Assessment of acceptability of intervention and study procedures

Acceptability will be examined quantitatively through study uptake, attrition and retention rates as well qualitatively through interviews because participants’ experiences of participation in a trial and its procedures (e.g. quantity and frequency of assessments, randomisation process) are important for informing the design and methods of a future full-scale RCT. In addition, the acceptability of the intervention will be assessed through a validated satisfaction questionnaire [68] and through qualitative research interviews (described below) in order to examine if the current intervention is considered to be acceptable and appropriate for this population.

The Client Satisfaction Questionnaire [68] will be used to collect information on participants’ views on the acceptability of Baby Triple P and their overall satisfaction with this intervention. Participants are asked to rate 13 questions (e.g. to what extent has the programme met your needs?) on a 7-point Likert scale and provide answers to three open-ended questions (e.g. do you have any other comments about this programme?). This will be administered to participants (allocated to receive Baby Triple P plus TAU) in person or over the telephone or via post after they have completed the intervention.

Semi-structured individual interviews will be conducted post-intervention with MBU staff and trial participants allocated to the intervention arm prior to or around the time of their final follow-up assessment. All participants will be given a separate participant information sheet and consent form. Staff participants will be recruited through an advert or poster displayed on the ward. All interviewees will be interviewed at a time and place convenient to them or via telephone for up to 90 min. Interviewees will be given the choice to be interviewed by a researcher who works on the study at the same MBU they were admitted to and who they know or by a researcher who works at a different MBU and who they do not know. This is to ensure that participants feel comfortable expressing their views in the interview.

Interviews with participants and MBU staff will explore (1) acceptability, usefulness and user-friendliness of the intervention, (2) changes in and any benefits to themselves since receiving the intervention, (3) perceived changes/improvements to the intervention needed, (4) ways to increase adherence to and engagement in the intervention, (5) views on the procedures of the trial, and (6) perceived changes/improvements needed to increase adherence to and engagement in the study.