Depersonalisation-derealisation disorder (DDD) is an under-recognised condition, involving a sense of detachment from one’s internal processes and environment. Cognitive behavioural therapy for DDD (CBT-f-DDD) has shown promising quantitative outcomes in previous research. However, there is a lack of research examining the inner workings of CBT-f-DDD and how the treatment is experienced. This qualitative study explored the experiences and perspectives of clients who received CBT-f-DDD, and the clinicians who delivered this, to better understand acceptability, feasibility of applying CBT-f-DDD more widely in the NHS, and therapeutic processes that potentially contributed to outcomes. The study was embedded within a CBT-f-DDD feasibility randomised controlled trial in the UK. Participants consisted of clients who completed therapy and clinicians recruited from the treatment arm of the trial. Semi-structured interviews were conducted with seven clients and seven therapists after therapy. Data were analysed using codebook thematic analysis. Findings clustered into four broad domains are presented: “reception of therapy”, “possible therapeutic processes as drivers for change”, “improving the therapy”, and “treatment implementation in the NHS”. Clients expressed appreciation for being offered the opportunity to engage in CBT-f-DDD. CBT was considered an appropriate approach to treating DDD and treatment completers saw various therapeutic benefits, including a decrease in symptoms, improved relationship with DDD and higher confidence in managing dissociation. A few clients shared that interventions were not sufficiently targeted. Challenges of accommodating comorbid mental health difficulties within the CBT-f-DDD model were described by a few clinicians. Clinicians viewed CBT-f-DDD as feasible for delivery in the NHS. However, establishing effective treatment pathways and facilitating appropriate training and supervision for clinicians were considered important prerequisites. Building a strong therapeutic rapport, constructing a shared understanding of DDD and the reframing of thoughts were perceived by clients and clinicians to be crucial components connected with positive outcomes. The acceptability of CBT-f-DDD to both clients who completed therapy and clinicians was somewhat supported. The treatment was also deemed conditionally feasible for wider implementation. It is recommended that CBT-f-DDD be further refined in line with client needs, perceived mechanisms of change, professional training needs, and organisational factors. This study was embedded within a trial registered with the ISRCTN (registration number: ISRCTN97686121; registration date: 5th January 2023; https://doi.org/10.1186/ISRCTN97686121).
Wong et al. (2026) studied this question.