In 2018, Canada implemented the legalization and regulation of cannabis use and supply for adults. This fundamental policy reform was guided by and set to advance multiple primary policy objectives, notably improved public health and youth protection, including the prevention of youth cannabis use. ¹ Under Canada's legalization framework (centrally defined by the federal “Cannabis Act”), cannabis may be used and procured from regulated sources by adult-age individuals; the corresponding legal minimum age is 19 years or older in most provinces (with the 2 exceptions of Alberta [18] and Quebec [21]); while there is a general tolerance approach to small amounts of cannabis for use by underage youth (adolescents), they may be charged for possession of >5 g of dried cannabis or equivalents. ¹

Youth are a distinctly vulnerable group for cannabis use-related harm for several reasons: first, because Canada has historically had among the globally highest cannabis use rates among youth; second, because young people, and in particular adolescents, beyond general substance use-related vulnerabilities present markedly increased risks for severe adverse (e.g., cognitive, mental health, and psychosocial) health outcomes especially when intensive (e.g., frequent/high-potency) and/or chronic cannabis use is involved. ² On this basis, selected voices had explicitly advocated against legalization policy in Canada as they expected it to not work in favour of young people's health and welfare. While select recent reviews have focused on Canadian legalization's effects on youth (e.g., ages 15–24, largely including individuals at legal age for cannabis use) and have found mixed effects, we will briefly consider developments for the subgroup of underage youth, that is, adolescents, who are formally excluded from the scope—and possible benefits—of legalization policy while most vulnerable to cannabis use-related health and social problems. ³

Half a decade following legalization's implementation, select while limited empirical data indicators focusing on key cannabis-related outcomes for adolescents are available in different areas. For primary use and related health outcome data, the prevalence of cannabis use (past 12 months) in respondents ages 16–19 increased from 36% in 2018 to 43% in 2023 in the National Canadian Cannabis Survey (CCS). In both the National Canadian Youth Smoking Survey/Canadian Student Tobacco, Alcohol and Drugs Survey (18% in both 2018–2019 and 2021–2022 cycles) and the provincial Ontario Student Drug Use and Health Survey (19% in 2017 and 17% in 2021), the prevalence of cannabis use among total respondents (grades 7–12) remained generally unchanged through legalization; both surveys indicated recent use rates >30% among older adolescents in grades 11 and 12. A pre–post design-based analysis of data comprising Ontario's secondary student population for the period of 2001–2019 showed overall mixed patterns for cannabis use initiation; however, cannabis legalization, compared with the prelegalization period (2001–2017) was found to be associated with increased likelihoods of any cannabis use (odds ratio [OR]: 1.31; 95% Confidence Interval [CI], 1.12 to 1.53), daily cannabis use (1.40; 1.09 to 1.80) and cannabis dependence (1.98; 1.29 to 3.04). ⁴ A health-administrative data-based assessment of cannabis-related hospitalizations in Canada's 4 largest provinces (Alberta, British Columbia, Ontario, and Quebec), found moderate but significant—while relatively smaller compared with older ages—increases including for cannabis-related psychosis, poisoning, withdrawal and harmful use for the subgroup ages 15–24 years to be associated with legalization, specifically during the “commercialization” (2020–2021) compared with the prelegalization (2015–2018) period. ⁵ Among respective underage youth in Alberta (<18) and Ontario (<19) in the period 2015–2019, legalization was associated with a 20.0% (95% CI, 6.2% to 33.9%) increase-equivalent for cannabis-related disorder/poisoning presentations to emergency department settings. ⁶

For cannabis and driving-related behaviours, an over time analysis identified substantive declines in the prevalence of driving within 1 h following cannabis use—from 19.9% [15.0% to 25.8%] in 2001 to 6.8% [5.7% to 8.1%] in 2019; (p < 0.0001)—among Ontario adolescents in possession of a valid driver's license; however, there were no significant changes specifically associated with the implementation of legalization in 2018. ⁷ In its assessment of cannabis sourcing patterns among active (past 12 months) users, the CCS found that among 16–19-year-old respondents, 41% reported “legal purchase” (e.g., from a legal store/website) and 43% “social source” (e.g., family and friends) as their “usual” cannabis source in 2023. National Uniform Crime Reporting data-based time series analysis showed that incidents of total police-recorded cannabis-related offences among adolescents (12–17 years) in Canada significantly decreased (males: 32,000 to 2,508 [estimated step effect change in daily offence incidents: −53.0% (22.7%); p < 0.0001]); females: 8,971 to 558; [−62.1% (34.3); p < 0.0001]) from the pre-legalization (2015–2018) to the post-legalization (2018–2021) period. ⁸ While similar major declines were identified specifically for cannabis possession (i.e., typically use-related) offences (males: 29,015 to 1,603; females: 8,377 to 367) through these periods, this particular subtype of cannabis offense incidents, albeit at relatively low levels—and different from observations for adults—remained as the respective majorities of the enforced cannabis offence total among adolescents through legalization. ⁸

