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The Evidence-Based Medicine (EBM) movement endorses a hierarchy of evidence that places randomized controlled trials at the top. More specifically, double-blind, placebo- controlled trials are often considered to be the 'best of the best'. This view leads to the paradox that treatments that seem to be most strongly supported by evidence, ranging from tracheotomies to rabies vaccines, have never been tested in randomized trials of any description and are hence supported by (allegedly) sub-optimal evidence. Moreover many of these treatments do not seem supportable by best evidence - how, for example do we keep the surgeons who perform tracheotomies 'blind'. After a brief introduction (chapter 1), and review of the literature (chapter 2), I argue that criticisms of the EBM hierarchy can be launched from the simple basis that best evidence rules out the most plausible rival hypothesis (chapter 3). To examine the relative evidential weight of placebo controlled trials compared to 'active' controlled trials (in which the control treatment is an existing established treatment) requires a good deal of conceptual work. I defend a modified version of Grunbaum's (1981/1986) definition of placebos (chapter 4), then provide constraints on what can count as a 'legitimate' placebo control (chapter 5). Next, I explain why double-blinding does not always rule out additional rival hypotheses. I then argue that the arguments for the superiority of placebo controls are flawed. The 'assay sensitivity' argument is limited in scope and based on a misconception about the nature of placebo controls (chapter 7), while the claim that only placebo controlled trials measure the absolute effect size relies on the questionable assumption that placebo and non-placebo effects add rather than interact (chapter 8). I conclude that the evidence hierarchy endorsed by EBM does not stand on solid foundations.

Mindfulness-based programs (MBPs) are increasingly offered in the workplace to reduce stress and enhance wellbeing. A growing body of evidence suggests that these programmes can be beneficial; however, dropout rates are often high, and there is great heterogeneity in both programme content and strength of effects between studies. This thesis contributes to a better understanding of what makes these programmes successful, under what circumstances, for whom, and why. A realist approach was employed that is theory-driven and well-suited to make sense of complex interventions, such as MBPs. First, I conducted a realist review where I analysed and synthesised data from 75 existing studies of workplace MBPs to identify the mechanisms through which these programmes work or do not work and discover how particular contexts impact these mechanisms and, consequently, outcomes. The findings were consolidated into a programme theory augmented by theories from organisational literature, such as conservation of resources (COR) theory and psychological safety. I then tested and refined parts of that programme theory with realist evaluation methodology. The evaluation consisted of five workplace MBPs and included quantitative and qualitative data collection methods. The research results show that for managers and employees to invest in an MBP and benefit from it, it is crucial that they feel safe to engage with selfcare at work and show vulnerability to each other. The more participants feel that they are not at work, the safer they feel. To be beneficial, it is also important that managers and employees link the programme and its activities to existing goals and practices. If these conditions are not met, the costs of investing in an MBP may be too high and lead to the strategic use of brief mindfulness exercises, non-adherence, or dropout. These findings should be of value to decision makers and practitioners wishing to offer and implement effective and sustainable workplace MBPs.

Background Participatory trials conducted over the internet are growing in scope with minimal guidance for Patient and Public Involvement (PPI). Replication and the use of trial findings in decision-making may depend on the methods used to conduct and report these trials. Aim To assess which research methods might be adapted to improve the conduct and degree of patient and public co-production within trials and in the work leading up to them. Methods A mixed-methods participatory action approach was used which included a blend of different studies, as noted under Findings. Findings Overall, I have shown why and how research teams struggle with building protocols for online trials and the design, conduct, and reporting of public involvement in trials generally and specifically in online trials. They express conflict about where and how to report PPI succinctly without interfering with reporting and research discussion. For instance, my systematic overview provides background from existing research on PPI in clinical trials' design generally and my thematic analysis of social media comments about clinical trials found PPI increases the quantity and quality of patient-relevant priorities and outcomes, enrolment, funding, design, implementation and dissemination and yet roles and research boundaries were not clearly understood. An assessment of reporting quality and the methods used for self-recruited online trials of self-management health interventions, which I augmented with a survey of authors of online trials reporting quality found methods were poorly reported and seldom replicable. While a series of analyses on the use of public involvement statements in The BMJ, and surveys on supplementary materials, data sharing and dissemination found that simply requiring reporting of these areas increased the quantity and then quality. Finally, an online Delphi identified a consensus about what to include in the protocol for a participatory online trial. Conclusions This thesis demonstrates co-production with the public across multiple research designs with minimal funding is possible and improves research. Guidance for protocols and reporting methods in participatory online trials was identified as beneficial by stakeholders. The post-thesis development of a multi-use online trial participatory protocol template, online training and the research reporting guideline is underwritten by Stanford University.