High-THC Medicinal Cannabis Prescribing in Australia Far Outpaces Clinical Evidence, Review Finds
Key Insights
A Monash University review found that medicinal cannabis products prescribed in Australia contain up to 88% THC, yet randomized controlled trials have only tested products up to 22% THC.
Category 5 products account for nearly half of all unapproved medicinal cannabis applications, with adverse events including psychosis (search), suicidal behavior, and cannabis hyperemesis syndrome (search).
AHPRA identified practitioners issuing over 10,000 high-THC prescriptions in six months, with some consultations lasting only seconds, raising concerns that profits are prioritized over patient safety.
Australian patients are routinely being prescribed medicinal cannabis products with THC concentrations up to four times higher than any product tested in randomized controlled trials, according to a rapid review published in the journal Drug and Alcohol Review.
Researchers from the Monash Addiction Research Centre evaluated the available evidence for the efficacy and safety of higher-THC potency medicinal cannabis products, screening 9,969 studies from the past decade. Only 15 studies met the eligibility criteria for inclusion, two of which were conducted in Australia.
"There is a real mismatch between the evidence we have to draw on and the products being prescribed and used," said Professor Suzanne Nielsen, a co-author of the review and researcher at the Monash Addiction Research Centre.
The Evidence Gap
Category 5 products — the Therapeutic Goods Administration (search)'s (TGA) classification for unapproved medicinal cannabis — range from 13% to 88% THC (delta-9-tetrahydrocannabinol) (search), the main psychoactive ingredient in cannabis. Yet the review found that randomized controlled trials, the strongest form of clinical evidence, have only assessed products containing up to 22% THC.
Of more than 1,000 medicinal cannabis products available in Australia, only two have undergone pre-market evaluation by the TGA for quality, safety, and efficacy. There is currently no upper limit for THC concentration allowed in medicinal cannabis products.
Long-term efficacy data were especially sparse. Five of the 15 included studies used only a single dose, limiting any assessment of sustained therapeutic benefit or harm.
Adverse events reported in the studies — predominantly dizziness, cough, nausea, drug highs, and anxiety (search) — were mild to moderate and tied to the total THC dose rather than its concentration.
Prescribing Patterns and Safety Concerns
According to TGA data, chronic pain (search) and anxiety (search) drive the majority of prescriptions, with category 5 products making up half of all approvals. Professor Nielsen noted that prescribed medicinal cannabis had historically been in the form of oral oils, but approvals have "dramatically pivoted toward high-THC smoked or vaporised dried flower."
"This doesn't really match where the evidence is for what works," Nielsen said. "There's very limited evidence in general for medicinal cannabis, but particularly for these high-concentration THC products and inhaled forms."
The safety concerns are underscored by adverse event data. An analysis of 614 medicinal cannabis adverse event reports to the TGA between mid-2022 and mid-2025, published in the Royal Australian and New Zealand College of Psychiatrists' journal, found that half were related to category 5 products. Reported harms included psychosis (search), cannabis hyperemesis syndrome (search), and suicidal behavior. Psychiatric disorders — including anxiety (search), psychosis, and paranoia — were the leading adverse event category, followed by nervous system and respiratory disorders.
A TGA spokesperson confirmed that 27 cases involving medicinal cannabis had been voluntarily reported to its adverse events database so far in 2026, though a report does not constitute proof that the product caused the adverse symptoms.
Regulatory Scrutiny Intensifies
A 2025 review of cannabis prescribing by the Australian Health Practitioner Regulation Agency (search) (AHPRA) found concerns from medical regulators that "profits are being prioritised over patient safety in some medicinal cannabis prescribing practices." The review identified practitioners who had individually issued more than 10,000 prescriptions for high-strength THC medicinal cannabis products in six months, with one practitioner issuing over 17,000. Cases of consultations lasting just a few seconds were also highlighted.
Dr. Jack Wilson of the University of Sydney's Matilda Centre for Research in Mental Health and Substance Use expressed concern that these products might delay or replace evidence-based treatments. "The regular consumption of THC is also associated with a greater risk of short- and long-term harms, possibly making the patient's condition even worse," Wilson said.
He added that research has found medicinal cannabis is no more effective than placebo at reducing anxiety (search) symptoms, and a 2018 review concluded there was low-quality evidence that cannabis may be associated with only small reductions in pain.
Dr. Michael Wright, president of the Royal Australian College of General Practitioners (search), echoed these concerns: "Profits can't be prioritised over patient safety. Online cannabis clinics operating as businesses create conflicts of interest, fragment care and put patients at risk."
Calls for Reform
Professor Nielsen suggested the TGA should consider setting THC concentration limits at or below the levels naturally occurring in the cannabis plant, at about 35%, "or even at 22% in line with what has been tested in trials." She also called for health warnings, better product labeling, and improved screening and monitoring of harms.
Myfanwy Graham, co-author of the study and Monash research excellence scholar, emphasized that "heightened screening and monitoring of patients is essential because we know not all information is being communicated from external telehealth or private clinics to GPs."
AMA Queensland (search) president Associate Professor Erica Gannon said the study reaffirmed what medical bodies have long maintained: "Products are being prescribed for conditions for which there is no evidence of their efficacy or to patients with co-morbidities where medicinal cannabis is contraindicated."
The downstream effect, Gannon noted, is an increase in presentations of THC-induced psychosis (search) and other harmful effects, further straining emergency department staff.
The TGA's own review of the unapproved medicinal cannabis framework, which received 786 submissions before closing in October 2025, found the supply pathway was no longer fit for purpose. The TGA has yet to specify when reforms will come into effect.
Pressure appears to be having some impact: the volume of medicinal cannabis units sold in Australia fell by almost 30% following AHPRA and the TGA's crackdown on problematic prescribing practices, according to data from the Department of Health, Disability and Aging.
Queensland remains a particular hotspot, having issued more medicinal cannabis prescriptions since licensing began in 2016 than all other states combined — 167,000 scripts compared with 156,000 across Victoria, New South Wales, Western Australia, and South Australia combined, according to AMA Queensland (search).