This study triangulated three data sources to better understand and capture the burden of pediatric cannabis poisonings across Canada. The age-specific rates of cannabis-related poisoning ED visits and hospitalizations of children between the ages of 0 to 11 increased significantly from 2015 to 2021. The largest increases in ED visits for the province of Ontario and hospitalizations for Canada (with the exception of Quebec) occurred from 2019 to 2020. Pediatric cannabis-related poisoning ED visits also increased significantly in Alberta from 2015 to 2021, but the most notable change was from 2017 to 2018, prior to the legalization of cannabis edibles. The largest observed increase in cannabis edible-related events, occurred between 2019 and 2020, coinciding with the largest increases in cannabis-related poisoning ED visits in Ontario, and in pediatric hospitalizations in Canada (with the exception of Quebec). Similarities in the patterns of the ED visits and sentinel surveillance system results suggest that some of the pediatric cannabis poisoning cases presenting to EDs and hospitals may be associated with the ingestion of edible cannabis products as opposed to other forms of cannabis. Overall, the pediatric cannabis poisoning ED and hospitalization rates were higher after legalization of cannabis (October 2018) and cannabis edibles (October 2019) compared to pre-legalization. This was consistent across all outcomes in this study. These findings provide additional support to existing evidence from the US [6–10] and from four provinces [11, 12, 14] in Canada.

It is important to note that poisonings with a milder clinical presentation (where the child presents with few or no obvious symptoms) may not be captured in hospitalization or ED visit data, as the child/caregiver may not seek formal care. However, poison centre data may reveal a greater burden of pediatric cannabis/edible poisonings as caregivers may reach out to poison centres for general information on managing symptoms at home and ask for guidance on whether they should seek formal care. In fact, data from the British Columbia Drug and Poison Information Centre show that the proportion of cannabis-related calls from 2013 to 2018 increased the most for those involving children between the ages of 0–12 compared to other age groups and that most of those calls were because the child had ingested cannabis edibles [17]. This highlights the importance of examining multiple data sources to get the most complete picture of cannabis-related poisonings in Canada. Future studies should consider reporting on poison centre calls, the type of cannabis involved and their origin to further assess the role that different cannabis products play in poisonings. Given that specific regulations on distribution and sale of cannabis can vary across Canadian jurisdictions, it could be important to explore this at the provincial and territorial levels.

The qualitative analysis from the sentinel surveillance data enriched our understanding of the findings by providing context surrounding edible-related cases among children. Close to nine in ten (87.7%) pediatric edible-related cases were due to lack of safe storage practices/easy access. This evidence supports previous recommendations that were made on the issue, particularly for regulations around safe storage and child-resistant packaging [7, 10, 12, 13, 17–19]. In addition, some of the pediatric cannabis edible-related poisonings (7.2%) occurred because a family member or caregiver was unaware that some of the sweets were edibles and accidentally gave them to children. These findings underscore the need to continue targeted public health interventions among adults related to (1) safe storage of cannabis products in households and (2) communication with family, friends, and caregivers related to cannabis edibles in the household to mitigate unintentional pediatric ingestion.

Another way to reduce cannabis-related harms among children would be to raise awareness on the risks associated with consuming illegal cannabis. Under the Cannabis Regulations, regulations pertaining to edibles, including restrictions on packaging (namely childproof and restrictions to mitigate appealing to youth) and quantity (capped at a maximum of 10 mg of THC per package), were created to reduce harms associated with consuming edible cannabis [2]. Illegal cannabis edible products are often not in childproof packaging and have colourful/appealing packaging, including look-alike packaging similar to recognizable confectionary products, and very high levels of THC, which can cause serious harm to children [2]. Some individuals may not be cognizant of the increased risk associated with illegal and unregulated cannabis products. The Government of Canada has published information on how to recognize legal and illegal cannabis, and why legal cannabis should be chosen [20]. Targeted public health messaging highlighting this resource could be beneficial. One systematic review [18] and one Canadian study [11] underlined the importance of determining whether legal or illegal products were more common among edible-related exposures among children. Unfortunately, most of the available Canadian data capturing cannabis-related harms are found in administrative data sets, which do not contain information on source of cannabis. Future studies are warranted to address this gap in evidence.

This is the first study reporting on trends in almost nationally representative rates of pediatric cannabis-related poisoning hospitalizations. This study addressed a gap in evidence flagged in two previous Canadian studies [11, 12] by providing novel data on trends for poisonings related to cannabis edibles captured through sentinel surveillance. Another key strength is the mixed-methods design of this study and the triangulation of three data sources, which provided additional context to the findings and helped better characterize public health and safety impacts of cannabis in Canada.

There are some limitations to note. First, the geographic coverage is incomplete. Cannabis-related poisoning hospitalization rates do not include Quebec, and age-specific rates of ED visits could only be derived for Ontario and Alberta. The CHIRPP collects data from select Canadian hospitals, and findings from the analysis may not represent all cannabis edible-related events in Canada. Second, the CHIRPP database is continuously updated and as a result, some years may not yet have complete data; however it is expected that the period covered in this manuscript will have a high completion rate as it does not include data from 2022. Third, there is some overlap between the datasets presented in this manuscript and supporting Canadian studies. We used the NACRS dataset for ED visits in Ontario and Alberta, which is the same dataset that was used in two existing Canadian studies [11, 12]. There is also some overlap with the CHIRPP dataset that was used in this study with a 2020 Canadian article that stated there were 35 edible cases from 2016 to 2019 [13]. Therefore the similarity in patterns of our results with those studies is not suggestive of a stronger trend. Fourth, Indigenous peoples including Inuit, Metis, and First Nations, and people who live in rural areas may be under-represented in the CHIRPP database. Fifth, lack of data on the source and type of cannabis ingested limits the analyses of cannabis poisoning ED visits and hospitalizations (not specific to edibles). While similarity in patterns of cannabis edible-related events from CHIRPP does seem to suggest that edible cannabis products may be contributing to the increasing rates in cannabis-related poisoning ED visits and hospitalizations, no definitive conclusion can be made. It should also be noted that significant events over time such as the 1) implementation of the Cannabis Act [1] in 2018, 2) amendment to the Cannabis Regulations [2] in 2019, and 3) the COVID-19 pandemic beginning in March 2020 may have influenced observed patterns and trends. As limited time has elapsed since cannabis legalization and regulation, caution is recommended when interpreting pre- and post-legalization trends based on data presented in this report. Sixth, health-seeking for substance-related harms may have changed due to public health measures implemented during the COVID-19 pandemic and may have led to an under-representation from March 2020 to June 2021. Analyses by CIHI show about 9,300 fewer ED visits per day across Canada compared to the pre-pandemic period (January to December 2019), with the greatest reduction among children and youth (0–19 years) [21]. The decrease in the rate of cannabis edible-related cases in 2021 compared to that in 2020 from CHIRPP records could also be attributed to the analysis by CIHI. Seventh, the rates presented in these analyses represent the most severe cannabis/edible-related poisoning cases, which is likely an under-representation of the true burden of pediatric cannabis poisonings in Canada. Lastly, it is possible that since cannabis has been legalized, parents and caregivers may feel more at ease disclosing the source of the poisoning (cannabis) and seek formal care for their child [11].