The Hidden Risks of Cannabis Legalization: A Growing Public Health Concern

A study by leading research institutions highlights the adverse public health effects of cannabis legalization in Canada and the U.S., including increased adult use, child poisonings, mental health concerns, and cannabis-impaired driving. Researchers urge stricter regulations and ongoing monitoring to mitigate risks.

A groundbreaking study published in The Lancet Public Health by researchers from the University of Queensland, Ludwig Maximilian University, Simon Fraser University, and the University of Toronto examines the public health effects of non-medical cannabis legalization in Canada and the United States. The research provides an in-depth analysis of regulatory models, market dynamics, consumption patterns, and resulting health consequences. While legalization aimed to curb the illicit market, improve product safety, and generate tax revenue, its unintended health consequences are raising concerns. Increased availability, falling prices, and the proliferation of high-potency products have contributed to higher consumption rates and associated risks, prompting urgent calls for better regulation.

Following the legalization of cannabis in Colorado and Washington in 2014, 24 U.S. states have now allowed non-medical cannabis use, covering nearly half of the country’s population. Canada followed suit in 2018, implementing what was initially considered a more public health-oriented approach. However, both countries have witnessed similar trends—most notably an increase in frequent cannabis use among adults and growing concerns about its health effects. In the United States, surveys reveal that the number of daily cannabis users has risen sharply, surpassing the proportion of daily alcohol consumers. In Canada, national data shows that past-year cannabis use among adults grew from 14% in 2018 to 20% in 2020, with the most significant rise among individuals aged 25 to 44. Adolescent consumption, however, has remained relatively stable. Despite this, young people increasingly perceive cannabis as a low-risk substance, which could shape future usage trends.

Child Poisonings and Emergency Room Visits on the Rise

One of the most alarming consequences of legalization has been the surge in cannabis-related poisonings, particularly among children. The commercialization of cannabis-infused edibles—often resembling everyday candies, chocolates, and snacks—has resulted in a significant increase in unintentional ingestions. In Canada, emergency department visits for pediatric cannabis poisoning increased more than ninefold following the legalization of edibles in 2019. Similar patterns have been observed in the United States, where states that legalized recreational cannabis have reported rising poison control calls and hospital admissions for child cannabis exposure.

Adults, too, are experiencing adverse health effects from cannabis use. Emergency department visits for intoxication, hyperemesis syndrome, and cannabis dependence have significantly increased. Studies from Ontario indicate that while cannabis-related emergency visits initially declined immediately after legalization, they surged as more retail outlets opened. Similar trends have been observed across U.S. states with legal cannabis markets, raising concerns that the growing accessibility of high-potency cannabis products is leading to more severe health consequences.

Mental Health Concerns and Cannabis Dependence

The relationship between cannabis use and mental health remains a topic of significant debate. While research remains inconclusive, there is growing evidence of an increase in cannabis-induced psychosis, anxiety disorders, and depression. Emergency department visits for cannabis-related psychiatric symptoms have risen in some regions. In Ontario, visits for cannabis-induced psychosis initially declined post-legalization but spiked as the number of retail outlets expanded.

In the United States, studies exploring the connection between cannabis use and mental health disorders have produced mixed results. Some research suggests an increase in cannabis use disorder (CUD) in states with legal cannabis markets, while others indicate a decline in treatment admissions—possibly due to the removal of court-mandated rehabilitation programs. High-potency cannabis extracts and concentrates, some containing more than 70% THC, have been linked to a higher risk of dependence and psychiatric issues, prompting calls for stricter regulations on product potency and availability.

Cannabis-Impaired Driving: A Growing Concern

The impact of cannabis legalization on road safety remains controversial. Some studies indicate an increase in cannabis-related detections among fatally injured drivers, yet overall crash fatality rates have not shown consistent changes. In Canada, self-reported cannabis-impaired driving has slightly declined, but toxicology reports and emergency department data provide conflicting results.

While it remains unclear whether legalization has significantly increased impaired driving incidents, researchers stress the need for stronger enforcement of drug-impaired driving laws. Public education campaigns should also emphasize the risks of driving under the influence of cannabis, especially given the increasing availability of high-potency products that may prolong impairment.

Economic and Industry Pressures on Cannabis Regulation

Economic factors and regulatory challenges are shaping the future of cannabis legalization. Legal cannabis prices have fallen sharply—by as much as 50% in early-adopter U.S. states—making the drug more affordable and accessible. The legal market has introduced a broader range of high-potency products, including concentrates and edibles, further driving demand. While the cannabis industry claims that users self-regulate their THC intake, evidence suggests that stronger products increase the likelihood of dependence and psychiatric effects.

In both Canada and the U.S., the cannabis industry continues to lobby for deregulation, pushing for lower taxes and relaxed marketing restrictions. In the U.S., federal prohibition still limits interstate trade and banking access for cannabis businesses, but if cannabis is removed from the Controlled Substances Act, the industry could expand rapidly. In Canada, industry stakeholders are pressing for changes that would allow more aggressive advertising and branded packaging. If these lobbying efforts succeed, researchers warn that the trajectory of cannabis commercialization could mirror that of alcohol and tobacco, leading to higher consumption rates and greater public health risks.

Looking ahead, the full impact of cannabis legalization on public health may take decades to unfold. Chronic conditions linked to long-term cannabis use, such as cardiovascular diseases and certain cancers, may not become apparent for years. Furthermore, the long-term consequences of declining cannabis prices, increased product potency, and evolving consumption habits remain uncertain. The study underscores the need for continuous monitoring, urging governments to enforce stricter regulations on packaging, advertising, and THC limits to mitigate harm.

While legalization has significantly reduced cannabis-related arrests and eliminated criminal penalties, its broader health implications require careful scrutiny. Policymakers must strike a balance between economic benefits and public health priorities, ensuring that commercial interests do not overshadow the risks associated with increased cannabis use. The researchers emphasize the need for further studies, particularly longitudinal research on cannabis use patterns and health outcomes in both adolescents and adults, to guide evidence-based policymaking in North America and beyond.