Depersonalisation-Derealisation Disorder (DDD) is a mental health condition that people often have a hard time describing. In their Mental Elf blog, a team of mental health staff from the University of Edinburgh (2020) report that people characterise DDD with negative feelings of disconnection or detachment from themselves or the world around them. For example, people feel they’re in a simulation or watching the world through Perspex (Černis et al. 2020).
DPDR affects around 2% of the general population (Yang et al., 2023) and falls under the category of dissociative disorders in diagnostic criteria (e.g. the ICD-11). Currently, there is limited guidance on specific treatments for DDD, although the prevalence reaches similar percentages to OCD (~2-3%) and is twice as common as schizophrenia (~0.5-1%) (Hunter et al., 2004). Despite this, the NHS (2023) recommends talking therapy, Eye Movement Desensitisation and Reprocessing (EMDR) and medication for the treatment of dissociative disorders in general. Hunter et al. (2026) conducted a feasibility study investigating CBT for DDD.
DPDR is a dissociative disorder affecting ~2% of the population with limited treatment guidance, prompting Hunter et al. (2026) to investigate CBT as a potential intervention.
Methods
Thirty participants were recruited via three London NHS Trusts, across primary, secondary, and tertiary services, and randomly allocated to CBT-f-DDD or treatment as usual (TAU). Assessors and statisticians were blinded to allocation.
Participants completed assessments at baseline and at one, six, and nine months. These included the Cambridge Depersonalisation Scale (CDS) and a range of standardised measures. Those in the CBT condition received individual therapy over six months; those in TAU recorded whatever interventions they were offered during this time. Qualitative interviews were conducted after nine months with CBT participants and clinicians.
Clinicians attended a half-day training workshop, were provided with a manualised CBT-f-DDD protocol, and received fortnightly group supervision.
Results
Hunter et al. (2026) aimed to assess feasibility by evaluating the following eight objectives:
Recruitment
Most of the participants (73%) were recruited from Talking Therapies Services, and 90% of participants were registered to services in the Camden & Islington NHS Trust.
The recruitment rate for the study averaged 2.3 participants per month. This was lower than the authors had estimated, meaning that the study design was changed to allow for a longer recruitment period.
Retention
Three participants formally withdrew from the study. Two in the CBT group and one in the TAU group.
- Assessment: The percentage of participants who completed the outcome measures was 87% at time 1 (1-month), 80% at time 2 (6-months) and 63% at time 3 (9-months).
- Therapy: 54% of participants completed more than 6 sessions of CBT-f-DDD, 23% completed 2-5 sessions, and 23% completed no sessions.
Resources
Attendance to CBT-f-DDD was lower than that of the TAU group, 76% vs. 90% attendance, respectively.
- Staff resource: The research assistant completed approximately 171 hours of data collection and entry, and a total of 120 hours of clinical supervision was provided.
- Treatment Fidelity: A random sample of 10% of therapy sessions was assessed using the Cognitive Therapy Scale (CTS-R) (Blackburn et al. 2001) and was rated as competent. Therapists rated their clients’ engagement with therapy as excellent, very good or good in 56%, average in 22% and no/minimal in 22% of participants.
Representativeness
Most of the sample were female (60%) with a mean age of 27 years (SD=5.77). This differs somewhat to the prevalence data which suggests that DDD affects males and females equally, with age of onset typically being before the age of 25 (Wilkhoo et al. 2024). The older age group in this study possibly highlights the difficulties people have in identifying DDD, meaning it may take longer to access support.
The median age of DDD becoming chronic was 20 years old, and the median duration was four years.
Acceptability of data collection
Satisfaction questionnaires completed by 22 of 30 participants revealed that more than 50% of participants were somewhat or extremely satisfied with the assessment process, questionnaires used and how queries were dealt with.
Overall, participants in the TAU group rated their experience more negatively than those in the CBT-f-DDD group.
