What is grey literature?

Grey literature refers to materials and research outputs not formally published or distributed by commercial publishers. These documents are typically produced by organisations such as governments, academic institutions, or nonprofits and can include a variety of formats, such as:

• Reports (e.g., technical reports, government or organisational publications)
• Dissertations and theses
• White papers and working papers
• Datasets
• Standards and guidelines

Grey literature is often not peer-reviewed and can be harder to locate compared to traditional, published literature. 

Do I need to search grey literature?

Grey literature is important because it broadens the scope of research by including unpublished or non-traditional studies, which can significantly impact findings and reduce publication bias, particularly in systematic reviews.

Additionally, grey literature can often provide more current information and raw data.

Many authoritative sources advocate for its inclusion in research to enhance rigor and accuracy, including:

• Cochrane Handbook for Systematic Reviews of Interventions
• The U.S. Agency for Healthcare Research and Quality
• The Australian Commission on Safety and Quality in Health Care (ACSQHC)