Measuring What Matters

Outcomes will decide future of cannabis medicine.

The UK medical cannabis sector has spent seven years arguing for access. The next argument will be settled on outcomes, and judging by the evidence available right now, the industry is not equipped to win it.

The Lancet Psychiatry‘s systematic review of cannabinoids, published on 16 March, concluded that the available randomized controlled trial evidence does not justify the routine prescribing of medical cannabis for mental health disorders.

Following its publication, the industry has been the target of a relentless media campaign, calling for tighter regulation, increased prescription oversight, and an overarching rethink of the entire sector.

According to recent figures from NHSBSA FOI data, the number of private prescriptions more than doubled from 283,000 in 2023 to around 659,000 in 2024.

UK prescriptions have scaled far faster than the clinical evidence base could match. Clinics that focus on keeping meticulous, credible, longitudinal patient data stand at a significant advantage.

Not only do they have a solid evidence base to defend their prescriptions against such scrutiny, but have the opportunity to build a wider, more substantial case for the benefits so many of their patients experience with treatment.

The evidence the trials cannot reach

One of the key studies referenced in the Lancet study was the Wilson review, which screened 5,774 studies and included 54 randomized controlled trials covering 2,477 participants.

It found no significant benefit for anxiety, PTSD, psychotic disorders, OCD, anorexia or opioid use disorder, and no eligible trials at all for depression.

Evidence certainty was rated very low or low under the GRADE framework, as Business of Cannabis reported at the time of publication.

The review does not conclude that cannabinoids don’t work, but that the controlled evidence base is too thin to support routine prescribing at scale, and that the conditions driving prescription growth are precisely those for which trial evidence is weakest.

Dr Anne Schlag of Drug Science, which operates the UK’s largest non-profit medical cannabis registry, has argued that the patients most likely to seek a prescription are typically multi-morbid, sometimes carrying up to ten concurrent diagnoses, and would be excluded from RCT cohorts.

The registry, now following more than 4,500 patients for up to five years, finds significant symptom reduction at three months in those with comorbid depression and PTSD.

Uncontrolled data cannot, on its own, establish whether a treatment works. The patients’ UK clinics treat patients outside the RCT base, and finding a solution to this dynamic is now the critical problem for the industry to solve.

What 1,669 patients told one clinic

In November 2025, Releaf, a CQC-regulated medical cannabis clinic and one of the UK’s largest, surveyed its active patient base.

Of 1,669 respondents, 672 reported being prescribed for anxiety, depression, PTSD or a combination of the three. Participation was voluntary and uncompensated.

Writing in Releaf’s own blog, Sam North said the survey returned ‘a very consistent signal across all three conditions’.

Among the mental health cohort, 80% rated their treatment very or extremely effective and 94% reported at least moderate effectiveness.

Meanwhile, fewer than 4% reported limited or no effect. Improved quality of life was reported by 98%, improved daily functioning by 87%, and improved capacity for work or study by just under 70%. PTSD respondents reported the strongest overall response.

Survey data of this kind cannot do what an RCT does, the respondent pool is self-selecting and paying privately. Outcomes are self-reported, and there is no control arm.

Releaf’s findings sit broadly in line with two recent peer-reviewed cohorts. A two-year case series of 698 depression patients drawn from the UK Medical Cannabis Registry, published in the Journal of Affective Disorders, found significant reductions in depression severity at one, three, six, 12 and 24 months.

A December 2025 prospective cohort also found that patients above clinical thresholds fell from 81% (anxiety) and 76% (depression) at baseline to below 50% within three months.

The data that the system cannot see

In October 2025, Business of Cannabis analyzed NHSBSA records covering more than 132,000 prescription entries. The agency confirmed that private cannabis prescriptions are ‘manually recorded from often handwritten prescriptions’ with ‘no standardized naming convention’.

Product match rates fell as low as 77.5% for 2022, meaning nearly one in four prescription records that year could not be reliably assigned to a specific medicine.

That same fractured dataset underpins the figures now driving mainstream coverage. The Times‘ April investigation, which claimed ten doctors issued more than half of all UK cannabis prescriptions since 2019, drew on a bespoke FOI response that has not been published in full.

Business of Cannabis has requested this same data, and will report it publicly once it has been received.

This data issue cuts both ways. Critics work from a dataset that cannot reliably account for what each clinic does, and operators defend themselves without the outcomes record that would settle the question.

Oliver’s Law, launched by Oliver Robinson’s family, calls for a central NHS registry recording every prescription issued, alongside routine CQC inspections and published prescribing data.

Many in the industry have argued for the same architecture for years. The reform climate has made it close to inevitable. The question is whether the registry is designed collaboratively, with the operators that hold the patient relationships, or imposed by a regulator working without them.

The next test

The CQC and MHRA already have the powers required to implement these changes and establish a sector-wide requirement to capture and publish standardised outcome measures, using validated instruments, at agreed follow-up intervals.

Such a mandate would supply the longitudinal evidence the trial pathway cannot generate at scale, give regulators a defensible mechanism for distinguishing well-run clinics from poorly run ones, and give the sector the response it currently lacks when challenged on safety, scale or efficacy.

Whether a top-down mandated change is pushed through by regulators first, or whether the industry itself pulls together to produce a coordinated industry standard, those who are already building this evidence base will have a seat at the table whenever change is made.

This is Third-Party content and does not reflect (or not not reflect) the views of Cannabis Confidential or CB1 Capital.