A decade of cannabis-related hospital admissions in Victoria, Australia: A retrospective observational study.

Abstract

Background and aims: Over the past decade, there has been increased lifetime use of illicit and medical cannabis, underscoring the need to examine public health impacts. This includes reports of increased cannabis-related psychosis. In this context, this study aimed to determine all cannabis-related hospital admissions in Victoria, Australia, over a 10-year period to characterise poisonings and mental health harms.

Design: This is a retrospective observational study of the Victorian Admitted Episodes Dataset (VAED) records, which include all hospital admissions in the state of Victoria and are supplied by the Victorian Department of Health.

Setting: Victoria, Australia.

Cases: Hospital records for poisoning (diagnosis code T40.7) and mental health and behavioural disorders (diagnosis codes F12.0-F12.9) related to use of cannabis for the period July 2013 to June 2023 were selected for this study.

Measurements: Crude and age-standardised rates per 100 000 population are reported. Net percentage change over the 10-year study window was estimated using generalised linear models with a log-population offset, contrasting the final year (2022/2023) against the baseline (2013/2014).

Results: There were 39 565 cannabis-related admissions in the 10-year period, including 7263 admissions where cannabis-related harm was the principal diagnosis. The age-standardised rate per 100 000 population was 63.6 for all cannabis-related harm admissions and 11.7 for principal diagnosis cases. The peak annual rate for all cannabis-related harm was observed in 2020/2021 (77.3 per 100 000). There was a 49.0% (P < 0.0001) increase in the rate of hospital admissions with a cannabis-related principal diagnosis, when comparing 2022/2023 with baseline (2013/2014). Overall, harmful use (diagnosis code F12.1) was the most common cannabis-related mental and behavioural disorder. Psychotic disorder (F12.5) was the most common principal diagnosis only (40.1%; n = 2909/7263). When considering principal diagnosis only, the rates were highest in males aged 15-24 years (36.9/100 000), followed by females in the same age group (20.5/100 000). While most principal diagnosis cases involved males, a greater percentage change between the first and last years of the study period was observed for females (+75.1%, P < 0.0001) compared with males (+34.6%, P = 0.003).

Summary: Hospital admissions with a cannabis-related principal diagnosis were 49% higher in Victoria, Australia, in 2022/2023 than in 2013/2014, with the highest rates among people aged 15-24 years and a larger relative increase among females than males; however, trends were non-linear, with admission rates peaking in 2020/2021.