Acceptability of intervention
54% of participants in the CBT-f-DDD group were extremely or somewhat satisfied with the therapist they worked with, and 46% rated their treatment outcome positively, with 46% also stating that their symptoms improved since receiving treatment.
Response to intervention
Those in the CBT-f-DDD condition reported a 16.88 point (SD=43.57) mean decrease in scores on the Cambridge Depersonalisation Scale (CDS) compared to a decrease of 5.5 points (SD=24.96) in the TAU condition. This result suggests that CBT-f-DDD resulted in a larger decrease in reported depersonalisation scores compared to TAU. The paper focuses on CDS as the primary outcome; change scores for other measures, including the Dissociative Experiences Scale-II (DES-II), are not discussed in the results.
Health economics
In this study, CBT-f-DDD costs approximately £90 more than TAU. When accounting for societal costs, CBT-f-DDD saves approximately £153/person and increases a person’s quality of life by around 1 month (0.08 Quality-Adjusted Life Years).
This feasibility trial suggests that a full RCT of CBT-f-DDD is viable, with preliminary signals that the intervention may reduce symptoms more than treatment as usual.
Conclusions
This feasibility trial suggests that a full RCT of CBT-f-DDD is warranted, with preliminary signals that the intervention may reduce symptoms more than treatment as usual and carry societal cost benefits.
However, recruitment was slower than anticipated and retention rates need improvement before a larger trial is attempted. Clinicians were successfully trained to deliver CBT-f-DDD, though the authors suggest a longer training period and more in-person sessions would improve delivery.
The authors also recommend improving the experience for those in the TAU condition, as this group rated their overall experience more negatively.
Overall, the findings support progression to a larger, adequately powered trial, with refinements to recruitment, retention, and intervention delivery.
Preliminary health economic analyses suggest CBT-f-DDD may offer societal cost savings, but these findings need replication in a larger, fully powered trial.”
Strengths and limitations
This study offers an important step towards developing an evidence base for CBT-f-DDD, given the limited data available, and provides preliminary signals about the potential effect of the intervention, alongside useful data on cost implications and the acceptability of the study protocol.
The authors acknowledge limitations with the slow recruitment rate, partly attributed to variable engagement from some NHS services. This highlights the broader challenge of identifying and recruiting people with DDD within services that lack routine assessment or specific coding for the condition. The study already drew on the charity Unreal for recruitment; future studies might extend this further, including recruiting from the general public, to capture those who struggle to access mainstream services.
The study’s eight objectives is standard practice for feasibility trials, but separating the feasibility and preliminary efficacy questions from the health economics in a future study could allow for a more focused design.
The paper states that participants met DSM-5 criteria for DDD, but the process by which this was established is not fully described. Given that DDD can be mistaken for anxiety disorders and other conditions, greater clarity on the diagnostic procedure would strengthen a future trial, for example, specifying whether diagnoses were confirmed by a psychiatrist or specialist clinician.
The TAU condition asked participants to record interventions offered to them, but it is unclear whether they engaged with these. Future trials might consider a waiting list or alternative therapy comparison to allow a more direct assessment of whether the specific components of CBT-f-DDD add value over and above general support.
The training provided to clinicians was focused on delivering CBT-f-DDD rather than identifying the condition. Given that DDD is often underdiagnosed and can present similarly to anxiety disorders, future studies would benefit from clearer guidance on assessment procedures, and might consider hiring independent clinicians with relevant expertise to ensure diagnostic accuracy.
This feasibility trial is a valuable first step toward an evidence base for CBT-f-DDD, though refinements to recruitment, diagnostic procedures, and clinician assessment are needed before a full trial.
Implications for practice
This study provides a valuable starting point for developing both understanding and treatment of DDD. Identifying an intervention that may be tailored to those who experience this difficult-to-describe condition offers real potential for more targeted, meaningful support.
