Background

\label{background}
Wikipedia is a free-content online encyclopaedia containing articles on a vast range of topics. The name itself is a portmanteau of an Hawaiian language word “wiki” meaning quick, and the word encyclopaedia \cite{WikipediaA_Wikipedia}. At present there are over 40 million articles with 5.3m in the English language \cite{Wikipedia_Wikipediaa}. Since its creation in 2001, Wikipedia has expanded to attract over 374 million unique visitors each month. This made Wikipedia the 5th most popular site on the internet in 2017 \cite{Alexa_Alexa}.
Wikipedia is openly-editable. This means that any one of these users can access and edit the majority of articles. Wikipedia policy states, however, that all information presented in pages must be “verifiable against a published reliable source” \cite{Wikipedia_Wikipedia}. Therefore, all pages contain references for the information they provide. To prevent the risk of pages being “vandalised” with misinformation Wikipedia has various quality control measures. These include; a “watchlist” to notify editors when a page has been edited, a published list of recent changes that editors can access to review, automated computer scripts, page protection on more controversial pages, edit filters on certain pages and blocking any editors who repeatedly vandalise pages \cite{Heilman_2011}. On top of this, Wikipedia has a team of administrators. They are editors who have been given access to additional tools on their account. These include the ability to block/unblock accounts, edit fully protected pages and delete/undelete pages. There are 1,291 administrators on the English language Wikipedia as of August 2016 \cite{Wikipediab:Administrators_Wikipedia}.
Wikipedia contains many pages relating to healthcare. In 2014 the English language version was estimated to contain 25,000 articles on health-related topics, while across all languages there are 155,000 articles containing 950,000 references \cite{WikipediaHealth_Wikipedia}. These are often accessed via search engine results with one survey suggesting that around 22% of healthcare-related online searches direct to Wikipedia pages \cite{Laurent_2009}\cite{Makovsky_Makovsky}. In 2013 health pages on Wikipedia received 4.8 billion views, making it one of the most used means for accessing health information globally \cite{Heilman_2015}. When use of Wikipedia is studied in medical students and doctors, it is clear that it is becoming an increasingly popular resource \cite{Hughes_2009,Hughes_2009a}. This is, perhaps, enhanced by Wikipedia being entirely free of charge – including data download charges in low and middle income countries. In this context there is criticism that as Wikipedia is openly editable and that the information may be unreliable. Some evidence suggests, however, that there is no difference in accuracy when Wikipedia is compared to other professionally maintained medical databases \cite{Rajagopalan_2011} although opinions differ by subspecialty, depending on the ‘target’ readership and across time (Table 1).
The Cochrane Collaboration is a non-for profit NGO producing, and maintaining systematic reviews of health care. A systematic review “attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. It uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made” \cite{CochraneHandbook_Cochrane}. Cochrane Reviews are published in the Cochrane Database of Systematic Reviews; one of the databases included in the Cochrane Library, published by Wiley. Full access to the Cochrane Library is available to several countries where a national provision has been purchased and freely available to over 120 low and middle-income countries; it is also sold via a subscription model to institutional and individual users \cite{CochraneLibrary_Cochrane}. An additional ‘entry point’ to each review is the plain language summary (PLS) on the Cochrane Library. This award-winning section aims to make the information more accessible to people without specialist knowledge \cite{CochraneStandards_Cochrane} and is accompanied by a more traditional academic abstract of the review and a hyperlink to the full publication. The Collaboration is made up of subgroups and Cochrane Schizophrenia produce and update high quality systematic reviews and meta-analyses relevant to people with schizophrenia and related psychotic conditions.
In 2004 a group called WikiProject Medicine was started with the aim of creating and managing medical articles on Wikipedia. This group allows discussion and collaboration on these articles to improve the quality of the information presented \cite{Heilman_2011}. In 2014 a formalised partnership between Wikipedia and Cochrane was formed, aiming to “transform the quality and content of health evidence available online” \cite{WikipediaxCochrane_Wikipedia}. This involves incorporating Cochrane’s evidence into Wikipedia articles improving the information’s accuracy and reliability. Whilst increasing accessibility of highest grade maintained health care information seems a laudable aim objective quantification of the effects of this effort is unknown.

Preliminary work

\label{preliminary-work}
Stability of intervention: One possible problem with quantification of the effects of reporting and referencing evidence in Wikipedia pages is that the pages are open to editing. The evidence, and reference to that evidence could be deleted. In anticipation of this trial, in 2014 we seeded four Wikipedia pages with pilot tables and a reference to the source Cochrane review (e.g. \cite{Chlorpromazine_Wikipedia}). The pages were chosen to represent one old drug that is not widely recommended, one old drug that is on the WHO Essential drug list, one new drug that is not off patent, and one psychological intervention that has generated much interest for people with schizophrenia. The evidence tables – and source references - within these reviews have remained stable.
Proportion eligible: Cochrane Schizophrenia produces and maintains over 200 reviews but it was unclear for what proportion of those reviews a relevant Wikipedia page already existed. For example, a Wikipedia page detailing an overview of treatment for people with schizophrenia would be too general for any one Cochrane review as these tend to be focused on named treatments. However, the Wikipedia page on ‘Chlorpromazine’ would be entirely relevant to one or more Cochrane reviews because chlorpromazine is a drug often used for the care of people with schizophrenia. In 2016 we investigated this issue and found that around half (97) of Cochrane Schizophrenia reviews had an obvious ‘landing’ page directly addressing the issue of the review \cite{CochraneProportion_Cochrane} (Table 2).