The exponential increase in medical cannabis-related studies, with more than 20,000 peer-reviewed articles (using the single keyword “marijuana”) published in the last five years alone, underscores the need for sophisticated tools to manage this wealth of information.
Given this substantial and rapidly expanding understanding of the endocannabinoid system (ECS) and research focusing on cannabinoid-based therapeutics, it is clear that clinicians require reliable resources to navigate this complex and ever-evolving scientific landscape.
Several scientific repositories are available to learn more about this emerging field in medicine. Here, we examine and contrast five: Pubmed, PubMed Central, ResearchGate, CannaKeys, and Cochrane Library.
For a side-by-side comparison, see the chart at the end of the article.
PubMed and PubMed Central
PubMed (1997) and PubMed Central (2000) are compiled and maintained by the US National Library of Medicine at the National Institutes of Health (NIH). Public access to PubMed is free and to date (March 10, 2024), it contained 9,775 results1 associated with the search words “medicinal cannabis” spanning a period between 1840 and today. PubMed includes the abstracts of most studies from the 1950s, while Pubmed Central (PMC) provides the full text of each paper published but is limited to mostly more recent trials. PMC contained 42,829 results2 associated with the search words “medicinal cannabis,” spanning between 1799 and today. However, upon closer examination, you’ll quickly notice many false positives, i.e., listing studies unrelated to the search terms, which explains the large discrepancy between the two sites.* This is one of the critical drawbacks of PMC. In contrast, PubMed is more focused and accurate when associating your queries. Clinically relevant filter options for both are limited to include type of study, date of publication, and, in the case of PMC, source of funding, for example. Neither PubMed nor PMC provide context about the use of cannabinoid-based therapeutics in general or in the clinical setting specifically.
ResearchGate
ResearchGate is a European social media site (2008) for researchers and scientists that is an interesting blend of a scientific repository and social networking. Depending on whether it is in the public domain, RG may carry the abstract or full text. One of its strengths lies in the ease with which you can reach out to the authors of a particular study and ask specific questions. While it is still up to each scientist to respond, I had good results reaching out to several of them, allowing for a lively exchange of information. Metadata regarding the total number of cannabis studies is not available. As such, RG does not provide any broader context about using cannabinoid-based therapeutics in the clinical setting.
CannaKeys
CannaKeys (CK) is a California, Berkeley-based (2019) online repository and App that offers a suite of features. All studies entered into the platform are related to the medicinal use of cannabis constituents and the endocannabinoid health sciences. With an average of 300 new trials added every quarter, the current total (March 2024) is more than 7,000 studies. CK aggregates and synthesizes the latest research and presents a dashboard that provides an in-depth breakdown of studies, including their relevance, importance, and clinical implications. The CK dashboard also distinguishes between primary and related trials, saving clinicians valuable time by letting you know, at a glance, which trials are focused directly or more peripherally on a particular disease, thus providing a more focused context. CK enables you to filter for over 150 ECS-related data points that have potential relevance in the clinical setting, allowing clinicians to make more informed and discerning decisions to optimize patient outcomes. Unlike the other repositories, CK provides a synopsis based on all included endocannabinoid system (ECS) related studies, providing an overview or state of the science regarding each condition for which the use of cannabinoid-based therapeutics shows degrees of efficacy. CK also tracks, includes, and summarizes studies focused on crucial endo-, phyto-, and synthetic cannabinoids, terpenes, organ systems, and modulators of the endocannabinoidome (eCBome).
Cochrane Library
Cochrane Library (1993) is a British online repository published by John Wiley & Sons, Inc. It conducts systematic reviews of clinical trials utilizing the volunteer work of thousands of international experts. Its strength lies in that it publishes the highest level of evidence-based trials regarding the use of cannabis as medicine. Some of the information is free, others behind a paywall. Cochrane provides some context about using cannabinoid-based therapeutics in the clinical setting. Criticism about the publications centers on a significantly high number of inconclusive findings (contrary to other systematic reviews),3 slow updates of reviews when new data has become available,4 and too stringent attrition/exclusion criteria.5
In summary, the rapid growth of medical cannabis-related research underscores the necessity for practical tools to manage this wealth of information. The availability of scientific repositories like Pubmed, PubMed Central, ResearchGate, CannaKeys, and Cochrane Library offers various options for accessing information in this emerging field of medicine. However, choosing the most suitable resource depends on individual needs, time, and effort available for acquiring knowledge in endocannabinoid medicine.
Each repository has strengths and limitations in providing context about using cannabinoid-based therapeutics in the clinical setting. While PubMed and PubMed Central offer access to many studies, PMC may contain false positives and have limited filter options. ResearchGate allows interaction with study authors but lacks metadata on the number of cannabis studies and clinical context. CannaKeys provides a comprehensive overview of trials and filters for clinical relevance, making it valuable for healthcare professionals, some of which are free while others lie behind their subscription paywall. Cochrane Library publishes high-quality, evidence-based trials but has been criticized for the high rate of study exclusion, inconclusive findings, and slow updates.
Ultimately, choosing the best-suited resource depends on the specific needs, time, and energy available for acquiring knowledge in endocannabinoid medicine. The following charts provide you with a brief overview that makes it easier to compare their offerings.
A Side-by-side Comparison
| Options Overview | PM | PMC | RG | CK | C |
| # of studies using keyword “medicinal cannabis” (3/24) | 9.8K | 42.8K* | N/A | 7.3K | 284 |
| Abstract (if in public domain) | ✔ | ✔ | ✔ | ✔ | ✔ |
| Full text (if in public domain) | ✔ | ✔ | ✔ | ||
| Current data | ✔ | ✔ | ✔ | ✔ | |
| Access to summary dashboard data | ✔ | ||||
| Research dashboard with dynamic data visualization tools | ✔ | ||||
| Filter by type of study, country, year | ✔ | ✔ | ✔ | ✔ | ✔ |
| Condition-specific synopsis based on all included endocannabinoid system (ECS) related studies | ✔ | ||||
| ECS-related filters | ✔ | ||||
| Number of ECS-related data points you can filter for | – | – | – | 154 | – |
| List of all condition for which cannabis shows degrees of efficacy | ✔ | ||||
| ICD-10 code | ✔ | ||||
| Access to treatment algorithms | ✔ | ||||
| Filter option to determine positive, negative, or mixed study outcomes | ✔ | ||||
| Table of condition-specific dosing data | ✔ | ||||
| Filter for specific dosing data | ✔ |
Endnotes:
1. https://pubmed.ncbi.nlm.nih.gov/?term=medicinal+cannabis
2. https://www.ncbi.nlm.nih.gov/pmc
3. Tricco AC, Tetzlaff J, Pham B, Brehaut J, Moher D. Non-Cochrane vs. Cochrane reviews were twice as likely to have positive conclusion statements: cross-sectional study. J Clin Epidemiol. 2009 Apr;62(4):380-386.e1.
4. Green-Hennessy S. Cochrane systematic reviews for the mental health field: is the gold standard tarnished? Psychiatr Serv. 2013 Jan;64(1):65-70.
5. Hutton P, Morrison AP, Yung AR, Taylor PJ, French P, Dunn G. Effects of drop-out on efficacy estimates in five Cochrane reviews of popular antipsychotics for schizophrenia. Acta Psychiatr Scand. 2012 Jul;126(1):1-11.
