Objective: Despite its long and auspicious place in the history of psychiatry, dissociative identity disorder (DID) has been associated with controversy. This paper aims to examine the empirical data related to DID and outline the contextual challenges to its scientific investigation.
Methods: The overview is limited to DID-specific research in which one or more of the following conditions are met: (i) a sample of participants with DID was systematically investigated, (ii) psychometrically-sound measures were utilised, (iii) comparisons were made with other samples, (iv) DID was differentiated from other disorders, including other dissociative disorders, (v) extraneous variables were controlled or (vi) DID diagnosis was confirmed. Following an examination of challenges to research, data are organised around the validity and phenomenology of DID, its aetiology and epidemiology, the neurobiological and cognitive correlates of the disorder, and finally its treatment.
Results: DID was found to be a complex yet valid disorder across a range of markers. It can be accurately discriminated from other disorders, especially when structured diagnostic interviews assess identity alterations and amnesia. DID is aetiologically associated with a complex combination of developmental and cultural factors, including severe childhood relational trauma. The prevalence of DID appears highest in emergency psychiatric settings and affects approximately 1% of the general population. Psychobiological studies are beginning to identify clear correlates of DID associated with diverse brain areas and cognitive functions. They are also providing an understanding of the potential metacognitive origins of amnesia. Phase-oriented empirically-guided treatments are emerging for DID.
Conclusions: The empirical literature on DID is accumulating, although some areas remain under-investigated. Existing data show DID as a complex, valid and not uncommon disorder, associated with developmental and cultural variables, that is amenable to psychotherapeutic intervention.
Keywords: Dissociative identity disorder; aetiology; phenomenology; psychobiology; treatment; validity.