For the fifth consecutive year, researchers worldwide have published over 4,000 scientific papers on cannabis, bringing the total number of published studies to more than 53,000, according to analysis by the non-profit advocacy group NORML.
The figures, compiled through a keyword search of the National Library of Medicine’s PubMed.gov database, reveal that 37,000 peer-reviewed papers on cannabis, its components and their mechanisms have been published since the beginning of 2015 alone.
NORML’s research also showed that of the total number of published cannabis papers, 70% were published in the past decade, and 90% of these have been published since 2022.
The available catalogue of research dates back to 1840, when William Brooke O’Shaughnessy published the first known paper on cannabis, titled “On the Preparations of the Indian Hemp, or Gunjah (Cannabis Indica), their Effects on the Animal system in Health, and their Utility in the Treatment of Tetanus and other Convulsive Diseases.”
Despite this growing body of evidence, UK cannabis patients continue to face significant barriers to accessing treatment through public healthcare. The National Institute for Health and Care Excellence (NICE) maintains the message that cannabis can’t be prescribed on the NHS because there isn’t enough clinical evidence to show that it works and that it is safe.
The guidelines for the prescription of cannabis in the UK, set by NICE, states that, “specialist doctors can prescribe cannabis-based medicinal products (CBMPs) for specific conditions like severe epilepsy, MS spasticity, and chemotherapy-induced nausea, but only after conventional treatments fail, with licensed products (like Sativex, Epidyolex) prioritized where evidence exists, and non-prescribed cannabis use advised against, emphasizing shared decision-making for unlicensed products. Prescribers must be specialists, record outcomes, and discuss risks like dependence and driving impairment with patients, as CBMPs are generally not first-line treatments.”
These guidelines haven’t changed since medical cannabis was legalised in 2018, even though there have been thousands of published papers on cannabis since this time.
Part of the reason regulators haven’t changed their stance on cannabis, despite overwhelming evidence, is due to the trust they put in randomised controlled studies (RCTs). RCTs require participants to have no knowledge of whether they are in the group which will be given the medicine to be studied or the control group given a placebo. Due to the nature of cannabis, including its smell and its effects, studying cannabis using an RCT is difficult.
Even after the law was changed in 2018, a report from NICE stated that there was inadequate evidence that cannabis is a safe and effective medicine for the treatment of certain epilepsy conditions. According to NHS data from March 2019, fewer than 10 NHS prescriptions for CBMPs had been issued in primary care since legalisation, with only five private prescriptions issued in secondary care settings. This situation has barely improved; as of 2024, the NHS issues an estimated 3-5 cannabis prescriptions per month across England.
“Despite the perception that marijuana has yet to be subject to adequate scientific scrutiny, scientists’ interest in studying cannabis has increased exponentially in the past decade, as has our understanding of the plant, its active constituents, their mechanisms of action, and their effects on both the user and upon society,” said NORML’s Deputy Director Paul Armentano.
“It is time for politicians and others to stop assessing cannabis through the lens of ‘what we don’t know’ and instead start engaging in evidence-based discussions about marijuana and marijuana reform policies that are indicative of all that we do know.”
