Age-related trends in cannabis use in Australia. Findings from a series of large nationally representative surveys

Abstract

Aim: We examine age-related trends in past-year cannabis use in a series of nationally representative surveys in Australia.

Methods: We analysed data from the largest nationally representative survey in Australia collected between 2001 and 2019 (National Drug Strategy Household Survey [NDSHS]; N = 157,151). Prevalence of past-year daily/occasional (non-daily)/non-use of cannabis use were estimated using weighted multinomial logistic regression and predicted marginal probabilities. Difference-in-difference analysis was used to examine if trends of cannabis use across age groups were different.

Results: The youngest age group (14-17 s) witnessed the largest increase in past-year abstinence rate from 79% to 92% from 2001 to 2019 (p < .003); the increase in abstinent rate among the 18-24 and 25-39 were relatively moderate (from 68 to 76% and from 81% to 84% respectively; p < .003). The abstinent rate among the 40-54 s and 55-74 s decreased significantly from 93% to 90% and from 99% to 95% respectively (p < .003). There were similar diverging trends in occasional and daily cannabis use, with decreases in both patterns of use observed among the younger age group (14-17 s and 18-25 s) but increases among the older age group (40-54 s and 55-74 s).

Conclusion: There is a diverging trend in cannabis use among younger and older age groups in Australia between 2001 and 2019. Cannabis use substantially decreased among the youngest age group (14-17 s) but modestly increased among older people (55-74 s).