From substance to process: A meta-ethnographic review of how healthcare professionals and patients understand placebos and their effects in primary care.

Research suggests that a 'placebo' can improve conditions common in primary care including pain, depression and irritable bowel syndrome. However, disagreement persists over the definition and clinical relevance of placebo treatments. We conducted a meta-ethnographic, mixed-research systematic review to explore how healthcare professionals and patients understand placebos and their effects in primary care. We conducted systematic literature searches of five databases - augmented by reference chaining, key author searches and expert opinion - related to views on placebos, placebo effects and placebo use in primary care. From a total of 34 eligible quantitative, qualitative and mixed-methods articles reporting findings from 28 studies, 21 were related to healthcare professionals' views, 11 were related to patients' views and two were related to both groups. In the studies under review, healthcare professionals reported using placebos at markedly different frequencies. This was highly influenced by how placebos were defined in the studies. Both healthcare professionals and patients predominantly defined placebos as material substances such as 'inert' pills, despite this definition being inconsistent with current scientific thinking. However, healthcare professionals also, but less prevalently, defined placebos in a different way: as contextual processes. This better concurs with modern placebo definitions, which focus on context, ritual, meaning and enactivism. However, given the enduring ubiquity of substance definitions, for both healthcare professionals and patients, we question the practical, clinical validity of stretching the term 'placebo' towards its modern iteration. To produce 'placebo effects', therefore, primary healthcare professionals may be better off abandoning placebo terminology altogether.