New Findings Link THC to Psychiatric Disorders
New research from Monash University has raised alarm over the safety of higher-THC medicinal cannabis products in Australia. The study found that more than half of the adverse events reported to the Therapeutic Goods Administration (TGA) involved these products, with psychiatric disorders being the most common reaction.
Australia has witnessed a shift in medicinal cannabis prescriptions towards products with higher THC concentrations. Currently, over 1,000 unregistered medicinal cannabis products are available for prescription, none of which have been assessed by the TGA for efficacy, safety, or quality.
The study, published in the Australian and New Zealand Journal of Psychiatry, reviewed 1,124 adverse events from 614 reports submitted to the TGA between mid-2022 and May 2025. Researchers found that products categorized as Category 5, containing THC concentrations from 13 per cent to over 88 per cent, accounted for 54.1 per cent of all adverse event reports.
Psychiatric Disorders Predominate
Psychiatric disorders emerged as the leading category of adverse reactions, making up 30.6 per cent of overall reports and 31.9 per cent for higher-THC products specifically. Anxiety, psychotic disorder, and paranoia were the most frequently reported issues, with 14 cases involving suicidal ideation or attempts.
Dried flower was the most common product form involved in adverse events, followed by oral liquids and e-cigarette products. These findings reflect a significant shift from an earlier analysis of TGA adverse event reports up to early 2023, when nervous system disorders were the leading category of adverse events.
Lead author Myfanwy Graham, an NHMRC Postgraduate Scholar and Monash Research Excellence Scholar, emphasised the necessity for improved screening and monitoring of patients using higher-THC medicinal cannabis. “These findings suggest that vulnerable people are not being effectively screened and managed in clinical practice,” she stated.
Graham also pointed out that the actual number of adverse reactions is likely much higher due to the limitations of voluntary adverse event reporting systems. “The fact that we are seeing this volume of psychiatric adverse reactions even with significant under-reporting should prompt a closer look at how these products are being prescribed and monitored,” she added.
Respiratory disorders were the fourth most commonly reported adverse event category. Researchers urge the implementation of more stringent regulations and assessments of medicinal cannabis products to ensure patient safety. This increased scrutiny is crucial for preventing further adverse events.
Last updated: 4 May 2026, 10:19 am
