Library Guides: Cardiorespiratory Sciences: Using Grey Literature

What is Grey Literature?

The term grey literature is used to describe a wide range of different information that is produced outside of traditional publishing and distribution channels, and which is often not well represented in indexing databases.

Grey literature can be described in many ways, but the most widely accepted definition was adopted in 1997 and expanded in 2004 at the Grey Literature Conference in Luxembourg and New York City, respectively. This definition states that grey literature is "information produced on all levels of government, academia, business and industry in electronic and print formats not controlled by commercial publishing, i.e. where publishing is the not the primary activity of the producing body" (Mering, 2018). Due to its often informal nature, grey literature is seldom subjected to a peer review process, and as such can vary widely in quality.

Grey literature:

Is not widely disseminated
Can be difficult to find
May contain more information as they lack publication length stipulations
Can be produced and disseminated much faster than published literature
Is less expensive to access than traditional closed-access literature
May not be subject to rigorous peer review process
Is often not archived

Mering, M. (2018). Defining and understanding grey literature. Serials Review, 44(3), 238–240. https://doi.org/10.1080/00987913.2018.1525239

Why Use Grey Literature?

For systematic and scoping reviews, a grey literature search may be mandatory or strongly recommended. The guidelines you are using for your review (such as Campbell, JBI, Cochrane, CEE) may recommend or require that you search for grey literature resources, including:

Reports (eg from government, non-profits, associations)
Dissertations or theses
Conference abstracts
Clinical trials registry records (for health reviews)
Technical reports
Patents

Published journals may be susceptible to biases against reporting negative or neutral outcomes, a phenomenon known as "positive result bias." Including grey literature or cross-referencing published studies with their grey literature counterparts (e.g. study protocols, clinical trials) can help combat various publication biases.

For other research projects, grey literature may be:

More current, with better coverage of emergent research areas
A better source of information on policies and programs
A source of more diverse perspectives than mainstream publications offer
More detailed than journal articles, with raw data or more extensive context
More widely accessible by you and your potential audience

Pros and Cons of Using Grey Literature

Uniqueness and Currency v Quality and Longevity

Grey Literature can be a very important research resource.

It can record findings in niche or emerging research areas and also record research findings that produce null or negative results. These may not be addressed by the commercial publishers - who may have a more mainstream, profit based publishing strategy.
It may be more current than formally published research literature which can take time to pass through a sometimes lengthy peer review and editorial publishing process.
It can connect you with content from a more diverse range of authors and institutions. Not everyone is able to publish through commercial publication routes

You should be aware of the need to assess and capture potentially useful resources

Grey Literature sources can vary hugely in terms of quality.
Scholarly publications such as books and journals pass through a formal publishing process and are subject to in depth editing review. In many cases there is a peer review process where draft versions are subject to a scrutiny process by a panel of experts. Papers may be modified and improved in light of the expert feedback before reaching final published status.
Not all grey literature material is subject to a similarly rigorous pre publication review process, so you should exercise caution and make your own assessment for quality, reliability and potential bias. Some reports however, do undergo rigorous expert review so check each source to see what it says about a review process.
Grey literature is often not formally published. For example, a report may be posted to a government website or a poster presentation may be given at a conference. In these cases you need to consider the longevity of the resource. Something may be available on the web, or a blog for a short period only and may not be formally archived.
Make sure you keep a record of material you wish to use/reference - as it may not be there for discovery later down the line.