Key facts
- Doctors are prescribing medicinal cannabis products with THC concentrations up to four times higher than those used in clinical trials.
- There is no upper limit for THC concentration in medicinal cannabis products in Australia.
- Higher-dose products, known as category 5, range from 13% to 88% THC.
- Only two medicinal cannabis products have undergone pre-market evaluation by the TGA.
- Adverse event reports to the TGA show half were related to category 5 products, including psychosis and suicidal behavior.
Doctors in Australia are frequently prescribing medicinal cannabis products with significantly higher concentrations of THC than have been tested for efficacy and safety in clinical trials, a Monash University review has found. These high-dose products, some containing up to 88% THC, are being used for conditions like chronic pain and anxiety, despite limited evidence supporting their effectiveness, particularly at these concentrations.
Researchers highlighted a substantial mismatch between the products being prescribed and the evidence base, with most randomized controlled trials assessing products containing no more than 22% THC. Professor Suzanne Nielsen, a co-author of the review, suggested that the Therapeutic Goods Administration (TGA) consider setting THC concentration limits, potentially at or below naturally occurring levels of around 35%, or aligning with trial levels of 22%. She also called for improved health warnings, labeling, screening, and monitoring of harms.
Data from the TGA indicates that category 5 products, which are high-THC dried herb and concentrated extracts, constitute half of all medicinal cannabis approvals, primarily for chronic pain and anxiety. However, research suggests medicinal cannabis may be no more effective than placebo for anxiety, and evidence for pain reduction is of low quality. Dr. Jack Wilson from the University of Sydney expressed concern that high-THC products, especially smoked or vaporized dried flower, could delay or replace evidence-based treatments and are associated with greater risks of short- and long-term harms.
An analysis of TGA adverse event reports found that half of the cases between mid-2022 and mid-2025 were related to category 5 products, including acute harms like psychosis, cannabis hyperemesis syndrome, and suicidal behavior. A separate review by the Australian Health Practitioner Regulation Agency (Ahpra) raised concerns that profits might be prioritized over patient safety, noting some practitioners issued over 10,000 high-strength THC prescriptions in six months, with consultations lasting mere seconds. The rise of telehealth clinics and direct-to-consumer marketing is also cited as a factor in this profit-driven approach.