Lancet Psychiatry Review on Cannabinoids for Mental Disorders: Thin Evidence or Convenient Hit Piece?
Article Written by Adam Isaac Miller
Read time: 2-3 mins
A new systematic review claims scant support for cannabinoids in treating anxiety, depression and other mental health conditions – but a closer look reveals a paper that says more about research gaps than the plant itself.
I must admit, upon reading this latest Lancet Psychiatry systematic review and meta-analysis, my initial response was a familiar mix of frustration and disbelief. Titled “The efficacy and safety of cannabinoids for the treatment of mental disorders and substance use disorders,” the paper concludes there is “a crucial need for more high-quality research” and that “the routine use of cannabinoids for the treatment of mental disorders and SUDs is currently rarely justified.”
Sounds damning, right? Except when you pull it apart – as Pharmacist Matt has already done so brilliantly – what emerges is not evidence of inefficacy, but a textbook case of how strict RCT-only inclusion criteria, tiny sample sizes and methodological choices can dress up a research-gap paper as an inefficacy paper.
For context, medicinal cannabis prescribing in Australia has now surpassed one million approvals under the SAS-B scheme. Yet this review drops at a time when the AMA and Pharmacy Guild are still pushing back on broader access. Convenient timing indeed.
The Numbers Don’t Lie – and They’re Tiny
Matt’s breakdown is spot on. Across all mental disorders and substance use disorders, the review found just 54 RCTs involving a grand total of 2,477 participants. That’s it – after 45 years of data.
For anxiety: only 6 studies (352 participants total). Matt counted 4 with 293 patients – either way, it’s embarrassingly small.
For depression: zero RCTs existed to review. None. Zilch.
All cannabinoids were lumped together – CBD, THC, synthetics, isolates – as if they were one single drug. Real-world prescribing, where we titrate doses, adjust ratios and use whole-plant or balanced formulations? Not represented here.
What They Included – and What They Left Out
The authors set an extremely high bar for inclusion: only RCTs, no observational data. Several trials showing benefit (including work from Johns Hopkins researchers) were excluded because they didn’t meet the rigorous entry standard.
As Matt pointed out to me, “It’s nearly impossible to properly blind THC. Patients know when they’re getting it.” That alone inflates the placebo response and undermines the entire RCT framework for psychoactive medicines.
Then there’s the dosing issue. Every trial used fixed doses of single-molecule pharmaceutical cannabinoids – dronabinol (synthetic Δ9-THC), nabilone (synthetic THC analogue) or pharmaceutical-grade CBD isolate (like Epidiolex).
Would we accept a meta-analysis of “antidepressants” that pooled lithium, mirtazapine and fluoxetine at fixed doses in capsules and concluded the entire class doesn’t work? Of course not. Yet that’s exactly the standard applied here to cannabis.
You don’t start a patient on a high fixed dose of THC in real life – you start low and go slow, titrate, find the therapeutic window. These trials were almost designed to fail at reflecting clinical practice.
Author Conflicts and the Bigger Picture
One of the authors, Wayne Hall, has previously received payment for expert testimony on the risks of cannabis use and is well known in some circles as an “anti-cannabis campaigner.” That doesn’t automatically invalidate the paper, but it’s worth noting when the conclusions are being waved around as definitive proof that cannabinoids “don’t work.”
The reality is that the evidence gap is structural and regulatory, not pharmacological. We have decades of observational data, patient reports, and real-world outcomes showing benefit for anxiety, depression, PTSD and insomnia – yet the gold-standard RCT evidence is still catching up because funding, blinding and regulatory hurdles make proper whole-plant studies incredibly difficult.
The Public's Position
Public reaction to the 9 News coverage was swift and overwhelmingly sceptical of the “benefits in doubt” headline. Across hundreds of comments, everyday Australians shared powerful personal testimonies of significant improvements in chronic pain, endometriosis, anxiety, epilepsy, sleep disorders, autism-related symptoms, and overall quality of life after being prescribed medicinal cannabis. Many pointed out the hypocrisy of scrutinising cannabis so heavily while alcohol, opioids, and sleeping pills — which carry well-documented risks and side effects such as morning brain fog — face far less media interrogation. A common sentiment was that the study failed to reflect real-world patient outcomes, with several commenters noting “they clearly didn’t ask the people who actually use it.” The overwhelming message from the public was clear: for a growing number of Australians, medicinal cannabis is not just working — it has become a life-changing option where conventional treatments fell short.
In Closing
This is not an ineffective paper. It’s a research-gap paper dressed up as one. Absence of high-quality RCT evidence is not the same as evidence of absence – especially when the studies that do exist test isolated compounds at fixed doses rather than the multi-molecule, multi-target reality of medicinal cannabis as it’s actually prescribed.
Millions of Australians are already using prescribed cannabis successfully for mental health conditions. The solution isn’t to dismiss the plant; it’s to fund the right trials – whole-plant, titrated, real-world designs – and stop using methodological limitations as a political shield.
As Matt so perfectly summed it up: “The efficacy gap is in the study designs, not the plant.”
We deserve better science, not convenient headlines.
Adam has spent a decade working with unregistered medicines, specialising in Cannabinoid Therapeutics, where he has supported the development, implementation and market entry of multiple cannabinoid product portfolios across Australia, New Zealand, Germany and Brazil. Before working in the medical cannabis field, Adam spent nearly ten years building various B2B businesses in education, investment, and medicinal cannabis, progressing through roles in business development, strategy, product development, and project management. As one of the early experts in Australia's emerging cannabis industry, he has consulted for private and listed cannabis producers and ancillary businesses since 2015. Adam founded and served on the board of The Medical Cannabis Council, Australia's first not-for-profit industry body. A graduate of the Royal Melbourne Institute of Technology with a Bachelor of Entrepreneurship, he is a frequent public speaker and publishes a widely read industry newsletter. His expertise has been featured in major news outlets, including the Sydney Morning Herald, The Australian Financial Review, Nine News, Startup Smart, SBS, SkyNews, MJBizDaily and other prominent publications.
Disclaimer: This information is shared with a global readership for educational purposes only and does not constitute medical or business advice. All patient-related information has been de-identified OR fictional to protect privacy. Nothing in this article is intended to promote the use or supply of medical cannabis to members of the public.
