Summary of review finding	Studies contributing to the review finding	Methodological limitations	Coherence	Relevance		Adequacy	CERQual assessment of confidence in the evidence	Explanation of CERQual assessment
Finding 9: The decision to participate is discussed with a range of other people; family, friends, HCPs, previous trial participants	Smyth 2011, Abhyankar 2016, Madsen 2007b, Gopinath 2013, Habersack 2013, Oud‐Rengerink 2015, Chin 2016, Harrop 2016a, Hughes‐Morley 2016, Ballantyne 2017, de Lacey 2017, Dellson 2018,	Minor concerns based on the assessment of nine studies with no, and three studies with minor methodological limitations	Minor concerns		Minor concerns regarding relevance as studies had moderate geographical spread Included a range of medical/surgical, oncology, mental health, pregnancy and childbirth, and health promotion trials. Participants included both acceptors and decliners.	No or very minor concerns	High confidence	No or very minor concerns regarding adequacy, minor concerns regarding coherence, relevance and methodological limitations
Finding 10: HCPs in particular may influence decision making as potential participants place huge trust in them. This results in great potential for HCP influence being a key impact on decision making	Chang 2004, Canvin 2006, Harrop 2016a, Costenbader 2007, Madsen 2007b, Jackson 2010, Moynihan 2012, Smyth 2011, Habersack 2013, Gopinath 2013, Bleidorn 2015, Oud‐Rengerink 2015, Abhyankar 2016, Hughes‐Morley 2016, Bidad 2016, Ballantyne 2017, Dellson 2018	Minor concerns based on the assessment of twelve studies with no, three studies with minor and two studies with moderate methodological limitations	No or very minor concerns		Minor concerns regarding relevance as studies had moderate geographical spread Included a range of medical/surgical, oncology, mental health, and pregnancy and childbirth trials. Participants included both acceptors and decliners.	No or very minor concerns	High confidence	No or very minor concerns regarding adequacy and coherence, minor concerns regarding relevance and methodological limitations
Finding 11: Internet searching and exposure to media sources with information on trial interventions may act as either a barrier or a facilitator for trial participation	Madsen 2007a, Gopinath 2013, Habersack 2013, Bleidorn 2015, Harrop 2016a, Ballantyne 2017, de Lacey 2017,	Minor concerns based on the assessment of five studies with no, and two studies with minor methodological limitations	Moderate concerns		Moderate concerns regarding relevance as studies had limited geographical spread Included a range of medical/surgical, oncology, and pregnancy and childbirth trials. Participants included both acceptors and decliners.	Moderate concerns	Low Confidence	Minor concerns regarding and methodological limitations, moderate concerns regarding coherence, adequacy and relevance