Cognitive behavioural therapy in comparison to treatment as usual in young adults at high risk of developing bipolar disorder (Bipolar At Risk):a randomised controlled trial to investigate the efficacy of a treatment approach targeted at key appraisal change: Bipolar At Risk Trial II (BART II)

Background Research has demonstrated the ability to identify and treat individuals at high risk of developing psychosis. It is possible to use a similar strategy to identify people who have an emergent risk of bipolar disorder (BD). Interventions during the early phase may improve outcomes and reduce risk of transition. Criteria have been established to identify individuals considered to be at high risk for developing BD, also known as Bipolar At Risk (BAR). Offering a psychological intervention may provide the possibility of prevention. Evaluating efficacy and the mechanisms by which this treatment works is now required. Methods A multicentre, rater-masked randomised controlled trial with two parallel arms will compare cognitive behaviour therapy (CBT) for young people meeting BAR criteria (CBTBAR) + Treatment as Usual (TAU) vs. TAU alone. Participants will be recruited from five National Health Service (NHS) sites in the UK. Outcome and mediational variables will be collected at baseline, 17-weeks (in treatment), 27-weeks (post-CBTBAR /TAU), and 52-weeks. Qualitative work will examine the perceived mechanisms of change and implementation of CBTBAR in the NHS. Discussion Our efficacy hypotheses are CBTBAR + TAU (compared to TAU alone) will lead to improvement in mood swings, a reduction in the likelihood of transition to BD, and improvements to functioning and quality of life. Our mechanistic hypothesis is CBTBAR + TAU causes improvement in mood swings due to the reduction of extreme positive and negative appraisals of internal states which in turn improves subsequent behaviours used to control mood and then internal states. Our trial will explore the perceived mechanism of change via this novel intervention (CBTBAR) and if the approach can be implemented within current services in the UK. Trial registration/Status The trial protocol is registered with ISRCTN (ISRCTN13363197, registered on 25th January 2023). Recruitment started in February 2023 and is ongoing.