Cannabis policy shifts linked to burns in higher-risk groups

Recreational cannabis legalisation (RCL) in Canada was implemented in October 2018 following a federal announcement in August 2015, with commercialisation occurring in a staggered, province-dependent manner. Cannabis may increase burn risk through hydrocarbon burns from butane hash oil extraction, inhalation injuries, psychomotor impairment, increasing the risk of flame-related accidents and illicit production practices. How burn-related injuries have changed over time around these policy shifts at a population level remains unclear. We conducted an interrupted time series analysis of monthly burn-related hospitalisation rates (2006-2024) across Canada (all provinces and territories except Quebec) and burn-related emergency department (ED) visit rates (2010-2024) in Ontario and Alberta using population-based administrative data. Burns were identified using the Canadian adaptation of the International Classification of Diseases, 10th Revision (ICD-10-CA) codes X00-X19. Intervention periods reflected the RCL announcement (August 2015), enactment (October 2018), commercialisation (private retail expansion; province-dependent) and COVID-19 lockdowns as an effect modifier. Analyses were stratified by age, sex and urban/rural status and by commercialisation strategy groups. Generalised least squares segmented regression was used to estimate level and trend changes across periods. There were 33 346 hospitalisations and 314 962 ED visits for burn-related injuries. No national change in burn injury rates was observed post-RCL when all subgroups were combined. Statistically significant increases in hospitalisation rates were observed among children aged 0-3 in Ontario immediately by 100.7% post-RCL (level β=1.4156; 95% CI 0.4666 to 2.3647; p=0.0039) and among urban residents in early-commercialising provinces over time by 0.6% per month following the RCL announcement period, corresponding to a 12.1% increase over the period (trend β=0.003; 95% CI 0.0005 to 0.0056; p=0.0201). National hospitalisation rates among males increased immediately by 20.6% post-COVID-19 lockdowns compared with the pre-RCL announcement period (level β=0.1561; 95% CI 0.0470 to 0.2652; p=0.0055). ED visits showed few statistically significant changes across periods. RCL-related policy milestones (including the announcement and implementation periods) coincided with increases in burn-related hospitalisations among young children, males and urban residents. More consistent changes in hospitalisations than ED visits suggest shifts concentrated in more severe cases, highlighting the importance of targeted public health strategies and ongoing surveillance during evolving cannabis policy environments.