Developing a theory of change - the importance of rich process data and authors' insights into context, implementation and mechanisms.

Background: Theories of change explaining how interventions work are increasingly important, yet the methods/data to develop these are less advanced than for evaluating effects.

Methods: We conducted a systematic evidence synthesis to develop a theory of change for structural adolescent contraception interventions. We reflect on the utility of the information provided in evaluation reports.

Findings/discussion: Few of the included evaluations presented their theory of change, or included rich, qualitative process data. Authors' descriptions of context and implementation, typically in introduction and discussion sections, were very useful. These helped to understand the intervention's context, how it was experienced and why or how it had the effect that it did. We recommend incorporating rich process evaluations into studies, and reporting contextual insights into the intervention's development, implementation and experience. We also recommend including these data and insights within syntheses that aim to develop theories of change.