Grey Literature is a Necessary Facet in a Critical Approach to Gambling Research

Commercial gambling has seen massive global expansion in the past 25 years. It is a huge industry selling a risky form of entertainment: problem gambling is the only non- substance addiction recognized in the DSM-5, affecting an average of 2.3% of people in jurisdictions where prevalence data are available. Gambling also harms people who gamble below the clinical threshold of "problem gambling", as well as the friends, families and communities of people who gamble. Gambling harm is disproportionally felt by racialized peoples and people of lower socioeconomic status. As such, researchers and governments are increasingly viewing gambling as a public health issue. Gambling research is published in both the primary and grey literature, and the integrity of gambling research is a topic of increasingly heated debate. Bibliometric reviews have found that gambling research is heavily focused on the psychological and biological characteristics of people with problem gambling, with less emphasis on the gambling products themselves and how they are provided. While the gambling grey literature is recognized as valuable by the gambling research community, it has not yet been systematically assessed. In this paper we present the grey literature analysis portion of a pilot project to use a big data approach to produce a mapping review of gambling research from five nations: Australia, Canada, New Zealand, United Kingdom, and United States. For primary research publications on gambling, we performed systematized searches on the Scopus and Web of Science databases. For gambling grey literature, we retrieved all grey literature documents in the GREO International Gambling Research Evidence Centre. For the period of 2014-2018, the grey literature search yielded 360 reports, compared to 1292 articles in the primary literature search.