"It felt very special, it felt customised to me"-A qualitative investigation of the experiences of participating in a clinical trial of CBT for young people at risk of bipolar disorder.

Objectives: The Bipolar at Risk Trial (BART) was a feasibility randomized controlled trial investigating cognitive behavioral therapy (CBT) compared with treatment as usual (TAU) in young people at high risk of developing bipolar disorder (BD). This qualitative study aimed to investigate participants' experiences of trial involvement, and the acceptability of CBT for this population.

Design: Participants were those identified as being at risk of bipolar disorder, determined by current symptoms or family history. A purposive sample of twenty-one participants from both the intervention and TAU arms of the trial was recruited.

Methods: Twenty-one semi-structured interviews were conducted by service user researchers (13 participants had received therapy and 8 TAU). Interviews were audio recorded with consent from participants and transcribed verbatim. NVivo 11 Pro software was used to conduct an inductive thematic analysis.

Results: Super-ordinate themes were "adaptability and flexibility," "feeling understood and valued," and "relevance of study and intervention" which had two sub-themes-"value of the trial therapy" and "acceptability of trial processes." Participating in the trial and having therapy enabled participants to feel understood and valued by research assistants (RAs) and therapists. Participants viewed therapy as relevant to their current concerns and valued adaptability and flexibility of RAs and therapists.

Conclusions: Findings highlight the importance and value of flexibility, adaptability, and understanding in relationships between participants and trial staff. Findings also indicate that the trial processes and CBT focusing on mood swings are acceptable and relevant to participants from this at risk population.

Practitioner Points: Young people at risk of bipolar disorder value a flexible approach to assessments and therapy, developing a rapport with research assistants and therapists and opening up to them when they feel comfortable to do so. CBT focusing on coping with mood swings was acceptable to the majority of participants who received it and it was perceived as helpful in ways that were personal to each participant.