Background: An increasing number of systematic reviews (SRs) have been conducted to map, synthesize, and critically evaluate clinical trials on the effects of cannabis derivatives and their synthetic analogues for different health conditions. The process of searching for studies impacts the reliability of the SRs. It is important to understand how this process has been conducted to guide the planning of SRs and to support further strategies for continuous enhancement of methodological recommendations.
Objectives: To assess the methodological and reporting quality of search strategies used by SRs to identify randomized clinical trials about therapeutical use of cannabis derivatives and their synthetic analogues.
Methods: Meta-epidemiological study conducted in the Discipline of Evidence-Based Medicine, Escola Paulista de Medicina, Unifesp, Brazil and supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico through an academic scholarship (CNPq, number 134763/2021-1). Two authors independently investigated the use of Peer Review of Electronic Search Strategies (PRESS) and Preferred Reporting Items for Systematic reviews and Meta-Analyses literature search extension (PRISMA-S) checklists by the SRs included and, additionally, the adequacy of A MeaSurement Tool to Assess systematic Reviews (AMSTAR)-2 item related to search process (item 4).
Results: We identified 86 SRs on the topic, published in MEDLINE from January 1, 2019, to September 21, 2021. None of them referred to the use of PRESS for constructing the searches, nor to the PRISMA-S checklist for reporting them. Regarding the AMSTAR-2 item 4, 89.53% (n=77) SRs searched on at least two relevant databases, 32.56% (n=28) used Medical Subject Headings (MeSH) terms properly, and all respected a limit of 1 year between the search date and the SR publication, but only 1.1% (n=1) of SRs presented a justification for the use of filters and limits.
Conclusions: PRESS and PRISMA-S checklists have been poorly adopted by SRs on the cannabis therapy field. Some of the components of AMSTAR-2 item 4 are not fully covered as well. Patient, public, and/or healthcare consumer involvement: By revealing the low adherence to methodological and reporting tools, this study alerts us to the risk of bias in the process of conducting and reporting the clinical effects of cannabinoids, which may limit the applicability of its conclusions or even mislead the body of evidence supporting decision-making.