Cognitive Behaviour Therapy (CBT) for Depersonalization Derealization Disorder (DDD): a self-controlled cross-over study of waiting list vs. active treatment.

Depersonalisation-Derealisation Disorder (DDD) has a prevalence of around 1% but is under-recognised and often does not respond to medical intervention. We report on a clinical audit of 36 participants with a diagnosis of chronic DDD who were sequentially recruited from a specialist DDD National Health Service clinic in London, United Kingdom, and who completed Cognitive Behavioural Therapy specifically adapted for DDD. The sample population had a mean age of 38.7 years (s.d. = 13.4), 61% were male and 69% were of White ethnicity. Three outcomes were assessed (Cambridge Depersonalisation Scale [CDS], Beck Depression Inventory [BDI], and the Beck Anxiety Inventory [BAI]) at three time points in a naturalistic, self-controlled, cross-over design. Hierarchical longitudinal analyses for outcome response clustered by patient were performed using scores from baseline, beginning, and end of therapy. All scores showed improvement during the treatment period, with medium effect sizes. CBT may be an effective treatment for DDD. However, treatment was not randomly assigned, and the sample was small. More research is needed, including the use of randomisation to assess the efficacy of CBT for DDD.