Trends in cannabis use intention around the period of cannabis legalisation in Australia: An age-period-cohort model

Introduction: This study examines age, time period and birth cohort trends in cannabis use intention and weekly use in Australia over a period in which medicinal cannabis was legalised.

Methods: Hierarchical age-period-cohort models were used to analyse the National Drug Strategy Household Survey between 2001 and 2019, including 158,395 participants aged 18-79 years.

Results: The hierarchical age-period-cohort model demonstrated a decrease in likelihood of intending to try cannabis as age increases. Similar age effects were found in intending to use cannabis as often or less often. There was broad-based shift in attitudes for people wanting to try cannabis (2007: b = -0.51 [-0.82, -0.21]; 2019: b = 0.68 [0.38, 0.98]) or use cannabis more often (2007: b = -0.15 [-0.50, 0.20]; 2019: b = 0.83 [0.49, 1.18]). The population trend of weekly cannabis use decreased in the earlier periods but increased since 2013 (b = -0.13 [-0.25, -0.02] vs 2019: b = 0.06 [-0.09, 0.20]). This suggests that legalisation would increase uptake of cannabis and consumption among current consumers. There were distinctive inter-generation variations: people born between 1950s and 1960s had more liberal views towards cannabis use than people born before or after (p < 0.05). There were indications that young people born in the 1990 s are catching up with the baby boomers in using cannabis more often if it was legal.

Discussion and conclusions: There has been a population-based shift in Australia in favourable attitudes towards cannabis use, more so among those born in the 1950s to 1960s than other generations. Liberal attitudes and more frequent cannabis use may put certain cohorts at higher risks of cannabis dependence and related harms.