Challenges to evaluating complex interventions: a content analysis of published papers

BACKGROUND: There is continuing interest among practitioners, policymakers and researchers in the evaluation of complex interventions stemming from the need to further develop the evidence base on the effectiveness of healthcare and public health interventions, and an awareness that evaluation becomes more challenging if interventions are complex.We undertook an analysis of published journal articles in order to identify aspects of complexity described by writers, the fields in which complex interventions are being evaluated and the challenges experienced in design, implementation and evaluation. This paper outlines the findings of this documentary analysis. METHODS: The PubMed electronic database was searched for the ten year period, January 2002 to December 2011, using the term "complex intervention*" in the title and/or abstract of a paper. We extracted text from papers to a table and carried out a thematic analysis to identify authors' descriptions of challenges faced in developing, implementing and evaluating complex interventions. RESULTS: The search resulted in a sample of 221 papers of which full text of 216 was obtained and 207 were included in the analysis. The 207 papers broadly cover clinical, public health and methodological topics. Challenges described included the content and standardisation of interventions, the impact of the people involved (staff and patients), the organisational context of implementation, the development of outcome measures, and evaluation. CONCLUSIONS: Our analysis of these papers suggests that more detailed reporting of information on outcomes, context and intervention is required for complex interventions. Future revisions to reporting guidelines for both primary and secondary research may need to take aspects of complexity into account to enhance their value to both researchers and users of research.