Evidence synthesis grounded in theory or conceptual frameworks provide the most robust results. Utilising theories and frameworks serve several purposes, which also slightly differ depending on the type of review undertaken.
Using theory in evidence synthesis can be a two-way street whereby theory can inform the conduct of an evidence synthesis (including the selection of studies and extraction, synthesis and interpretation of data), and engaging critically with one or more frameworks can shed light onto the frameworks themselves, which can spur further theoretical development.
Social theories
In qualitative reviews, social theories can underpin the approach. These theories can influence and improve the review process, from shaping initial review questions, to criteria for including reports, to coding and synthesising data. Theory can also be used to guide and ground interpretation of the findings.
Theories like feminism, critical theory, or intersectionality help researchers interpret data in a way that considers power relations, social constructs, and inequalities. It also allows researchers to critically compare where existing literature diverges or aligns with theory, thus informing and guiding further research based on underlying concepts and driving forces.
Framework for implementation science and practice-orientated questions
In evidence synthesis related to implementation science and practice-oriented questions, Theories of Change (ToCs), Programme Impact Pathways (PIPs) or logic models may be particularly important to guide the methodology and synthesis strategy, as well as to relate findings to what was ‘expected’ based on conceptualization, i.e. to see how pathways to impact played out as planned, or failed to do so.
These conceptual frameworks are especially useful in evidence synthesis on implementation questions because they are meant to represent either substantiated or hypothesis-driven ‘building blocks’ of impact, which should be generalizable, and thus inform efforts at scale.
Conceptual frameworks
Conceptual frameworks, especially important for mapping evidence and framework synthesis, function to ground findings within the wider body of literature, and justify recommendations for future inquiry.
For instance, when discussing nutrition topics, using internationally established frameworks such as UNICEF's Conceptual Framework on the Determinants of Maternal and Child Nutrition can be used to predefine the thematic categories for organising studies, but also help to compare and map how and to what degree literature has substantiated the theoretical pathways to impact.