Of nine systematic reviews on cannabis use disorder treatments, 78% had at least one author with a conflict of interest, but no significant relationship was found between conflicts of interest and favorability of results or conclusions.
Researchers, clinicians, journal editors, and anyone evaluating the quality of cannabis treatment evidence.
78% of CUD treatment reviews had authors with conflicts of interest
What the researchers found
77.8% (7/9) of systematic reviews had at least one author with a COI. Of 51 authors, 29.4% had COIs. 44% of reviews received funding, 22% were unfunded, and 33% had no funding statement. Despite COIs, there was no significant association between funding source and results (p=0.429) or between COI presence and favorability of results (p=0.56).
Why it matters
With cannabis use disorder treatment becoming more important as legalization expands, understanding whether the evidence base is influenced by conflicts of interest is crucial for clinical decision-making.
The numbers in context
9 systematic reviews; 51 authors; 78% of reviews had ≥1 author with COI; 29.4% of authors had COIs; no significant bias in results (p=0.56) or conclusions.
How the study worked
Cross-sectional study searching Ovid MEDLINE and Embase for systematic reviews and meta-analyses on CUD treatment. Nine eligible reviews with 51 authors were evaluated for disclosed and undisclosed conflicts of interest using a standardized classification scheme.
What this study cannot tell us
Very small sample (only 9 systematic reviews). Limited statistical power to detect bias. Cannot detect subtle forms of bias. COI classification may not capture all potential conflicts. Only examined systematic reviews, not primary studies.
How to read the evidence
Systematic meta-research approach, but very small sample of only nine reviews limits conclusions.
When this study was published
Published in 2022 with searches through June 2020.
The bigger picture
While the high prevalence of COIs in cannabis research mirrors patterns seen across biomedical research, the absence of significant bias in this small sample is somewhat reassuring, though stricter disclosure guidelines are still warranted.
Questions still open
- Would a larger sample reveal hidden bias? Are there subtler ways COIs influence cannabis research beyond results and conclusions (e.g., choice of outcomes, framing)? Should funding sources be more transparently reported?
Common questions
Is cannabis treatment research biased by industry funding?
What types of conflicts of interest were found?
Read the original research
Evaluating the relationship between industry sponsorship and conflicts of interest among systematic review authors on treatments for cannabis use disorder.
Substance abuse, 43(1), 1180-1189
Citation
Carr, Marvin; Reddy, Vaishnavi; Anderson, J Michael; Weaver, Michael; Hartwell, Micah; Vassar, Matt. (2022). Evaluating the relationship between industry sponsorship and conflicts of interest among systematic review authors on treatments for cannabis use disorder.. Substance abuse, 43(1), 1180-1189. https://doi.org/10.1080/08897077.2022.2074598
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