Non-medical cannabis recently became legal for adults in Canada. Legalization provides opportunity to investigate the public health effects of national cannabis legalization on presentations to emergency departments (EDs). Our study aimed to explore association between cannabis-related ED presentations, poison control and telemedicine calls, and cannabis legalization.

Data were collected from the National Ambulatory Care Reporting System from October 1, 2013, to July 31, 2019, for 14 urban Alberta EDs, from Alberta poison control, and from HealthLink, a public telehealth service covering all of Alberta. Visitation data were obtained to compare pre- and post-legalization periods. An interrupted time-series analysis accounting for existing trends was completed, in addition to the incidence rate ratio (IRR) and relative risk calculation (to evaluate changes in co-diagnoses).

Although only 3 of every 1,000 ED visits within the time period were attributed to cannabis, the number of cannabis-related ED presentations increased post-legalization by 3.1 (range -11.5 to 12.6) visits per ED per month (IRR 1.45, 95% confidence interval [CI]; 1.39, 1.51; absolute level change: 43.5 visits per month, 95% CI; 26.5, 60.4). Cannabis-related calls to poison control also increased (IRR 1.87, 95% CI; 1.55, 2.37; absolute level change: 4.0 calls per month, 95% CI; 0.1, 7.9). Lastly, we observed increases in cannabis-related hyperemesis, unintentional ingestion, and individuals leaving the ED pre-treatment. We also observed a decrease in co-ingestant use.

Overall, Canadian cannabis legalization was associated with small increases in urban Alberta cannabis-related ED visits and calls to a poison control centre.