Therapy services would benefit from further education on the symptoms of DDD and how to identify them when people seek help. Clinicians should listen for metaphorical descriptions such as ‘I am in an invisible fog’. Explaining why dissociative symptoms occur and signposting to peer support can help normalise the experience (Černis et al., 2025), improving outcomes particularly where DDD presents alongside trauma or post-traumatic stress disorder.
If future adequately powered trials confirm that individual CBT-f-DDD is effective, a natural next step would be to explore whether this could be adapted into a group format. Group interventions can offer social support, normalisation of symptoms, and opportunities for peer learning — all potentially valuable for people living with DDD (Beard et al., 2024).
Better clinician education on DDD’s distinct symptoms, alongside exploring scalable formats like group CBT-f-DDD, could help translate promising early findings into real-world support for those affected.
Statement of interest
Rachael Bowes has no conflicts of interest to declare. Rachael has an interest in the topic of dissociation, and her doctoral research project aims to explore the experiences of depersonalisation in depth.
Edited by
Dr Dafni Katsampa.
Links
Primary paper
Elaine Hunter, Lucy Ring, Rafael Gafoor, Nicola Morant, Glyn Lewis, Joe Perkins, Nicola Dalrymple, Ana Dumitru, Cheuk Lon Malcolm Wong, Elena Pizzo, Georgia McRedmond & Anthony David (2026). Cognitive Behavior Therapy for Depersonalization-Derealization Disorder (CBT-f-DDD): a feasibility randomized trial. Pilot and Feasibility Studies, 12(1), 9.
Other references
Beard, D., Cottam, C., & Painter, J. (2024). Evaluation of the perceived benefits of a peer support group for people with mental health problems. Nursing Reports, 14(3), 1661-1675.
Blackburn, I. M., James, I. A., Milne, D. L., Reichelt, F. K., Garland, A., Baker, C., … & Claydon, A. (2001). Cognitive therapy scale—revised (CTS-R). Newcastle-upon-Tyne: Newcastle Cognitive and Behavioural Therapies Centre.
Černis, E., Freeman, D., & Ehlers, A. (2020). Describing the indescribable: A qualitative study of dissociative experiences in psychosis. PLoS One, 15(2), e0229091.
Černis, E., Antonović, M., Kamvar, R., Perkins, J., Transdiagnostic DPDR Project Lived Experience Advisory Panel, Chandler, L., … & Njoroge, J. (2025). Depersonalisation-derealisation as a transdiagnostic treatment target: a scoping review of the evidence in anxiety, depression, and psychosis. Frontiers in Psychology, 16, 1531633.
Cernis, Emma; Suter, Gwynnevere; Webb, Gwendalyn; Perkins, Joe; Sinfield, Eleanor; Kamvar, Roya (2025). Through the fog: Getting help for dissociation & depersonalisation. figshare. Online resource.
Hunter EC, Sierra M, David AS. The epidemiology of depersonalisation and derealisation. A systematic review. Soc Psychiatry Psychiatr Epidemiol. 2004 Jan;39(1):9-18. doi: 10.1007/s00127-004-0701-4.
NHS Dissociative Disorders. https://www.nhs.uk/mental-health/conditions/dissociative-disorders/, Accessed 01 Mar 2026.
The British Psychological Society. Psychological Wellbeing Practitioner Job Profile. Accessed 01 Mar 2026.
University of Edinburgh Division of Psychiatry. Service User Experiences of Dissociation. The Mental Elf, 10 Mar 2020.
Wilkhoo, H. S., Islam, A. W., Reji, F., Sanghvi, L., Potdar, R., & Solanki, S. (2024). Depersonalization-derealization disorder: etiological mechanism, diagnosis and management. Discoveries, 12(2), e190.
Yang, J., Millman, L. M., David, A. S., & Hunter, E. C. (2023). The prevalence of depersonalization-derealization disorder: a systematic review. Journal of Trauma & Dissociation, 24(1), 8-41.
