Cannabis hospitalisations rise 49% in ten years as psychosis cases climb

Doctors have raised concerns about rising rates of cannabis-related psychosis for a long time. A new ten-year study shows those concerns are well founded. Researchers examined almost 40,000 cannabis-related hospital admissions in Victoria between 2013 and 2023. Over that time, cases where cannabis was the main reason someone ended up in hospital increased by 49%.

Psychotic disorder was the leading cause of these hospitalisations. It accounted for 40.1% of cases where cannabis was the primary reason for admission. Poisoning made up less than 12% of cases during the same period. This suggests mental health issues related to cannabis are more common than physical poisoning.

These were not quick visits for most patients. Sixty-eight percent stayed in hospital for longer than 24 hours. The average stay lasted a week for all cases involving cannabis. More than 1,500 people required admission to an intensive care unit or ICU during this time.

Males aged 15–24 still represent the largest total group hospitalised overall. However, the study showed the largest increase over the decade was in younger women and adults aged 65 and older. Public health initiatives do not necessarily focus on these specific groups.

Admissions peaked during the COVID pandemic in 2020 and 2021. Isolation, job losses and broader mental health struggles may have contributed to many people using more cannabis. Wastewater monitoring confirmed a rise in cannabis use around this time.

Unlike some illicit supply chains disrupted by border closures, local cannabis supply remained largely accessible. Changing social perceptions may also play a role as cannabis becomes more acceptable. People may simply feel more comfortable telling doctors about their cannabis use.

Higher-strength cannabis is likely to play a role in the increase. Severe psychiatric and respiratory reactions occur with products containing higher levels of tetrahydrocannabinol, or THC. That component causes drowsiness or a high.

It is hard to know if prescribed medicinal cannabis or illicit cannabis explains this increase in hospitalisations. Hospital coding systems rarely distinguish between legal and illicit cannabis use. Many people use both types during the same period.

Fewer Australians take prescribed cannabis compared to illicit cannabis. Legal products still come with risks, especially high-potency ones inhaled for safety reasons. Some frequently prescribed products contain up to 88% THC. High-volume telehealth clinics that do not properly screen people may contribute to the rise in severe mental health adverse events.

This is not just a Victorian issue and some studies suggest other states have higher rates of cannabis use. When legal access expands via profit-driven commercial models, cannabis-related psychosis hospitalisations tend to rise. Safety regulations need to keep pace with changing products and increased availability. Tailoring prevention campaigns for vulnerable groups offers an opportunity to improve outcomes.