Opinion: the lack of sufficient evidence to support medicinal cannabis products is indisputable

By Oisín Kavanagh, University of LimerickFiona Hogan, UCC and Caoimhe MurphyUCC

In 2006, US president Barack Obama revealed that he had smoked cannabis in the past with the famous line, "When I was a kid, I inhaled frequently. That was the point." In 1992, this statement would have ended the political career of Bill Clinton, who when asked the same question gave the strategic reply, "I tried it, but didn't inhale."

These quotes represent landmarks in the cultural shift towards the acceptance of cannabis as a recreational drug. This movement has reached new peaks leading to its full legalisation in certain states in the US. Cannabis and cannabis-related products are being discussed globally, with the debate making its way here. Ireland has recently allowed the use of cannabis products for specific medical conditions, but this decision is surrounded with controversy.

To understand this, we need to look at the science, or perhaps the lack thereof. Cannabis is a plant that contains more than 100 compounds called cannabinoids, two of which are of medical interest: tetrahydrocannabinol (THC) and cannabidiol (CBD). A distinction must be made between products containing THC and CBD, particularly with regards to their legal classificationTHC is the compound that is psychoactive and gives you the "high" so its supply and possession are strictly controlled by legislation. In Ireland, psychoactive cannabis is a schedule one drug, so it is considered by the State "to have strong potential for abuse and little, if any, therapeutic value." CBD, on the other hand, is not psychoactive and therefore, not regulated.

From RTÉ Radio 1's Drivetime, Jim Weathers, owner of Puff N Stuff, and Conor Gallagher, Irish Times Crime Correspondent, discuss the legal issues surrounding the sale of CBD oil

In Ireland, the debate surrounding cannabis based products began with the rise of CBD products such as oils, sprays, lotions and sweets. With this proliferation of products and increasing celebrity endorsements, it is hard to ignore the hype. However, we should acknowledge the research supporting the medical use of CBD in the treatment of severe epilepsy. It has been shown to be effective in the treatment of Dravet Syndrome where seizure occurrence has been reduced by almost 50%.

Although CBD products claim to be beneficial in the treatment of inflammation, pain, anxiety, and arthritis, this does not mean that CBD is a universal wonder drug. Research promoting its common use is inconclusive. In recent studies, CBD has failed to decrease symptoms of experimentally induced anxiety, chronic pain following kidney transplantation and ulcerative colitis. Yet, consumers are bombarded with advertising of CBD's health claims without sufficient supporting evidence. Selling these products without evidence to support these claims could be seen as unethical (at best).

Efficacy aside, can CBD oil cause harm? According to a recent British Medical Journal article, patients should be advised that "CBD products lack quality assurance and should not be treated as medicines." In the EU, the levels of the psychoactive THC cannot exceed 0.2% in non-medicinal CBD products. But the lack of regulation, quality assurance checks and standardisation when it is sold as a food supplement begs the question regarding the safety of its contents. A study conducted in the Netherlands on 46 cannabis oil products showed that many products contained significantly varying levels of cannabinoids than claimed on the label, with seven samples containing no CBD or THC at all.

From RTÉ Radio 1's Today with Sean O'Rourke, a discussion about Ireland's medical cannabis access programme

That being said, when it comes to medicinal cannabis (with high THC content i.e. psychoactive), there is some evidence supporting its use. Limited research confirms treatment benefits for three conditions, namely rigidity associated with multiple sclerosis, uncontrollable nausea and vomiting associated with chemotherapy and severe, treatment-resistant epilepsy. Only these conditions are permitted to be treated legally with medicinal cannabis in Ireland and other uses are currently illegal.

Emerging evidence also indicates that cannabis has analgesic effects in both neuropathic and non-neuropathic painbut Irish clinicians cannot prescribe medical cannabis for these conditions. Worryingly, some research has illustrated that cannabis with high THC content may trigger psychosis in vulnerable individuals. Further, early or heavy cannabis use has been linked to an increased risk of schizophrenia in adulthood.

Clearly, there is conflicting evidence surrounding cannabis and its' chemical derivatives. However, the future of cannabis research may not be so ambiguous with the recent launch of  Project Twenty21 that aims to create Europe's largest single body of evidence supporting the efficacy of medical cannabis in various conditions.

A RTÉ Brainstorm video on the 200 year history of Ireland and medicinal cannabis

Despite the current lack of research and the potential risk to health, there is clear public demand for a legally accessible supply chain of medical cannabis. Globally many people rely on medical cannabis but in Ireland it is not readily available as it is considered a treatment of last resort. Additionally, due to its negative image, some clinicians may be hesitant to prescribe it. As a result, some medical cannabis users turn to the black market for their supply. This is an obvious risk as they are completely unaware of the contents of the cannabis and that the profits could be used to fund other criminal enterprises.

With regards to the status of cannabis in Ireland, the regulatory body that approves new medicines, HPRA notes that the government's decision "to permit access to cannabis for medical use is a societal and policy decision due to the paucity of scientific research, the recreational use of the product and the strong public and patient demand." This level of evidence would not be adequate to allow the release of a new pharmaceutical drug to the market.

It is impossible to ignore the common thread in many research papers. The lack of sufficient evidence to support the use of medicinal cannabis products is indisputable. The current promotion of these products with false claims is wrong and unethical. Nonetheless, these products are indispensable in some people's lives and further research is urgently required to keep up with this fast growing movement. Hopefully, initiatives such as Project Twenty21 will lead the way. However, if the scientific evidence does not support the use of cannabis as a medicine, it must be removed from the market.

Oisín Kavanagh is a pharmacist and PhD researcher with SSPC, the SFI Research Centre for Pharmaceuticals, at the Bernal institute within the University of LimerickFiona Hogan is a UCC pharmacy student currently undertaking a research placement in the Bernal Institute at the University of LimerickCaoimhe Murphy is a UCC pharmacy student currently undertaking a research placement in the Bernal Institute at the University of Limerick.


The views expressed here are those of the author and do not represent or reflect the views of RTÉ