The editorial entitled ‘Dissociative identity disorder: out of the shadows at last?’^{Reference Reinders and Veltman1} considers that the diagnosis has often been rejected through misleading information, and the prejudices derived therefrom, and through self-protection, a cultural dissociation from the reality of the impact of severe trauma on later clinical presentations. Psychiatrists can then choose to ‘dislike’ the diagnosis and refuse to use it in a way that would never happen, without severe medico-legal consequences, for schizophrenia or bipolar affective disorder. This occurs despite evidence that: many patients with dissociative identity disorder (DID) are severely ill and functionally impaired, have high rates of severe comorbidities, and are often at risk for non-suicidal self-injury and suicide attempts.^{Reference Langeland, Jepsen, Brand, Kleven, Loewenstein and Putnam2} However, another reason for mental health services encouraging such dismissive perspectives, and stigmatising/scapegoating those who use the diagnosis, while denying those in need of treatment, is that the treatment is considered prohibitively expensive. Medication is of limited value^{Reference Ross3} and specialist psychotherapy for DID not only takes years,^{Reference Brand, McNary, Myrick, Loewenstein, Classen and Lanius4} but recovery with therapy often has a non-linear course.^{Reference Frewen and Lanius5} As psychiatric doctors define their domains by severe and enduring mental illness, with DID omitted, training of psychiatrists remains largely devoid of mention of complex trauma and its sequelae, with DID seen then as the province of others – such as clinical psychology.

DID is usually considered to be at the most severe end of a spectrum of complex trauma disorders, but its treatment requires different skills in the therapist from those required for treating someone with post-traumatic stress disorder (PTSD) not involving structural dissociation.^{Reference Van der Hart, Nijenhuis and Steele6} There are many ways to have a diagnosis of PTSD,^{Reference Galatzer-Levy and Bryant7} so the ICD-11 diagnosis of complex PTSD,^{Reference Elklit, Hyland and Shevlin8} while welcome, will raise similar questions about the classification of individual patients with complex PTSD and DID, diagnoses which are not synonymous. Also, individuals with DID should not have diagnostic labels of non-dissociative or personality disorders, nor vaguely defined mood, anxiety or psychotic disorders, inappropriately attached to them; nor should clinicians feel the need to eschew the appropriate diagnosis of DID to avoid opprobrium, whether from other clinicians or from management. Any potential gains, service or financial, of not providing comprehensive, continuing, treatment that acknowledges causative factors are short term as there are long-term implications for morbidity and mortality, even across generations (see for example^{Reference Hesse, Main, Abrams, Rifkin, Solomon and Sigel9}). Pathological dissociation has an impact on the effectiveness, or otherwise, of specialist treatment for adults with histories of early traumatisation so its recognition is vital for treatment planning.^{Reference Jepsen, Langeland and Heir10} Moreover, a specialist online educational programme for patients and clinicians with dissociative disorders has been demonstrated to reduce non-suicidal self-injury in this group.^{Reference Brand, Schielke, Putnam, Putnam, Loewenstein and Myrick11} Clinicians should follow the evidence for DID; it has a defined aetiology and pathology, characteristic clinical features for which there are well-established structured interviews – and effective, non-pharmacological, treatments.

The development of the skills for treating DID can improve the ability to treat other disorders in which traumatic experiences have had an aetiological impact and that manifest with some expression of emotion dysregulation but, even with these additional gains, the comprehensive and effective treatment of DID will still have huge service implications. Training of staff to provide clinically relevant diagnostic formulations, and the appropriate treatments, could challenge individual ontological perspectives, and would require significant resources, but would benefit the many individuals who are burdened with the clinical manifestations of these severe post-traumatic states. There is also the distinct possibility that appropriate treatment would not be as economically burdensome as feared when the costs to society of hitherto-unrecognised disorders are compared with the costs to health services from the absence of appropriate treatment.^{Reference Langeland, Jepsen, Brand, Kleven, Loewenstein and Putnam2}