Optimising the acceptability and feasibility of novel complex interventions: an iterative, person-based approach to...

The aim of this paper is to showcase best practice in intervention development by illustrating a systematic, iterative, person-based approach to optimising intervention acceptability and feasibility, as applied to the cross-cultural adaptation of Morita therapy for depression and anxiety.

We developed the UK Morita therapy outpatient protocol over four stages integrating literature synthesis and qualitative research. Firstly, we conducted in-depth interviews combining qualitative and cognitive interviewing techniques, utilising vignettes of Morita therapy being delivered and analysed using Framework analysis to investigate potential patients and therapists' perceptions of Morita therapy. Secondly, we developed qualitative themes into recommendations for optimising Morita therapy and synthesised Morita therapy literature in line with these to develop a draft protocol. Thirdly, we conducted repeat interviews with therapists to investigate their views of the protocol. Finally, we responded to these qualitative themes through protocol modification and tailoring our therapist training programme.

As a consequence of literature describing Morita therapy and participants' perceptions of the approach, we developed both a therapy protocol and therapist training programme which were fit for purpose in proceeding to a UK-based Morita therapy feasibility study. As per our key qualitative findings and resulting recommendations, we structured our protocol according to the four-phased model of Morita therapy, included detailed guidance and warning points, and supported therapists in managing patients' expectations of the approach.

Our systematic approach towards optimising intervention acceptability and feasibility prioritises the perspectives of those who will deliver and receive the intervention. Thus, we both showcase best practice in intervention development and demonstrate the application of this process to the careful cross-cultural adaptation of an intervention in which balancing both optimisation of and adherence to the approach are key. This presentation of a generalisable process in a transparent and replicable manner will be of interest to those both developing and evaluating complex interventions in the future.