Tanis Cortens:
Though Trump is considering reclassifying marijuana with less dangerous substances such as testosterone and ketamine, strong evidence suggests the drug’s health risks are more significant than many realize. A November 2024 article in the American Journal of Public Health said cannabis use “can lead to a range of short- and long-term adverse cognitive, psychological, and physical outcomes.” Short-term harms include “impairments in memory, concentration, coordination, judgment, and reaction time as well as an increased risk of acute mood and anxiety disorders and psychotic episodes characterized by paranoia, delusions, and hallucinations;” long-term harms include “increased cardiovascular and pulmonary disease risk; pregnancy and neonatal outcomes such as premature birth, lower birth weight, and neonatal intensive care admissions; stunted brain development and longer-term cognitive impairment; lower educational attainment; diminished motivation and life satisfaction; and psychosis and psychotic disorders, such as schizophrenia.”
Addiction is also an issue. Yale Medicine defines cannabis use disorder (CUD) as “the continued use of cannabis despite significant negative impact on one’s life and health.” Roughly 10 per cent of those who begin smoking marijuana will develop an addiction, and 30 per cent of current users are considered addicted by the medical criteria. Furthermore, a January 2025 study in JAMA Psychiatry, published by the American Medical Association (AMA), found that CUD is not limited to recreational use; in fact, medical marijuana users were at least as likely to become addicted as were nonmedical users, if not more so. “These findings suggest that medically recommended cannabis is not associated with reduced addiction risk compared with nonmedical use,” wrote the researchers, quoted in a January 24, 2025 news article from United Press International. “Clinicians should consider addiction risk before recommending medical cannabis and, if they do, should monitor for CUD…emergence.”
Many of cannabis’s adverse effects are due to tetrahydrocannabinol (THC), the chemical that causes intoxication. The most common form of THC in the cannabis plant is delta-9 THC. According to the U.S. National Institute on Drug Abuse, the delta-9 THC potency in illegal cannabis seized by law enforcement increased from 3.96 per cent to 16.14 per cent between 1995 and 2022, and some products have THC concentrations above 40 per cent. Synthetic cannabinoids (SCs) are particularly dangerous in this regard: a June 2018 study published in Frontiers in Public Health found that SCs are stronger than organic cannabis and have greater psychoactive potential. “SC drugs show greater toxicity than organic cannabis,” concluded the article, “and therefore further investigation of their long-lasting and acute adverse effects is required as well as better detection and controlling measures against the spread of the use of SC products.”
In 2001, Canada became the first country to legalize medical marijuana, permitting patients to possess marijuana with a doctor’s signature. Bill C-45 passed in October 2018, making Canada the second country to legalize recreational marijuana for adults. (Uruguay alone had previously done so) Commercialization started in March 2020 when provinces began allowing the sale of more potent products beyond dried cannabis flower, such as edibles, vape pens, and concentrates.
An October 2023 study published in JAMA Network Open showed a connection between this commercialization and an increase in cannabis-attributable hospitalizations. The analysis of Canada’s four most populous provinces — Ontario, Quebec, Alberta, and British Columbia — found that commercialization was “associated with a significant immediate level change of 0.83…hospitalizations per 100, 000 individuals per month and an insignificant monthly slope increase of 0.02…hospitalizations per 100,000 individuals,” although the study is complicated by the overlap of the commercialization period studied (March 2020 to March 2021) and the COVID-19 pandemic. In contrast, the researchers saw a decline in cannabis-related hospitalizations in the period immediately after legalization (October 2018 to February 2020), likely due to the closure of illegal stores and the immaturity of the new legal market. Summing up, the authors wrote, “The findings in this study caution that greater levels of legal cannabis market access may be associated with an increase in a variety of cannabis-attributable harms.”
Marijuana’s impacts on developing brains are shown in an October 2024 meta-analysis of 63 studies including a total of 438,329 adolescents and young adults aged up to 24 years. Published in JAMA Pediatrics, the review “found moderate-certainty evidence that cannabis use during adolescence and young adulthood is probably associated with increased school absenteeism and dropout and reduced likelihood of obtaining high academic grades, graduating high school, enrolling in university, or postsecondary degree attainment. Low-certainty evidence suggests that cannabis use during adolescence and young adulthood may be associated with increased unemployment. More frequent cannabis use and earlier onset were associated with worse academic outcomes. Effective interventions to prevent early cannabis exposure are urgently needed,” concluded the authors.
