When medicinal cannabis causes harm in vulnerable patients

Medicinal cannabis prescribing in Australia has increased markedly, including for psychiatric indications where evidence of benefit is limited and of low certainty. The rise of highly commercialised prescribing models has raised concerns regarding patient safety, particularly for those with pre-existing psychiatric or addiction vulnerabilities. This case series describes three young men (aged 20-24) with psychiatric disorders and substance use vulnerabilities who were prescribed medicinal cannabis. The cases illustrate potential iatrogenic harms, including cannabinoid hyperemesis syndrome, cannabis use disorder, paranoia, affective instability and the delaying of other treatment. In two cases, prescribing continued despite emerging adverse outcomes or a formal request for cessation of prescribing from an addiction specialist. These cases highlight the potential iatrogenic harms associated with the current medicinal cannabis prescribing practices in Australia, especially among those with psychiatric and substance use vulnerabilities. More rigorous, evidence-aligned prescribing, clearer exclusion criteria and a lower threshold for discontinuation when harms emerge are needed.