A recent study has shed light on trends in medicinal cannabis prescribing in Australia, particularly concerning products with higher concentrations of tetrahydrocannabinol (THC). The research, which examined adverse events reported to the Therapeutic Goods Administration (TGA), suggests a link between higher-strength medicinal cannabis products and an increased incidence of psychiatric adverse events.
Understanding the Shift in Medicinal Cannabis Prescribing
Over recent years, there has been a notable shift towards prescribing medicinal cannabis products containing elevated levels of THC, the cannabinoid known for its psychoactive properties. This trend prompted researchers to investigate potential associated harms. According to a report published in The Conversation, the study found that more than half of all adverse event cases involving unapproved medicinal cannabis products reported to the TGA were related to products with higher THC strengths.
The analysis, which accessed over 1,100 separate adverse events across more than 600 cases reported from mid-2022 to May 2025 via Freedom of Information requests to the TGA, identified psychiatric disorders as the most commonly reported adverse events within this group. These included anxiety, psychotic disorder, and paranoia. The study also noted 14 cases involving suicidal thoughts, behaviour, and attempts.
It is important to note that while a reported adverse event does not definitively establish causation, psychiatric disorders are recognised as potential adverse effects of THC. Researchers expressed concern about the rising frequency of these events, particularly given that such incidents are often under-reported, suggesting actual rates could be higher.
Adverse Events Across Different Product Types
The study also provided insights into adverse events associated with other types of medicinal cannabis products:
- Higher THC Products: Products with THC concentrations ranging from 13% to over 88% were implicated in 54% of all adverse event reports. For context, cannabis plants naturally contain up to 30-35% THC.
- CBD Products: Adverse events were also reported for products containing cannabidiol (CBD), primarily involving gastrointestinal issues such as nausea, vomiting, and stomach discomfort, particularly with oral oil formulations.
- Inhaled Products: The research observed an increase in respiratory adverse events, including cough and shortness of breath, coinciding with a rise in approvals for inhaled medicinal cannabis products. This marks a shift from earlier research where most adverse events involved oral liquids and nervous system disorders were more prevalent.
Overall, products typically inhaled or smoked, such as dried flower, were most commonly associated with adverse events across all categories and for higher THC strength products.
Implications for Prescribing and Patient Safety
The volume of serious psychiatric adverse events, even with likely under-reporting, suggests a need for closer examination of prescribing and monitoring practices for medicinal cannabis. As Cannabiz AU highlighted, this analysis offers “useful early warnings” despite inherent limitations in voluntary reporting systems.
The TGA provides guidance for prescribers to help safeguard patients. For instance, medicinal cannabis products containing THC are generally best avoided for individuals with a current mood or anxiety disorder, or those with a personal or family history of serious mental health conditions like psychosis or schizophrenia. Furthermore, smoking medicinal cannabis is not recommended due to known health risks. Instead, TGA-approved medical devices for vaporising medicinal cannabis are available, which operate at lower temperatures and produce fewer toxins compared to smoking.
Guidance for Patients
Patients using medicinal cannabis are encouraged to discuss potential benefits and risks with their regular GP, who possesses a comprehensive understanding of their health history and other medications. All medicines, including medicinal cannabis, carry the potential for adverse effects, which can range from mild to severe.
If you experience any medicine-related adverse event, it is important to speak with your trusted GP or pharmacist. For severe effects or if you feel significantly unwell, seeking immediate medical attention by calling an ambulance or going to a hospital is advised.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Hemp Gazette does not provide medical recommendations, diagnoses, or treatment plans. Always consult a qualified healthcare practitioner before making any decisions regarding your health or any medical condition. Statements concerning the therapeutic uses of hemp, cannabis, or cannabinoid-derived products have not been evaluated by Australia’s Therapeutic Goods Administration (TGA). Medicinal cannabis products in Australia are accessed via prescription pathways under TGA regulation.
