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Unlocking the Potential: UK’s Evolving Landscape of Medical Cannabis Research

Written for Business of Cannabis by Releaf. 

The UK moved to legalise medical cannabis in 2018, but while the market has grown rapidly over the last five years, seeing the UK become the second largest market in Europe, barriers remain that continue to prevent the industry from reaching its full potential.

According to research conducted by Releaf, one of the newest and most innovative UK-based medical cannabis clinics, 50% of the UK’s population (roughly 29.6m people) currently have a condition that could make them eligible for a medical cannabis prescription. The clinic’s doctors can prescribe cannabis-based medicines for a wide range of conditions, and patients can check their eligibility for medical cannabis treatment for free via the clinic’s website.

One issue repeatedly cited by clinicians and medical professionals as a barrier to expanding prescriptions is the lack of clinical research conducted on cannabis.

However, as we’ll explore in this article, there is a wealth of activity in the UK and beyond which could soon make that a thing of the past.

An overview of global research on cannabinoids

The volume of cannabis research has skyrocketed over the last two decades. According to US-based advocacy organisation, NORML, over 32,000 peer-reviewed papers specific to cannabis have been published since 2010, with the annual number increasing year-on-year.

In a 2018 study which explored the trends in cannabis-related publications, investigators reported that the total number of peer-reviewed publications dedicated to medical cannabis has increased ninefold since the year 2000.

This trend was echoed in a paper published last year by the US Food and Drug Administration, which reported that around 400 new investigational drug applications for cannabis-derived products had been submitted in the last decade — the same as in the 40 years prior combined.

Although the majority of clinical trials on cannabinoids in the last decade have been registered in the US, the UK is now fast becoming a leader in the field.

Recent research from Prohibition Partners suggests that the UK saw the second highest number of trials registered via clinicaltrials.gov, making up 13% of all trials during the last 13 years.

Randomised Control Trials (RCTs)

Randomised controlled trials (RCTs) are typically referred to as the pinnacle of scientific evidence in clinical research. These trials are essential for securing licensing approval from regulatory bodies like the MHRA.

In RCTs, participants are randomly assigned to different groups to evaluate the efficacy of a specific drug, treatment, or intervention. One group receives the intervention, while the other, known as the control group, either receives a placebo or no treatment at all. Researchers then monitor both groups over time, measuring outcomes at predetermined intervals and analysing any differences statistically.

However, conducting RCTs on cannabis presents unique challenges. These trials are typically designed for single compound pharmaceuticals, whereas cannabis contains numerous cannabinoids, terpenes, and flavonoids—over 144 cannabinoids alone.

Some experts argue that the ‘entourage effect,’ the combined action of these compounds, plays a critical role in the therapeutic effects of medical cannabis, potentially yielding stronger effects than individual compounds. However, replicating this synergy in an RCT setting poses significant challenges.

Clinical Trials in the UK

Five years after the legalisation of medical cannabis in the UK, the National Institute for Health Research (NIHR) has revealed that no government-funded clinical trials on cannabinoids have been approved so far.

Two RCTs examining the effects of CBD and CBD:THC in childhood epilepsy are, however, said to be ‘under operational consideration’.

Despite the lack of government-funded trials, various private organisations have taken steps to advance the evidence base. These organisations have obtained regulatory approval for conducting trials using cannabis-based products to address various medical conditions.

Let’s explore some of the research and conditions that have already been registered in the UK.


  • Glioblastoma: ARISTOCRAT is recruiting patients for a phase 2 trial comparing Sativex with placebo in recurrent glioblastoma patients, alongside temozolomide chemotherapy.
  • Long Covid: A recent phase 2 trial assessed CBD-dominant medicinal cannabis for managing Long Covid symptoms, finding it safe and well-tolerated.
  • Chronic Pain: The CANPAIN study examines the safety and efficacy of inhaled cannabis flower for chronic pain, with plans for a larger study involving 5,000 participants.
  • ADHD: A pilot study explored Sativex in adults with ADHD, showing preliminary evidence supporting cannabis use for symptom management.
  • Spasticity, Neuropathy, and Cancer Pain: Several trials investigate Sativex for spasticity and pain in MS, diabetic neuropathy, spinal cord injury, and advanced cancer pain.
  • Cannabis and Harm Reduction: Trials explore recreational cannabis use, optimal CBD-THC doses, effects in schizophrenia patients, and CBD’s potential for treating cannabis use disorder.
  • Upcoming Trials: Future research areas include chemotherapy-induced neuropathy, endometriosis pain, and novel cannabinoid therapies targeting inflammation, cancer, and various types of pain, such as pancreatic ductal adenocarcinoma and acute/post-surgical pain.


Alongside these clinical trials, the UK has a significant and ever-expanding database of real-world evidence collected through schemes such as T21 (formerly Project Twenty21) led by Drug Science, and the UK Medical Cannabis Patient Registry.

This research also supports the use of cannabis in treating a wide range of chronic conditions, including ADHD, anxiety, autism spectrum disorder (ASD), depression, epilepsy, Fibromyalgia, insomnia, IBD and PTSD.

More research is needed

There’s growing interest in exploring the therapeutic potential of cannabinoids, although the evidence is still emerging. Studies suggest cannabinoids could be beneficial for treating challenging conditions like spasticity, neuropathy, and chronic pain, where current treatments often fall short.

Many patients who find relief from cannabis have struggled with conventional therapies. For them, cannabis offers hope and a chance to improve their quality of life.

However, more research, especially randomised controlled trials (RCTs), is needed in the UK to expand access to medical cannabis treatments. Government-funded trials and data collection through the NHS Patient Registry are crucial steps to enhance our understanding of medical cannabis’s safety and effectiveness and guide future clinical studies.


Releaf is one of the newest clinics offering medical cannabis in the UK, and plans to help build the pool of real world evidence by analysing and publishing patient data in the future.

For more information on this research and further educational resources, visit Releaf’s Education page or contact a member of their team.

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