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Controversies in Medical Cannabis

Scientist holding Cannabis plant


Anne Katrin Schlag, Saoirse E. O’Sullivan, Rayyan R. Zafar, David J.Nutt


May 18, 2021

Knowledge about the therapeutic potential of medical cannabis has greatly improved over the past decade, with an ever-increasing range of developments in human clinical applications. A growing body of scientific evidence supports the use of medical cannabis products for some therapeutic indications, but for others, the evidence base remains disputed.

One reason for this is the relative lack of randomised controlled trials (RCTs) of medical cannabis treatment. While RCTs have long been seen as the gold standard of research, it is important to understand that results from RCTs do not always translate to real-world therapeutic use.

This is particularly true with medical cannabis patients, where many suffer from multiple pathologies which would exclude them from an RCT, thus making it difficult to predict their health outcomes from RCT results alone. This is why real-world studies such as Project Twenty21 are so important.

Furthermore, the strongest empirical data supports the use of cannabis-based medicinal products for conditions with relatively small patient numbers. Yet the conditions where the highest patient numbers present, often have debatable clinical evidence but good real-world evidence, incorporating patient-reported outcomes of thousands of patients.

Chart on the relative number of patients

To highlight this issue, this narrative review provides a summary of the various medical conditions for which medical cannabis is a potential treatment.

This includes indications with substantial evidence, such as intractable childhood epilepsy and multiple sclerosis, as well as areas where the evidence is still controversial, such as PTSD and anxiety.

We provide a high-level summary of current developments using findings from recent major reviews, as well as real-world evidence, including global database registries and other patient-reported outcomes.

For open-access to the full report of this research, see below:

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