Response to Smyth & McCarron: Increases in cannabis‐attributable emergency department visits during different phases of the pre‐ and post‐legalization period are multi‐factorial

We thank Smyth & McCarron [1] for taking the time to comment on our recent publication [2]. We agree that our paper did not fully discuss the process towards non-medical legalization in Canada for an international audience. To clarify: in the pre-legalization period, there was widespread access to an illicit cannabis market, including retail dispensaries and on-line delivery services [3]. In addition, there was access to medical cannabis, which began in 2001 for individuals with a limited list of health conditions, and was expanded in 2014 for individuals who received authorization from a physician that they would therapeutically benefit from medical cannabis [4]. There are several comments made by Smyth & McCarron that we would like to address. First, they question whether the rapid increase in emergency department (ED) visits during the 2.75-year pre-legalization period used in our study is representative of the longer pre-legalization period in Canada. In Fig. 1, we present visit rates over a longer pre-legalization period beginning in January 2010, which shows that ED visits due to cannabis have indeed been rapidly increasing over time for at least 8.5 years prior to legalization. There is a modest monthly slope increase (incident rate ratio = 1.008; 95% confidence interval = 1.005–1.011 for adults aged 15+ years) following the public commitment in December 2015 by the federal government to legalize non-medical cannabis. Sustained increases pre-legalization are consistent with prior work where we found that hospitalizations due to cannabis in Ontario began increasing in 2008 [5]. We speculated that this strong pre-legalization trend was multi-factorial, including increasing access to medical and illicit sources, changing stigma towards cannabis use (e.g. individuals become both more likely to use cannabis and more likely to report use of cannabis) and increasing cannabis potency [e.g. tetrahydrocannabinol (THC) concentration] over time [4-6] (Figure 1). Secondly, to clarify, we observed that the first phase of legalization—with strict controls on retail stores and product types (e.g. no legal vapes, edibles or concentrates) was associated with a statistically significant attenuation of the pre-legalization slope of increasing rates of ED visits due to cannabis over time, not a decrease in visits. While this is indicated throughout our paper, we agree that our concluding paragraph could make this clearer and should have the following italicized words added: ‘We found that the trend in cannabis-attributable ED visits decreased relative to the pre-legalization trend following recreational cannabis legalization with strict retail controls’. Thirdly, Smyth & McCarron suggest that the presence of an illicit or gray cannabis market in Canada and changing social norms in the lead-up to legalization reduces the generalizability of these findings to other countries considering legalization. Importantly, illicit cannabis is available in every region of the world, and we believe that a transition period from an illicit to legal market is part of the legalization process [7]. Cannabis use has also become less stigmatized and more socially acceptable around the world, regardless of legal status [8]. The recent experience of other countries proceeding with non-medical legalization, such as Germany, also suggests that policy shifts towards legalization are likely to have similar lead-in periods as in Canada, with potential changes in cannabis-related stigma and drug enforcement [9]. Importantly, while we believe that the Canadian experience regarding legalization will generalize to other countries, we highlight that legalization itself can take multiple forms. Our ongoing research suggests that regulatory decisions such as allowing or restricting cannabis marketing and promotion, retail access, product types and cannabis potency can all influence cannabis use and related health outcomes post-legalization [10-13]. Consequently, as other countries proceed towards legalization, we caution that policies that allow higher levels of commercial access risk important population-level changes in cannabis use and consequent harms. Daniel Myran: Conceptualization; funding acquisition; methodology; formal analysis; investigation; visualization. Michael Pugliese: Data curation; formal analysis; investigation; methodology; software; visualization. Peter Tanuseputro: Conceptualization; funding acquisition; methodology; supervision. Monica Taljaard: Conceptualization; formal analysis; investigation; methodology; supervision; visualization. This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health (MoH) and the Ministry of Long-Term Care (MLTC). This study was also supported by a project grant (452360) from the Canadian Institute for Health Research (CIHR). The analyses, conclusions, opinions and statements expressed herein are solely those of the authors and do not reflect those of the funding or data sources; no endorsement is intended or should be inferred. None.

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