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Federal report: Evidence lacking on effectiveness of cannabis for IBS
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Evidence on the effectiveness of cannabis and cannabinoids for the treatment of irritable bowel syndrome is insufficient, and represents a significant research gap that should be addressed by diverse stakeholders, according to a new report from the National Academies of Sciences, Engineering, and Medicine released yesterday.
The Committee on the Health Effects of Marijuana performed a comprehensive review of research on the therapeutic and health effects of cannabis and cannabis-related products published since 1999, considering more than 10,000 abstracts to inform nearly 100 conclusions drawn in the report.
“For years the landscape of marijuana use has been rapidly shifting as more and more states are legalizing cannabis for the treatment of medical conditions and recreational use,” Marie McCormick, MD, ScD, chair of the committee; the Sumner and Esther Feldberg Professor of Maternal and Child Health, department of social and behavioral sciences, Harvard T.H. Chan School of Public Health; and professor of pediatrics, Harvard Medical School, Cambridge, Mass., said in a press release. “This growing acceptance, accessibility, and use of cannabis and its derivatives have raised important public health concerns. Moreover, the lack of any aggregated knowledge of cannabis-related health effects has led to uncertainty about what, if any, are the harms or benefits from its use. We conducted an in-depth and broad review of the most recent research to establish firmly what the science says and to highlight areas that still need further examination. As laws and policies continue to change, research must also.”
Cannabinoids do demonstrate potential therapeutic effects in IBS, according to the report. Studies have shown that the colonic mucosa and neuromuscular layers contain cannabinoid type 1 (CB1) receptors, and these are also expressed in plasma cells, which influence mucosal inflammation. In addition, animal studies have shown endocannabinoids that act on CB1 receptors result in the inhibition of gastric and small intestinal transit and colonic motility, and a randomized controlled trial demonstrated effects on gastric and colonic motility in healthy volunteers.
However, the committee was unable to identify a systematic review of sufficient quality that reported on the effectiveness of medical cannabis for treating IBS symptoms.
They did identify a randomized controlled trial evaluating dronabinol — a cannabinoid medication used to treat chemotherapy-induced nausea and vomiting and loss of appetite or weight loss in patients with AIDs — in patients with diarrhea-predominant irritable bowel syndrome. In it, researchers randomly assigned 36 adult patients to receive two different doses of dronabinol or placebo for 2 days, and observed no treatment effects on gastric, small bowel or colonic transit measured by radioscintigraphy.
“The quality of evidence for the finding of no effect for irritable bowel syndrome is insufficient based on the short treatment duration, small sample size, short-term follow-up, and lack of patient-reported outcomes,” the committee wrote. “Trials that evaluate the effects of cannabinoids on patient-reported outcomes are needed to further understand the clinical effects in patients with IBS.”
Thus, they were unable to conclude whether dronabinol is effective for the treatment of IBS.
Similarly, the committee was unable to draw conclusions about the association between cannabis use and the risk for certain cancers, including gastrointestinal cancers, due to insufficient evidence.
However, the committee did conclude there is conclusive or substantial evidence that cannabis or cannabinoids are effective for treating chronic pain in adults, chemotherapy-induced nausea or vomiting, and for improving symptoms of multiple sclerosis.
The committee identified the therapeutic effects of cannabis on IBS symptoms as a significant research gap, and developed four recommendations to address this and other research gaps, calling for adequate public and private funding and support for these studies; research standards set by the U.S. Department of Health and Human Services; federal and state public health surveillance efforts; and a federally supported committee to develop strategies for overcoming cannabis research barriers. Such research barriers emphasized in the report include the Schedule I classification of cannabis, and the lack of access to cannabis products for research. – by Adam Leitenberger
Reference:
National Academies of Sciences, Engineering, and Medicine. 2017. The health effects of cannabis and cannabinoids: The current state of evidence and recommendations for research. Washington, DC: The National Academies Press. doi:10.17226/24625.
Disclosures: Healio Gastroenterology was unable to confirm the committee members’ relevant financial disclosures at the time of publication.
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Mark Gerich, MD
This is a rigorous and broad report on the health effects of cannabis and cannabinoids. It is not entirely comprehensive, however, since the search strategy was predefined to focus on specific therapeutic areas of interest. IBD was not included in this search and, for that reason, it was not commented upon in the study. The authors do not explain their rationale for not including IBD (or other excluded disease states) in their search strategy; however, one might guess that it is related to their areas of expertise and their opinion that there was unlikely to be high quality data in the literature about the clinical effectiveness of cannabis or cannabinoids for IBD, which is unfortunately true.
Of note, as part of their section on immunity and infectious disease, the authors did review three good quality studies about the association between cannabis use and health outcomes among individuals infected with viral hepatitis C. These studies had mixed results regarding cannabis use and liver disease progression. Overall, their conclusion was that the existing evidence, albeit limited, against an association between cannabis use and the progression of liver fibrosis and hepatic disease in individuals with HCV was stronger than the evidence that there is an association.
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