While many articles and studies have supported the therapeutic use of cannabidiol (CBD), several have disclosed funding from CBD-related parties, raising concerns about publication bias and the potential of a coordinated industry effort to increase the volume of pro-CBD literature, according to analysis results published in the Annals of Internal Medicine.
Researchers from Yale University examined articles, editorial pieces, reviews, and commentaries on the characteristics, use, or therapeutic value of CBD, all of which were published in English. Studies published between 2017 and 2019 that included animal models, human participants, or laboratory measures were included. In their review of these articles, the researchers recorded whether each article reported a CBD-related source of industry funding, disclosed conflicts of interest, or had author affiliations with the CBD industry.
A total of 417 articles were included in the review. Approximately 48% of these were animal or basic science studies; 28.3% were nonsystematic reviews, editorials, or commentaries; and 23.7% were human studies. There were 86 articles (20.6%) that disclosed CBD-related industry funding. Of these, 50% received financial support from the same organization. In addition, 28.5% and 15.6% of articles reported CBD-related conflicts of interest and authors who were employed by a CBD company, respectively.
The bulk of the literature analyzed by the researchers contained 149 articles (35.7%) that had any CBD-related conflict of interest, with 61.6% of human studies reporting CBD-related conflicts of interest. The majority of articles (65.7%) supported CBD in their conclusion sections, with only 7% reporting unsupportive conclusions. Supportive conclusions were found in 79.1% of articles with CBD-related industry funding compared with 62.2% of articles without industry funding. In addition, 73.8% of articles with supportive conclusions had CBD-related funding, CBD-related conflict of interest disclosure, or authors who were employed by the CBD industry.
Study limitations were the inclusion of only articles from MEDLINE, the possibility of unreported funding and conflict of interest disclosure statements in the assessed articles, as well as the lack of adjustment for different articles that were authored by the same group of people.
The investigators wrote that potential industry bias and “conflicts should be taken into account when the legitimacy of health-related claims from CBD studies is evaluated.”
Deary EC, Ross JS, Nyhan K, Wallach JD. Conflicts of interest among authors of published cannabidiol articles, 2014-2019 [published online March 17, 2020]. Ann Intern Med. doi:10.7326/M19-3650