Evidence Synthesis and Systematic Reviews

Grey literature can be broadly defined as everything but peer reviewed journals and academically or commercially published books. Examples of grey literature include, but are not limited to: discussion papers, data sets, clinical trials, dissertations/theses, government documents, reports, brochures, leaflets, and fact sheets. 

Source: Bonato, S. (2018). Searching the grey literature: A handbook for searching reports, working papers, and other unpublished research. Rowman & Littlefield. 

Evidence Synthesis reviews aim to identify and analyze all the relevant information to have the most complete picture of the available evidence. It is imperative to have a wide-reaching pool of available research to analyze, this means including grey literature to make your search as comprehensive as possible. Here are 10 reasons why grey literature is a valuable source of information to include in your evidence synthesis review:

1. Grey literature provides a unique global perspective.
2. There may be a lack of or very little information available in published literature.
3. Grey literature is a source for evidence-based practice publications.
4. Grey literature sources can complement sources located in published literature. 
5. Grey literature sources may provide a more detailed information picture.
6. Grey literature publications can be accessible and relevant to a wider range of readers.
7. Grey literature can be the most current source of information.
8. Grey literature is a major source of knowledge dissemination.
9. Grey literature offers diverse sources of information.
10. Grey literature is, more often than not, free.

Source: Bonato, S. (2018). Searching the grey literature: A handbook for searching reports, working papers, and other unpublished research. Rowman & Littlefield.