Dissociative Subtype of PTSD Interview (DSP-I). This clinician-administered instrument assesses the presence and severity of PTSD-DS (i.e., symptoms of depersonalization or derealization) and contains a supplementary checklist that enables assessment and differentiation of other trauma-related dissociative symptoms (i.e., blanking out, emotional numbing, alterations in sensory perception, amnesia, and identity confusion). The psychometric properties were tested in 131 treatment-seeking individuals with PTSD and histories of multiple trauma, 17.6 % of whom met criteria for PTSD-DS in accordance with the DSP-I. The checklist was tested in 275 treatment-seeking individuals. Results showed the DSP-I to have high internal consistency, good convergent validity with PTSD-DS items of the CAPS-5, and good divergent validity with scales of somatization, anxiety and depression. The depersonalization and derealization scales were highly associated. Moreover, the DSP-I accounted for an additional variance in PTSD severity scores of 8% over and above the CAPS-5 and number of traumatic experiences. The dissociative experiences of the checklist were more strongly associated with scales of overall distress, somatization, depression, and anxiety than scales of depersonalization and derealization. In conclusion, the DSP-I appears to be a clinically relevant and psychometrically sound instrument that is valuable for use in clinical and research settings.