News Release

Cannabis-related emergency department visits increased significantly in Ontario after expansion of the cannabis retail market

Peer-Reviewed Publication

The Ottawa Hospital

A study published today in the journal Addiction examined cannabis-related emergency department visits in Ontario before and after the legalization of recreational cannabis in Canada in October 2018.

In the first six months after legalization, a government-controlled online agency was the only source of legal cannabis in Ontario. Between 7 and 18 months after legalization, there was a strict limit on the number of retail stores (a maximum of 67). In April 2020, the cap on stores was lifted resulting in an expansion to 742 stores (a 916% increase) over a 14-month period.

The study identified a large increase in the average number of emergency department (ED) visits per month attributed to cannabis by Ontario residents aged 15 and older.

The monthly number of emergency department visits attributed to cannabis increased by 190% over the whole study period from 555 visits in January 2016 to 1614 visits in May 2021.

Here’s a breakdown of the ED visits by key dates:

January 2016 (start of study; and prior to legalization): 555

September 2018 (1 month prior to legalization): 1,048 

February 2020 (end of capped market period): 1,179; a 12.5% increase compared to the month before legalization.

May 2021 (end of study during open market period): 1,614; a 54% increase compared to the month before legalization.

The monthly number of ED visits due to cannabis among individuals aged 15 to 24 years also increased by 36.2% between September 2018 (481) and May 2021 (655) suggesting that legalization may not be meeting one of its primary goals of reducing problematic use among youth.

In evaluating the health impacts of cannabis legalization, policy makers should be aware that cannabis use and related heath harms in Ontario have continued to increase over time and that greater clinical services and preventive policies may be indicated.

Author quotes:

“We saw much more frequent ED visits due to cannabis after recreational cannabis legalization and I am concerned that the rapid and ongoing expansion of the legal retail market may be a key contributor,” said lead author Dr. Daniel Myran, a family physician, public health and preventive medicine specialist, and postdoctoral fellow at the University of Ottawa, The Ottawa Hospital and ICES.  

“We found that health care visits due to cannabis did not increase much immediately after legalization – when there was a very limited legal cannabis market in Canada. Starting in early 2020 we saw large increase in visits when the legal market began expanding and the COVID-19 pandemic began.”

“The pandemic, a maturing legal market, or both could have played a role in the number of monthly ED visits due to cannabis in Ontario which has almost tripled over the past 5 years. Moving forward I think we need better access to treatment and a more public health-oriented approach to cannabis policy.”


“The association between recreational cannabis legalization, commercialization and cannabis attributable emergency department visits in Ontario, Canada: an interrupted time-series analysis” by Daniel Myran, Peter Tanuseputro, Michael Pugliese, Nathan Cantor, Emily Rhodes and Monica Taljaard, February16 2022.

About ICES
ICES is an independent, non-profit research institute that uses population-based health information to produce knowledge on a broad range of health care issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting health care needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners and practitioners to make decisions about health care delivery and to develop policy. In October 2018, the institute, formerly known as the Institute for Clinical Evaluative Sciences, adopted the initialism ICES as its official name. For the latest ICES news, follow us on Twitter @ICESOntario.

About The Ottawa Hospital 
The Ottawa Hospital is one of Canada’s top learning and research hospitals, where excellent care is inspired by research and driven by compassion. As the third-largest employer in Ottawa, our support staff, researchers, nurses, physicians, and volunteers never stop seeking solutions to the most complex health-care challenges. Our multi-campus hospital, affiliated with the University of Ottawa, attracts some of the most influential scientific minds from around the world. Backed by generous support from the community, we are committed to providing the world-class, compassionate care we would want for our loved ones.

Media contact:

Niveen Saleh

Director, Communications


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