Introduction: Australians are leading consumers of cannabis and have some of the highest rates of cannabis use disorder (CUD) globally. As cannabis policies become more liberal worldwide, it is important to monitor changes in rates of cannabis use and those most at risk of harm. We used data from the largest national mental health survey in Australia to examine changes in the prevalence, correlates, and comorbidity of past 12-month cannabis use and CUD from 2007 to 2020-22.

Methods: Data were drawn from the 2007 (n = 8,841) and 2020-22 (n = 15,893) Australian National Surveys of Mental Health and Wellbeing (NSMHWB; age range: 16-85). The prevalence of cannabis use and CUD were estimated and analyses examined individual correlates. Logistic regression with year of survey as an interaction with these correlates investigated changes over time.

Results: In 2007 and 2020-22, recent cannabis use among the Australian adult population 16+ was stable at 6.7%, while CUD decreased from 1.0% (95%CI: 0.7%-1.3%) to 0.6% (95%CI: 0.4%-0.8%). Respondents were significantly more likely to report CUD if they were younger (16-25 years old), male, had initiated cannabis use <18-years of age, reported recent polysubstance use, exhibited other substance use and mental health disorders, and had visited a range of mental health services (odds ratios (ORs) 3.26-78.00). Compared to 2007, the association between younger age and CUD was stronger in 2020-22 (OR 2.39, 95%CI: 1.20–4.77), whereas the association between polysubstance use and CUD was weaker (OR 0.42, 95%CI: 0.20–0.91).

Conclusions: Findings suggest that population-level CUD may have decreased over time but CUDs have become more common among young people. As cannabis products become more accessible, it is crucial that we monitor trends in use and develop a public health response to assist those most at risk of harm.