More than 5 years following the implementation of the cannabis legalization policy in Canada, the relatively limited (with some not strictly focusing on the population of interest) data available suggest a mix of developments for key outcome indicators among adolescents. First, present information indicates continuously steady—while at comparably high levels—prevalence of cannabis use from before to after legalization. While related data somewhat vary across provinces, they may also represent an interruption of long-term previously declining trends (e.g., post-2000) in cannabis use in this vulnerable age group. These developments suggest that the legalization policy's (widely emphasized) objective to keep “cannabis out of the hands of youth” has remained unachieved for adolescents as a primary subgroup of concern and interest for policy outcomes. In addition, there is some evidence that cannabis use among adolescents may occur in ways characterized by higher risk for, and/or result in more tangible health-related harm (e.g., including hospitalizations) from before to after legalization. These developments are somewhat contrasted by seemingly steady levels of driving under the influence of cannabis as a key risk factor for possible cannabis-related injury and/or death. The outcome data considered overall, however—similar to related observations made in the United States—do not suggest clear signals of improvements in direct cannabis-related health protection among adolescents as associated with legalization.^1,3

Additional while more encouraging evidence characterizes developments for essential socio-legal outcome indicators among adolescents. First, while virtually no under-legal-age youth report obtaining their cannabis from illegal (e.g., criminal) sources in current legalization realities, about equal portions report cannabis acquisitions mainly from “legal” and “social” sources under conditions of legalization. This, for welcome developments, points to a probable, substantive separation of adolescents from exposure to illegal/criminal drug markets, including possible other illicit substances, in contexts of cannabis sourcing. At the same time, it needs to be acknowledged that present provisions and efforts to keep adolescents from accessing cannabis through “legal” (but for legal-age adults) and/or “social” sources are widely ineffective. These alternative ‘grey' sourcing practices may at least, to some extent, provide underage cannabis consumers with more “regulated” and/or potentially safer cannabis products than those typically accessed from nonlegal sources. Yet, overall, these shifts appear to largely represent displacement effects rather than tangible reductions of cannabis access and availability which may have facilitated corresponding decreases in cannabis exposure in this vulnerable age group.

A second issue concerns ongoing enforcement patterns of cannabis-related offences involving adolescents. The totals of enforced cannabis offences among minor-age youth have substantially declined from pre- to post-legalization, which ought to be interpreted as a sensible and welcome development towards the health and welfare protection of these vulnerable individuals at a pre-adult age. However, a small but non-trivial number of incidents, specifically including cannabis possession offense incidents, remain enforced against adolescents, that is, an offence category typically related to personal use that may involve a criminal arrest/charge for small (i.e., >5 g) cannabis amounts. ⁸ The common, mostly long-term adverse consequences (e.g., judicial penalties, personal stigma, record entries possibly impeding crucial advances in life) arising from such enforcement especially for underage individuals appear questionable and/or excessive—especially in a wider, social environment of universal “cannabis normalization” where not only every legal-age adult may freely obtain and consume cannabis but related promotion messaging actively reaches many underage youth.^1,9 Here, legalization's current provisions appear to feature disconcerting contradictions and may not only neglect, but in given circumstances work against adolescents’ good health and welfare interests.

In sum, we note a mixed empirical picture of developments for key outcomes specifically also for underage youth through cannabis legalization in Canada. ¹ While reductions in cannabis use among adolescents have generally not occurred, developments for health-related outcomes are mixed and cannabis access has largely shifted from illegal to (while for legal-age adults) “legal” and/or “grey” sources. Conversely, the scope and burden of criminalization of adolescents for cannabis-related offences have been extensively reduced, while the presently remaining legal provisions for possible criminal charges for small amounts (>5 g) of cannabis and their ongoing, select enforcement appear to stand in conflict with the principal aims of protecting adolescents’ health and welfare. It warrants acknowledgement that reconciling underlying tensions between fundamental ideals and practical ways towards creating an “optimal” cannabis control approach for underage adolescents as a distinctly vulnerable group of concern—and especially so in “normalization” environments where cannabis use is explicitly legal for adults and a ubiquitously available consumption good—presents extraordinary if not impossible challenges. With these dynamics in mind, it is imperative going forward for key cannabis legalization-related indicators (including use levels, key health-related risk behaviours and/or outcomes, promotion exposure, sourcing, and enforcement) specifically for adolescents to be rigorously monitored. Such empirical information concerning this preeminent risk group will be crucial to identify essential needs and enable efforts towards reviewing and adjusting legalization and related regulation details in Canada as required for the effective protection of adolescents’ good health and welfare as a primary objective.