It is a catch-all term for material published non-commercially such as by government agencies, industry bodies, NGO's or academic institutions. It includes:
Grey literature is frequently high quality and up to date information. In some areas it may be the only information available. However it is not peer reviewed and should be evaluated with this in mind.
There is no central database for grey literature such as Medline or Embase. Instead searches will need to target multiple sources. The following resources can help:
EuropePMC is an open science platform that searches multiple sources including many preprint servers.
Filter for preprints using the left hand sidebar.
WHO's Clinical Trials Search Portal aggregates results from multiple trial registries.
Trip database is a search engine for biomedical and health material. Once searched look at the right hand sidebar to restrict results to guidelines, regulatory materials, blogs etc.
NICE Evidence Search is run by the UK's National Health Service. It includes evidence summaries, patient information, material from professional bodies and more.
Google Advanced Search. Use advanced search to restrict to particular domains eg .gov.au or file types eg .pdf.
Using Google for domain searching can be helpful if a sites internal searching capability is poor. Eg adding 'site:www.medrxiv.org' to a Google search will search within the MedRxiv site. More information on our Google for research guide.
OAIster searches institutional repositories and digital libraries.
Grey Matters includes an extensive list of national and international HTA web sites, drug and device regulatory agencies, clinical trial registries, health economics resources and drug formulary web sites. It is produced by the Canadian Agency for Drugs and Technologies in Health.
Analysis & Policy Observatory (APO) collects grey literature on many public policy areas, including health, from government, agencies, regulators, research institutes, non-for-profits and think tanks. Australian focused.
Most grey literature sources do not have the functionality of databases. This can make it hard to manage recording searches and collecting references.
Be aware that search engines can return different results over time and location, reducing transparency and replicability. Recording your activity mitigates this.