Cannabis consumption in Australia 2018-2025: Socio-economic and regional trends from wastewater and survey data

This study examined whether socio-economic status (SES) and geographic remoteness are associated with cannabis consumption across Australia by comparing wastewater-based surveillance (WBS) data and self-reported cannabis use in national household surveys.

We compared cannabis consumption estimates from 6 years of wastewater data from the National Wastewater Drug Monitoring Program (NWDMP) with cannabis use data from the National Drug Strategy Household Survey (NDSHS). We categorised the Index of Relative Socio-economic Advantage and Disadvantage (IRSAD) into quartiles for each wastewater catchment area. Three remoteness categories (Major Cities, Inner Regional, Outer Regional/Remote) from the Australian Bureau of Statistics were used to categorise wastewater and survey data by degree of urbanisation. Trends were analysed using linear regression, analysis of variance and logistic regression.

Wastewater: Estimated cannabis consumption in wastewater increased between 2018 and 2025 annually across SES quartiles from 2.9% [95% confidence interval (CI) = 2.0-3.9%] for the most disadvantaged to 5.2% (95% CI = 3.2-7.3%) for the second most disadvantaged quartile. The annual rates increased for all three categories of remoteness and ranged from 3.6% (95% CI = 2.2-5.2%) to 4.8% (95% CI = 4.2-5.5%) for Inner Regional and Major Cities, respectively. Consumption was statistically significantly higher in the most disadvantaged SES quartile (3000 mg/1000 people/day, 95% CI = 2900-3100) than in the least disadvantaged (1200 mg/1000 people/day, 95% CI = 1100-1200, P < 0.001). It was also highest in the most remote category (2400 mg/1000 people/day, 95% CI = 2300-2500), compared with the most urban category (980 mg/1000 people/day, 95% CI = 960-1000, P < 0.001).

In the NDSHS the prevalence of regular cannabis use was higher in the most disadvantaged SES quintile (6.1%, 95% CI = 5.2-7.3% in 2022/2023) than in the least disadvantaged (4.2%, 95% CI = 3.5-5.1% in 2022/2023). It was also higher in the most remote category (5.9%, 95% CI = 4.8-7.4%) than in the most urban category (4.3%, 95% CI = 3.9-4.8%), in all survey years (i.e. 2016 and 2019).

Wastewater-based surveillance and survey data describe similar trends in population cannabis use by socio-economic status and urban remoteness in Australia from 2018 to 2025.