. 2021 Jul 21;11(7):e050632. doi: 10.1136/bmjopen-2021-050632

Table 1.

Key concepts

Concept	Definition
Critical realism	A philosophical framework that combines positivist (the paradigm underpinning natural sciences) and interpretivist (a paradigm that emphasises experiences and interpretations over the ‘objective’ truth assumed by positivism) understanding of the world.⁶⁵ Of particular relevance to realist research is the concept of ontological depth,⁴⁹ depicting a stratified reality with three layers: the empirical (things and events that are observed); the actual (things that exist and events that occur but are not observed); and the real (mechanisms that are not directly observable but can potentially cause events to occur).^{43 62 65}
Scientific realism	An approach to theory development and testing that draws on critical realism, and makes use of realist concepts and methods, such as retroduction.⁴⁵ This is the original framework underpinning realist evaluation and reviews,^{45 66} but applications of scientific realism and interpretations of the relationship between scientific and critical realism are varied and contested in the field of realist evaluation.⁵¹
Realist review	A theory-driven and iterative approach to reviewing and synthesising literature in order to provide an explanation of how, why, for whom and under what circumstances programmes, policies and interventions work or do not work.^{47 48}
Programme theory	Theories that link activities and outcomes to explain how and why a change is expected to take place, representing how the mechanisms introduced into pre-existing contexts can generate outcomes.^{48 67}
Context (C)	The conditions (eg, individual, organisational and environmental features), historical elements or relational and dynamic features that can potentially (dis)activate existing or introduced mechanisms.^{48 49 68} This is not the same as ‘setting’ or ‘context’ in a generic sense of providing background information, and only captures those aspects of the context that have a bearing on mechanisms and outcomes.
Mechanism (M)	An underlying entity that produces specific outcomes in specific contexts. Mechanisms are a combination of resources (eg, components of an intervention) and responses (eg, the perceptions of participants) highlighting the importance of examining how interventions are received as opposed to merely considering how they are intended.^{48 49}
Outcome (O)	Expected or actual change achieved by the combination of specific contexts and mechanisms.^{48 49}
Context–mechanism–outcome (CMO) configuration	CMO configurations are representations of a causal relationship between contexts and mechanisms that lead to specific outcomes.^{49 50}
Community engagement in research	A strategy for building and maintaining relationships between researchers and the communities the research concerns, or who are intended to benefit from interventions or research findings.²
Participatory research	A research approach that involves research participants at different stages of the research process, for example, study design, planning and analysis, rather than merely as informants or recipients of an intervention. Many different methods, such as visual participatory analysis, exist under this general approach.³⁶
Health promotion	Health promotion refers to actions and processes that create better conditions for health through, for example, strengthening people’s control over their own health and addressing societal determinants of ill-health.³⁰
Abductive thinking	A form of inventive and intuitive (‘hunch-driven’) thinking that allows a researcher to creatively imagine, for example, potential mechanisms to be investigated.^{45 69}
Retroduction	Theorising and testing of hidden causal mechanisms that have, for example, been imagined through abductive thinking or inductively inferred from descriptions of existing studies.^{45 49 69}
Counterfactual thinking	The consideration and application of contradictory evidence or alternative explanations to an interpretation, such as a CMO configuration, to further test and refine it.^{48 70}