According to the results of a new research study, the number of seniors hospitalized for cannabis poisoning tripled after Canada legalized recreational cannabis use in 2018. The study, published in the journal JAMA Internal Medicine, has revealed that the number of individuals aged 65 and over checking into emergency rooms in Ontario due to cannabis-related poisoning has significantly increased over the last eight years.

Specifically, the study results show a spike in the number of ER visits for cannabis poisoning among seniors following the first phase of legalization, from 5.8 ER visits per 100,000, increasing to 15.4 per 100,000. Once edible cannabis products were legalized, the rate of cannabis-related poisoning among seniors increased again to 21.1 per 100,000. However, the study did not differentiate between poisonings due to intentional cannabis consumption, such as self-medication and recreational use, and unintentional consumption such as accidental ingestion.

Overall, the study shows that 2,322 emergency department visits over the eight-year span, which according to the study’s senior author, Dr. Nathan Stall, a geriatric specialist at Sinai Health in Toronto, are “relatively small numbers” compared to the approximately three million seniors in Ontario. In addition, Statistics Canada data shows that the rate of cannabis use among older Canadians is 7%, which is comparatively low in contrast to other other age groups.

“When you take edible cannabis and the drug effects are delayed for about three hours and you don’t feel anything after an hour, an hour and a half. They may be prone to take additional doses to try and reach that high,” said Dr. Stall in his interview with CTV News. “Once peak effect occurs, you have a phenomenon known as ‘dose stacking,’ where you’re stacking multiple doses together and that’s a contributor to poisoning.”

However, the study’s authors have also suggested that the results of the study may underestimate the number of cannabis poisonings in older adults, since the study only takes into account ER visits and has not examined the number of individuals who sought care elsewhere or not at all. 

A report published by Statistics Canada had previously shown that over 400,000 seniors reported using cannabis in the past three months in 2019, corresponding to a ten-fold increase from 40,000 seniors who reported using cannabis in 2012. Furthermore, more recent data shows that this trend has continued.

“Our findings align with national US data showing that edible cannabis accounts for an increasing proportion of cannabis poisoning in older adults,” states the study’s conclusion.  “Overall, this study shows the health outcomes of cannabis legalization and commercialization for older adults and highlights the consequences associated with edible cannabis? Jurisdictions with legalized cannabis should consider measures to mitigate unintentional exposure in older adults and age-specific dosing guidance.”