Their claim is evinced by the fact that only 5%–10% of people receiving treatment worsen in their symptoms.Psychiatrists August Piper and Harold Merskey have challenged the trauma hypothesis, arguing that correlation does not imply causation – the fact that people with DID report childhood trauma does not mean trauma causes DID – and point to the rareness of the diagnosis before 1980 as well as a failure to find DID as an outcome in longitudinal studies of traumatized children. They assert that DID cannot be accurately diagnosed because of vague and unclear diagnostic criteria in the DSM and undefined concepts such as "personality state" and "identities", and question the evidence for childhood abuse beyond self-reports, the lack of definition of what would indicate a threshold of abuse sufficient to induce DID and the extremely small number of cases of children diagnosed with DID despite an average age of appearance of the first alter of three years. Psychiatrist Colin Ross disagrees with Piper and Merskeys conclusion that DID cannot be accurately diagnosed, pointing to internal consistency between different structured dissociative disorder interviews (including the Dissociative Experiences Scale, Dissociative Disorders Interview Schedule and Structured Clinical Interview for Dissociative Disorders) that are in the internal validity range of widely accepted mental illnesses such as schizophrenia and major depressive disorder. In his opinion, Piper and Merskey are setting the standard of proof higher than they are for other diagnoses.
Reviews of medical records and psychological tests indicated that the majority of DID patients could be diagnosed with BPD instead, though about a third could not, suggesting that DID does exist but may be over-diagnosed. Both groups also report higher rates of physical and sexual abuse than the general population, and patients with BPD also score highly on measures of dissociation. Even using strict diagnostic criteria, it can be difficult to distinguish between dissociative disorders and BPD (as well as bipolar disorder and schizophrenia), though the presence of comorbid anxiety disorders may help.}} Causes
General
DID is etiologically complex. Şar et al. state, "Dissociative identity disorder (DID) is multifactorial in its etiology. Whereas psychosocial etiologies of DID include developmental traumatization and sociocognitive sequelae, biological factors include trauma-generated neurobiological responses. Biologically derived traits and epigenetic mechanisms are also likely to be at play. At this point, no direct examination of genetics has occurred in DID. However, it is likely to exist, given the genetic link to dissociation in general and in relation to childhood adversity in particular." Stating that there is "a lack of understanding regarding the etiopathology of DID", Blihar adds that "many researchers and psychiatrists regard DID as the most severe form of a childhood onset post-traumatic stress disorder (PTSD) because it is virtually impossible to find a DID patient without a history of PTSD. ... There are currently two competing theories regarding the relationship between trauma and dissociation: the trauma-related model and the fantasy-prone model.