Background: Cannabis-related emergency department visits can be an entry point for youths to mental health and substance use care systems. We aimed to examine trends in cannabis-related emergency department visits as a function of youths’ age and sex.

Methods: Using administrative data, we examined all visits to emergency departments in Ontario, Canada, from 2003 to 2017, by youth aged 10–24 years (grouped as 10–13, 14–18 and 19–24 yr) to determine trends in cannabis-related emergency department visits. Cannabis-related visits were identified using International Statistical Classification of Diseases and Related Health Problems, 10th Revision codes for cannabis poisoning and mental disorders due to cannabinoids. We categorized presentations as “less severe” versus “more severe” using scores assigned by nurses at triage.

Results: We examined 14 697 778 emergency department visits. Cannabis-related visits increased from 3.8 per 10000 youths in 2003 to 17.9 in 2017, a 4.8-fold increase. Rates increased for both sexes and each age group. Males were more likely to have a visit than females (rate ratios ≥ 1.5 in 2003 and 2017). The number of cannabis-related visits in 2017 was 25.0 per 10 000  among youth aged 19–24 years, 21.9 per 10 000 among those aged 14–18 years, and 0.8 per 10 000 among those aged 10–13 years. In 2017, 88.2% of cannabis-related visits and 58.1% of non–cannabis-related visits were triaged as “more severe,”. Similarly, in 2017, 19.0% of cannabis-related visits and 5.8% of non–cannabis-related visits resulted in hospital admission.

Interpretation: Rates of cannabis-related emergency department visit by youths aged 10–24 years increased almost fivefold from 2003 to 2017, with increases in visit severity and hospital admissions. These trends describe an emerging public health problem, and research is needed to identify the causes of this increase and the health and social consequences of cannabis-related visits for these youths.....