# Cognitive Behavior Therapy for Depersonalization-Derealization Disorder (CBT-f-DDD): a feasibility randomized trial

## TL;DR

This study tested the feasibility of a therapy for depersonalization-derealization disorder and found it promising but needing improvements for a larger trial.

## Contribution

The study provides the first feasibility trial of CBT-f-DDD in a randomized design, paving the way for a definitive RCT.

## Key findings

- CBT-f-DDD showed a larger reduction in DDD symptoms compared to Treatment as Usual.
- Participants reported improved quality of life at low cost, with potential economic benefits.
- Recruitment was successful, but retention was suboptimal, indicating a need for design improvements.

## Abstract

Depersonalization-derealization disorder (DDD) is characterized by feelings of “unreality” about the self and/or external world. Cognitive Behavioral Therapy adapted for DDD (CBT-f-DDD) has been effective in published clinical audits. This study aimed to provide feasibility and acceptability data.

An individually randomized design of CBT-f-DDD versus Treatment as Usual (TAU) was carried out with adult DDD participants from NHS Trusts in London. The CBT-f-DDD group received individual sessions over a 6-month period from CBT therapists. Qualitative interviews were conducted with CBT-f-DDD participants and their clinicians. Eight feasibility objectives were evaluated (recruitment, retention, resources, representativeness, acceptability of study design and intervention, preliminary responses to intervention, and health economics).

Thirty participants with DDD were recruited over 13 months. Only 63% completed the final assessment, so retention needs improvement. Resources were acceptable. The sample was comparable to previous studies, although younger, with a shorter duration of DDD and lower mean DDD scores. In a post-study questionnaire, no aspect of the study or treatment was rated unacceptable; however, some areas need improvement. Qualitative interviews with participants and clinicians recorded positive responses to CBT-f-DDD. Those in the CBT arm had a mean decrease of 16.9 points (SD 43.6) on the Cambridge Depersonalization Scale versus a mean decrease of 5.5 points (SD = 25.0) for the TAU arm. Health economics analyses found that CBT-f-DDD saved £153 per person. Participants reported an additional 0.08 Quality-Adjusted Life Years at low cost.

This study suggests that a subsequent RCT for CBT-f-DDD is feasible and represents the first step in the process of establishing evidence-based treatments for DDD. However, refinements to the current design and delivery were indicated for a future fully powered definitive RCT of CBT-f-DDD.

ISRCTN, ISRCTN97686121. Retrospectively registered 5 January 2023: https://doi.org/10.1186/ISRCTN97686121