In 2018, the legalization of medical cannabis in the UK marked a pivotal change, driven by campaigns advocating for children with treatment-resistant epilepsy.
The legal reforms permit specialist medical consultants to prescribe cannabis-based medical products (CBPMs) for a variety of conditions, always prioritizing the patient’s well-being.
Despite this legalization, the possession and use of cannabis (classified as a class B drug) without a valid prescription continues to be illegal in the UK.
Most cannabis products available are unlicensed, lacking endorsement from the Medicines and Healthcare products Regulatory Agency (MHRA), resulting in limited prescriptions through the National Health Service (NHS). This gap has inadvertently triggered a burgeoning private market.
Currently, more than 30 specialist cannabis clinics are registered with the Healthcare Quality Commission, with estimated prescriptions for cannabis products reaching 80,000 patients. Conditions treated range from chronic pain and anxiety to ADHD.
Data reveals that 42% of patients were prescribed medical cannabis for mental health issues such as anxiety, depression, PTSD, and OCD, aligning with trends observed in Australia and the US.
However, a recent review published in Lancet Psychiatry assessed over 50 randomized controlled trials (RCTs) and found “no evidence” supporting the efficacy of cannabinoids for treating conditions like anxiety, PTSD, substance use disorders, ADHD, bipolar disorder, psychotic disorders, or anorexia.
While some efficacy was noted for cannabis use disorder, insomnia, Tourette syndrome, and autism spectrum disorder, these findings were categorized as “low quality.”
The Advisory Committee on the Abuse of Drugs (ACMD) is conducting a review examining the implications of medical cannabis prescriptions in the UK, focusing on any “unintended consequences” resulting from recent legal changes.
Professor Owen Bowden Jones, former ACMD Chairman, indicated that the study results indicate that the benefits of medical cannabis may have been “overestimated” for numerous conditions, and these products “should not be administered for psychiatric conditions lacking supportive evidence.”
“We must focus on reducing barriers to facilitate superior research that further explores cannabis product effects,” he added.
The review asserts that routine cannabinoid use for mental health conditions is “seldom justified,” raising critical questions, notably, why is cannabis prescribed despite limited evidence of its effectiveness?
Treatment Options
It is stated that “absence of evidence is not evidence of absence.” Dr. Niraj Singh, a consultant psychiatrist in the UK, has prescribed medical cannabis for over six years.
“Numerous patients have reported that this treatment effectively addresses a range of conditions, and most use it responsibly. In my experience, it has yielded positive results, enabling patients to lead happy, fulfilling lives,” Singh remarked.
Many patients seeking treatment at cannabis clinics have reportedly exhausted all traditional options or lack access to adequate mental health support. As of January 2026, 1.5 million adults engaged with NHS mental health services, while 8.7 million people were prescribed antidepressants in the UK from 2023 to 2024, believed to be effective for approximately one year.
In a survey by the United Patient Alliance, a patient dealing with anxiety, depression, and PTSD expressed feeling “seen and supported” after receiving effective treatment without harmful side effects associated with previous prescriptions.
“In instances where individuals have plateaued in treatment options, medical cannabis is making a significant difference,” Singh expressed.
Evidence from peer-reviewed studies links cannabis to improved symptoms and quality of life for conditions such as: PTSD, OCD, and insomnia. However, observational studies were excluded from the aforementioned review due to concerns of biases that could not establish causality.
Despite the need for more robust clinical trials, Professor David Nutt, former chair of ACMD and founder of the independent charity Drug Science, argues that RCTs alone do not offer sufficient data on a drug’s effectiveness.
This sentiment is echoed by Sir Michael Rollins, former director of the MHRA and the National Institute for Healthcare Research and Evaluation (NICE). He emphasized the need for real-world evidence that could yield “better clinical data and statistical power” in a speech at the Royal College of Physicians.
According to Nutt, “Placebo-controlled trials are costly and involve highly selective patient populations, limiting their generalizability.” He also highlighted that cannabis’s numerous active compounds, which vary vastly in dosage and formulation, pose significant challenges when conducting double-blind, placebo-controlled studies. Professor Mike Burns, President of the Association of Medical Cannabis Clinicians, emphasized the need for a more nuanced approach in understanding mental health prescribing.
Clinical Supervision
Medical cannabis can induce side effects, including heightened anxiety and paranoia, making it unsuitable for individuals with a history of psychosis.
According to a survey published in BMJ Mental Health, those using cannabis for self-medication tend to use it more frequently and consume higher levels of tetrahydrocannabinol (THC), resulting in increased paranoia.
“Cannabis is not devoid of side effects,” stated Dr. Marta Di Forti, a Professor of Drug Use, Genetics, and Psychosis at King’s College London, who runs a clinic for individuals with mental health issues in London.
She recounted cases where patients developed complications after being prescribed products containing high THC levels, leading to hospitalizations for psychotic symptoms. Yet, much of our understanding in this area remains anecdotal.
“There is valid reasoning for prescribing cannabis as medication,” she noted. “However, there must be comprehensive evidence and proper oversight, which is currently lacking.”
The Association of Medical Cannabis Clinicians recommends a review by a peer panel for prescriptions exceeding 60 grams per month or containing over 25% THC. Like other controlled substances, prescribing CBPM requires diligent clinical oversight, thorough evaluation, and ongoing monitoring, especially in complex cases with significant mental health histories.
While Singh noted that side effects are relatively rare, he expressed concern about the rising availability of high-THC products. “Checks and balances are imperative,” he insisted, “as adjustments to THC concentrations must be carefully monitored.”
Prescribers maintain that a strong clinical oversight process is in place, stating they’ve never felt pressure to prescribe. Eligibility for medical cannabis entails having undergone at least two previous treatments, receiving an evaluation from a psychiatrist, and being reviewed by a multidisciplinary team.
Nonetheless, some critics argue that clinics should enhance support and training for prescribers and have a responsibility to foster research that substantiates their claims. “The industry has not adequately collected and analyzed patient outcomes,” Burns stated. “Clinics have a moral obligation to gather and share data whenever possible.”
Evidence Gap
There is a shared consensus on the urgent need to develop a robust evidence base. However, finding common ground proves challenging. Some advocate for cannabis’s efficacy, while others dispute it, with a lack of substantial research to confirm either stance.
Nutt emphasized that the current clinical research system is inadequate for medical cannabis. “In 2018, the Health Ministry pledged to conduct efficacy trials for children with epilepsy, but no progress has been made. This reflects a disinterest from pharmaceutical companies due to the impossibility of patenting plant medicines.”
This challenge cannot be solved solely by a call for further research, he noted, but requires prioritizing real-world data and practical experience to support cannabis in clinical settings.
Meanwhile, patients express fears of being pushed back into the illegal market, where they have no access to medical oversight or regulated products, which is widely viewed as more dangerous.
Denying access to medical marijuana based on “incomplete evidence” not only misrepresents scientific data but also inflicts harm on patients who rely on it, according to the United Patient Alliance.
“Real-world evidence studies, patient-reported outcomes, and research focusing on treatment-resistant populations are critically needed,” they added. “We do not ask for science to be ignored; we urge it to catch up with patient experiences.”
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Source: www.sciencefocus.com
