A randomised multiple baseline single case experimental design series using CBT to target mechanisms of transdiagnostic dissociation in 16-to-25-year-olds.

Dissociative experiences are prevalent in young people, where they are associated with greater clinical severity of co-occurring difficulties and increased risk of self-harm and suicide. Recent research suggests transdiagnostic dissociation plays a role in the development and maintenance of mental health problems such as anxiety, depression and psychosis, and may therefore constitute a novel early intervention target. The current study builds on our previous work developing an explanatory theoretical model of transdiagnostic dissociation by piloting therapeutic techniques that target implicated mechanisms. Our aim was to establish proof of concept, such that successful techniques could be incorporated into future treatment development. We recruited 9NHS patients (ages 16 to 23) to a series of three multiple baseline single case experimental design (SCED) studies. Every participant received four sessions of individual CBT, with each SCED addressing a different mechanism implicated in the theoretical model: cognitive appraisals of dissociation, perseverative thinking, and affect intolerance. Results across all studies were limited by low phase stability of the target measures, but indicated successful targeting of cognitive appraisals, and partial success in targeting perseverative thinking and affect intolerance. Where cognitive appraisals improved, results suggested distress about dissociation also improved. There was negligible evidence of this for perseverative thinking, buta weak positive signal for affect intolerance. Qualitative feedback from participants illustrated the need to combine therapeutic strategies into a more comprehensive intervention with more sessions. These findings inform treatment development for transdiagnostic dissociation in youth and advance understanding of its causal aetiology, supporting future research.