According to the Ontario Poison Centre, some have been exposed to cannabis even earlier: “The Poison Centre is seeing an increase in cases of children unintentionally eating edible cannabis products and requiring hospital admission,” its website reads. “In many cases these products were unregulated, looked almost identical to popular brands of candy, and contained many more milligrams of THC than approved by Health Canada.…Any ingestion of cannabis in a child can cause serious harm.” Cannabis ingestion symptoms in children can include but are not limited to vomiting, slurred speech, drowsiness, slowed breathing, comas, and (rarely) seizures.
The website of the Government of Canada has a similar warning: “Hospitals have seen an increase in visits to the emergency room and poison centres have seen an increase in calls related to accidental poisonings from cannabis. Many cases involve kids under 12 years old, with most of these cases occurring in kids under the age of 5.”
Research conducted in 2021 by the Hospital for Sick Children (SickKids) showed “significantly higher rates of intensive care admission and more severe presentations to the SickKids Emergency Department (ED) for unintentional cannabis poisonings…following cannabis legalization in Canada.” Accidental poisonings in children under 12 quadrupled, and admissions to intensive care for severe poisoning tripled in the first two years after legalization. The study attributed this increase mainly to cannabis edibles, which are both highly potent and visually appealing to children.
Unintentional ingestion by children is not the only cause of marijuana-related hospitalizations: In addition to the aforementioned JAMA Network Open study, a September 2022 study in the same journal found that over seven-and-a-half years, rates of emergency department (ED) visits due to cannabis hyperemesis syndrome (CHS) increased 13-fold. The study’s authors wrote that CHS is “associated with persistent use of high potency cannabis (and) involv(es) repeated episodes of nausea, vomiting, and abdominal pain.”
Research published in Health Promotion and Chronic Disease Prevention in Canada (June 2025) showed a 120 per cent increase in cannabis-caused inpatient hospitalizations between 2007 and 2020. Cannabis-caused ED visits experienced a 113 per cent increase between 2007 and 2019, followed by a 12 per cent decrease in 2020. Overall, cannabis is Canada’s second most common reason for substance use-related hospitalizations as of November 2025, with alcohol remaining in the top spot.
Although deaths due to drugs are more often caused by toxic opioids and stimulants than by marijuana, Derek Lefebvre of the Canadian Institute for Health Information spoke to news outlet Press Progress on the importance of measuring marijuana-attributable hospitalizations. “There are costs and harms other than death,” he said in the November 6, 2025 article. “It’s causing a problem that they show up in hospitals, which isn’t good, and there are some associations with mental health, whether (cannabis is) the cause of or the symptom of mental health issues.”
Cannabis use may not result in as many fatalities as the use of other substances, but the possibility is still present; a retrospective study conducted in Ontario and published in April 2025 by the Recovery Research Institute examined the relationship between receiving hospital-based care for cannabis and an increased risk of death. The researchers found that “after adjustment for other confounding variables, the risk of death was still greater for people who received cannabis-related hospital-based care relative to the general population, with almost a 3-fold increased risk within 5 years for those who received hospital-based care.”
Scott Gottlieb, a senior fellow at the American Enterprise Institute and former head of the Food and Drug Administration, delivered some remarks on cannabinoids at Samford University McWhorter School of Pharmacy in September 2019. He expressed skepticism about marijuana’s supposed health benefits and advocated for an evidence-based approach to regulation. “Ultimately, we need to move past the social stigma around cannabis and address these complex public health and regulatory issues objectively,” he said. “If there’s a policy and regulatory framework under which certain products can be properly judged to be safe and effective based on sound scientific review, then we need to support these opportunities for patients. If the science demonstrates that there are risks associated with certain uses, we need to restrict the easy access. What we can’t do is let the development of an objective process for mediating these questions…be driven by the strong emotions on both sides of the cannabis debate. Our regulatory policy must follow the direction of sound science.”
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