Assessing therapeutic change in patients with severe dissociative disorders: the progress in treatment questionnaire, therapist and patient measures.

: Treatment research for dissociative identity disorder (DID) and closely related severe dissociative disorders (DD) is rare, and has been made more difficult by the lack of a reliable, valid measure for assessing treatment progress in these populations. : This paper presents psychometric data for therapist and patient report measures developed to evaluate therapeutic progress and outcomes for individuals with DID and other DD: the Progress in Treatment Questionnaire - Therapist (PITQ-t; a therapist report measure) and the Progress in Treatment Questionnaire - Patient (PITQ-p; a patient self-report measure). : We examined the data of 177 patient-therapist pairs (total = 354) participating in the TOP DD Network Study, an online psychoeducation programme aimed at helping patients with DD establish safety, regulate emotions, and manage dissociative and posttraumatic symptoms. : The PITQ-t and PITQ-p demonstrated good internal consistency and evidence of moderate convergent validity in relation to established measures of emotional dysregulation, dissociation, posttraumatic stress disorder, and psychological quality of life, which are characteristic difficulties for DD patients. The measures also demonstrated significant relationships in the hypothesized directions with positive emotions, social relations, and self-harm and dangerous behaviours. The patient-completed PITQ-p, which may be used as an ongoing assessment measure to guide treatment planning, demonstrated evidence of stronger relationships with established symptom measures than the PITQ-t. : The PITQ-t and PITQ-p merit use, additional research, and refinement in relation to the assessment of therapeutic progress with patients with DD.