WHO Updates Its Marijuana Report for the First Time in a Decade: “Most Marked in Jurisdictions That Allow the Commercialized Supply”
The World Health Organization published its first update on nonmedical marijuana since 2016 this week, and the new brief repeatedly ties rising harms to one thing: legal, commercial markets.
“The prevalence of the acute adverse effects of cannabis resulting in emergency department attendances has increased in jurisdictions that have legalized adult cannabis use,” the 19-page technical brief states. “These increases have been most marked in jurisdictions that allow the commercialized supply of cannabis.”
The pattern repeats across the document. Emergency department visits by children who ate marijuana edibles “in the belief that they are candies” have increased where nonmedical use is legal. Adolescents in those same jurisdictions now perceive marijuana as less risky. And more potent products are being sold in legal stores “at lower prices than was the case in illicit markets.”
WHO’s 2016 report made none of those findings, largely because in 2016 there was not yet a decade of legal retail to measure. Global use has grown over that span, from an estimated 181.8 million people in 2013 to 250 million in 2024.
On psychosis, the language firmed up. Evidence “has strengthened” that marijuana use is a “component cause” that interacts with other factors to precipitate schizophrenia or a psychotic disorder, with a dose-response relationship tied to both the frequency and the potency of adolescent use. The brief also addresses the industry’s most common rebuttal head-on: “Genetically informative studies suggest that the association between regular cannabis use and psychosis is not fully explained by shared genetic risks factors.”
That lands days after a landmark Australian-led meta-analysis of 149 studies and more than 70,000 people found marijuana users develop psychosis an average of two and a half years earlier than nonusers.
New to this edition is pregnancy. Citing a JAMA Pediatrics meta-analysis of 51 studies and 21.1 million participants, WHO reports moderate-certainty evidence that marijuana use in pregnancy is associated with low birth weight (odds ratio 1.75), preterm birth (1.52) and babies small for gestational age (1.57), plus lower-certainty evidence of greater perinatal mortality (1.29). Those associations persisted after adjusting for tobacco use.
“Patients are coming to me in their prenatal visits saying, ‘I quit smoking and drinking, but is it safe to still use cannabis?'” said lead author Jamie Lo, a maternal-fetal medicine physician at Oregon Health and Science University. “Until direct harms have been proven, they perceive it to be safe to use.” Lo recommends abstinence but advises harm reduction for patients who cannot stop.
The brief is not a policy document and says so: “This document is not normative in nature and does not intend to make recommendations.” It is a narrative review that does not grade the certainty of its evidence, and not every finding cuts the same direction. WHO now says long-term marijuana smoking “does not appear to produce” chronic obstructive pulmonary disease, and describes the increase in traffic injury risk as modest.
For public health professionals, the findings land as a caution. Where marijuana became a commercial product, WHO recorded more emergency department visits, more poisoned children and less perceived risk among teenagers. Those are the data now in front of the regulators, legislators and educators making the next round of policy and prevention decisions.