Key issues in clinical and epidemiological research in complementary and alternative medicine - a systematic literature review

Background: In the last 2 decades there has been a large increase in publications on complementary and alternative medicine (CAM). However, CAM research methodology was heterogeneous and often of low quality. The aim of this systematic review was to investigate scientific publications with regards to general issues, concepts and strategies. We also looked at research priorities and methods employed to evaluate the clinical and epidemiological research of CAM in the past to identify the basis for consensus-based research strategies. Methods: We performed a systematic literature search for papers published between 1990 and 2010 in 7 electronic databases (Medline, Web of Science, PsychArticles, PsycInfo, CINAHL, EMBASE and Cochrane Library) on December 16 and 17, 2010. In addition, experts were asked to nominate relevant papers. Inclusion criteria were publications dealing with research methodology, priorities or complexities in the scientific evaluation of CAM. All references were assessed in a multistage process to identify relevant papers. Results: From the 3,279 references derived from the search and 98 references contributed by CAM experts, 170 papers fulfilled the criteria and were included in the analysis. The following key issues were identified: difficulties in past CAM research (e.g., randomisation, blinding), utility of quantitative and qualitative research methods in CAM, priority setting in CAM research and specific issues regarding various CAM modalities. Conclusions: Most authors vote for the use of commonly accepted research methods to evaluate CAM. There was broad consensus that a mixed methods approach is the most suitable for gathering conclusive knowledge about CAM.