High-THC medicinal cannabis linked to psychiatric harms: new AU data

What the study found

A rapid review published this month in Drug and Alcohol Review, led by researchers at Monash University, examined 1,124 adverse events drawn from 614 reports submitted to the TGA involving medicinal cannabis products between mid-2022 and May 2025.

The headline finding: Category 5 products — those containing THC concentrations ranging from 13 to more than 88 per cent — accounted for 54.1 per cent of all adverse event reports. Psychiatric disorders were the leading category of adverse events overall (30.6 per cent of all reports) and specifically within the higher-THC group (31.9 per cent). The most frequently reported psychiatric adverse events were anxiety, psychotic disorder, and paranoia. Fourteen cases involved suicidal ideation, suicidal behaviour, or a suicide attempt.

This is not the first signal. The TGA launched a public consultation in August 2025 specifically because of accumulating concern about the safety risks associated with unapproved, higher-THC medicinal cannabis products. What the Monash analysis adds is a structured pharmacovigilance lens — applying systematic examination to the adverse event data in a way the reporting database alone does not surface.

There is a structural reality underneath this data worth naming: more than 1,000 unregistered medicinal cannabis products are currently available for prescription in Australia through the Special Access Scheme and the Authorised Prescriber pathway. None of these products has been assessed by the TGA for efficacy, safety, or quality before reaching prescribers and patients. The regulatory framework that enabled rapid access is the same one that has left a significant pharmacovigilance blind spot.

The both-and

If you have been prescribed medicinal cannabis and found real relief — for pain, sleep, anxiety — this research will land differently than it might for someone weighing up whether to try it for the first time. Both positions are valid, and the evidence speaks to both.

For the sceptical reader: the psychiatric adverse event signal in higher-THC products is not trivial. The RACGP, in its February 2026 submission to the TGA, called the current regulatory situation a major public health risk and backed tighter controls alongside a crackdown on what it described as unethical telehealth prescribing. The prescribing growth in Category 5 products has outpaced the evidence base — not because patients have been deceived, but because the access architecture made it structurally easy to prescribe high-THC products without the quality and efficacy gating that registered medicines ordinarily require.

For the person already using medicinal cannabis: the signal here is product-specific, not a global condemnation of all cannabis-derived therapies. Lower-THC and CBD-dominant formulations have a different evidence and safety profile. The Conversation’s explainer on this research — written by the researchers — is worth reading for the nuance. The study does not argue that all medicinal cannabis is unsafe. It argues that the highest-concentration THC products have a psychiatric safety signal that is now too large to ignore in clinical practice.

Two things can be simultaneously true: medicinal cannabis helps some people in ways other medicines have not, and the unregulated proliferation of very high-THC products through low-scrutiny prescribing pathways has created a pharmacovigilance problem the system is now catching up to.

2 cents

If you are currently taking a medicinal cannabis product, look at the label or ask your prescriber: what category is this? If the answer is Category 5 — THC above 13 per cent — the grounds for a specific conversation are in the paper linked above. Track your mood. Note any anxiety, paranoia, or unusual thought patterns. Report new psychiatric symptoms to your prescribing doctor promptly, not at your next routine review.

The market for medicinal cannabis in Australia has grown faster than the clinical evidence base. The TGA is consulting. The RACGP is calling for structural reform. The gap between prescription growth and evidence quality is narrowing, but it is not yet closed.

Your prescriber’s job is to match the product to your specific clinical picture — including psychiatric history — not simply to facilitate access. That conversation, with the specific product category named, is worth having now rather than later.

Verdict

Verdict: maybe — the signal is real; the individual picture matters.

The psychiatric adverse event data for high-THC medicinal cannabis products is clinically significant and grounds a specific conversation between anyone using Category 5 products and their prescribing doctor. Lower-THC and CBD-dominant formulations carry a different evidence profile. Watch the TGA’s consultation outcome and any subsequent regulatory changes as they emerge.

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Sources cited

1. Graham et al 2026 — Higher THC Concentration Medicinal Cannabis Products: Efficacy and Safety Considerations — Drug and Alcohol Review
2. The Conversation — Higher-strength medicinal cannabis may be linked to a disturbing pattern of side effects, our study shows
3. RACGP newsGP — ‘Major public health risk’: RACGP backs medicinal cannabis reform
4. TGA — Planned consultation to address growing safety concerns of unapproved medicinal cannabis products in Australia