Table 1 Glossary of realist terms in this review

Contexts (C) – Are often ‘the ‘backdrop’ of programmes and research…broadly understood as any condition that triggers and/or modifies the behaviour of a mechanism [39].

Mechanisms (M) – are not observed directly but account for what it is about programmes that makes them work, characterised as “underlying entities, processes or structures which operate in particular contexts to generate outcomes of interest” ([40], p.368). Mechanisms are the responses of those involved in an intervention/programme to the resources or opportunities offered by that intervention/programme. Responses may include thoughts, feelings or actions. They are activated or inhibited by circumstances or contexts that then have an effect ([31], p.xvii).

Outcomes (O) – are strategies of the intervention/programme (planned or unplanned, visible or not); result of the interaction between a mechanism and its triggering context [31, 41].

Programme theories – an overarching theory or model of how a programme, or an intervention is expected to work, and it helps to explain (some of) ‘how and why, in the “real world”, a specific programme “works”, for whom, to what extent and in which contexts’ [37, 40].

Demi-regularities – a “prominent recurrent patterns of contexts and outcomes… in the data” ([33], p. 9).

Context-Mechanism-Outcome (CMO) – CMO an heuristic used to explain generative causation, which help to explain the relationship between a context, mechanism, and an outcome of interest in a particular programme [42]. It demonstrates the causal components that explain what works in an intervention/programme for who, why and in which circumstances [31].