Materials and procedure
The project idea and research plans including draft focus group materials were presented at two separate PPI (Patient and Public Involvement) group meetings of the “Leicester, Leicestershire and Rutland Ageing Patient and Public Involvement Forum” and the “Ethnic Minority Research Inclusion (EMRI) Hub (South Yorkshire)” prior to data collection. Overall, PPI group members were supportive of the research ideas, but highlighted a number of potential limitations and practical barriers to clinical placebo use, which were considered by the research team and implemented in the study materials. One PPI group suggestion included asking focus groups about the acceptability of charging patients for placebo prescriptions. A separate question on this topic was included in the topic guide.Four virtual focus groups were conducted 2–4 November 2022 and lasted 30–70 min. Group sizes depended on participant availability and turn-up rates. Groups 1–4 comprised four, three, two and seven participants, respectively. All participants were recruited through an advertisement on social media. Prior to participation, they completed a consent form and a pre-study questionnaire including demographic items and basic questions about existing knowledge or previous experiences with placebos. According to this questionnaire, all participants had a personal working definition of placebos, but no participant was an expert in the topic (e.g. a medical prescriber or researcher in the field). All focus groups were conducted by the same researcher (EMK), following the same semi-structured topic guide (see Additional File 