Financial conflicts common among authors of CBD studies, suggesting potential for bias

Many studies that evaluate the use, therapeutic effects and characteristics of cannabidiol, or CBD, are produced by authors with conflicts of interest that tie them to the industry and potentially lead to bias, according to research published in the Annals of Internal Medicine.

“Over the past few years, there has been growing interest in the potential health benefits of CBD,” Joshua D. Wallach, MS, PhD, an assistant professor of epidemiology at Yale School of Public Health, told Healio Primary Care. “Considering the worldwide growth in the CBD market, as well as the number of companies invested in the commercial success of CBD, it is important to be aware of the potential role that the CBD industry may be having on research that is being disseminated to the public.”

Currently, the FDA has approved only one drug derived from CBD, Epidolex (cannabidiol, GW Research Ltd.), to treat seizures in people with rare forms of epilepsy.

Wallach and colleagues searched online databases for research articles, editorials, commentaries and reviews published between January 2014 and July 2019 that evaluated the characteristics, use and therapeutic effects of CBD. Once identified, the researchers recorded characteristics of the study; CBD-related funding source; conflicts of interest; author affiliations; and whether the conclusions were supportive, neutral or unsupportive of CBD.

They identified 417 articles, 99 (23.7%) of which were human studies. Among all articles, 20.6% disclosed funding from a CBD-related industry, and 50% of those received funding from the same company.

Wallach and colleagues found that 28.5% of all articles had authors who reported CBD-related industry funding, and 15.6% had authors who were employed in the CBD industry.

Of the human studies, 61.6% included reports of CBD-related conflicts of interest.

Among all articles, 65.7% had findings supportive of CBD and 7% had unsupportive findings. When examining the types of studies, researchers determined that 71.7% of human studies and 65.5% of animal and scientific studies had positive results.

Nearly 80% of studies with funding from CBD-related industries had CBD-supportive results compared with 62.2% of studies that did not have CBD-related funding, according to the researchers. In addition, 73.8% of studies with CBD-related funding, authors with CBD-related conflicts of interest or authors employed by CBD-related industries had CBD-supportive results compared with 61.2% of studies that did not have those conflicts.

“Given the potential for industry bias, our study suggests the need to critically evaluate where research is coming from when assessing the findings supporting various CBD-health-related claims,” Wallach said.

He explained the study does not suggest that certain researchers should or should not work on studies involving CBD, but “additional evidence from nonconflicted sources may help clarify uncertainties and reveal whether there are potential publication and industry biases.” – by Erin Michael

Disclosures: Wallach reports receiving support through the Collaboration for Research Integrity and Transparency from the Laura and John Arnold Foundation and through the Yale-Mayo Clinical Center for Excellence in Regulatory Science and Innovation in the last 36 months. Please see the study for all other authors’ relevant financial disclosures.