Abstract Introduction: There has been a recent significant increase in medical cannabis prescribing in Australia despite weak evidence for its effectiveness in treating the most common indications. Concern has been raised about the potential harms of inappropriate prescription of cannabis; however, there have been no prior published cases of psychosis secondary to medicinal cannabis in Australia. Case Presentation: We present a case of a 21-year-old Indigenous male with psychosis following switching from illicitly obtained cannabis to prescription cannabis, which resulted in Othello delusions towards his partner, violence towards her and ultimately an attempt to end his life. Discussion: Cannabis use is linked to the development of a...