The decision to allow or not allow the use of cannabis for medical purposes in Canada is based on objective analysis of the facts, isn’t it? The truth may be surprising.

To begin with, it’s important to understand that the movement to control cannabis didn’t originate in Canada but stemmed from international bodies. By the 1890s, many western nations were concerned about the effects of the opium trade, as well as related narcotics such as cocaine and heroin. Cannabis, or “Indian hemp” as it was referred to, was of low priority, although the British government commissioned a report on its use and effects in India. The 1893/94 Indian hemp report (over 3,000 pages of it) is generally considered quite balanced, in that it concluded excessive use could be detrimental but was rare, while occasional or moderate use was probably safe and might even be “medicinal.”1

By the early 20th century, International Opium Convention meetings were held to tackle the trade in opium, heroin and cocaine. Cannabis was not included in the discussions until 1911, when a delegate from Italy, worried by hashish smuggling in Italian colonies in North Africa, suggested its inclusion. There was little support for this action but the American delegate suggested an addendum proposing further study into the issue.1

After World War I, the work of the International Opium Convention continued under the League of Nations. In its 1923 meeting, the delegate from Egypt gave an impassioned speech proposing that cannabis be included because it was “at least as harmful as opium, if not more so.” Delegates from countries with little or no experience with cannabis (which included Canada, the U.K. and U.S.) were left flat-footed and assumed countries where cannabis was common – such as Egypt, Turkey and Greece – had to know better than they did. So by the time the Geneva International Convention on Narcotics Control was signed in 1925, cannabis was included alongside opium and cocaine.1

Even before the Geneva International Convention was ratified, Canada had moved forward. In 1923, the Canadian government passed an Act to Prohibit the Improper Use of Opium and other Drugs. It has been claimed that cannabis was a last-minute addition to the list of prohibited drugs and if so, it’s unclear who added it, especially as it was not in popular use. A 1922 book The Black Candle by a judge, Emily Murphy, had a seven-page chapter called “Marahuana [sic] – a new menace” but there was no debate or discussion in the House of Commons, so whether this publication influenced policy is unknown.2

As we all know, this wasn’t the end of the story of cannabis in Canada. Recreational use of cannabis continued and increased over time, particularly after the 1960s, and a limited amount of research and treatment was conducted. Elsewhere, the use of cannabis for medical purposes began to emerge. For example, medical cannabis for cancer patients and others with pain-related illness was permitted in Israel starting in the early 1990s and California held a public referendum permitting its use in 1996. So even if medical cannabis was unavailable in Canada, people were hearing more and more about its use in other jurisdictions.

In 2000, the Ontario Court of Appeals ruled that the federal prohibition against medical cannabis breached the Canadian Charter of Rights and Freedoms by forcing a user to choose between his health needs and imprisonment.3 As a result of these and other constitutional challenges, the federal government was forced to rethink its medical cannabis policy and allow access for severely ill individuals.4 In 2001 the Medical Marihuana Access Regulations (MMAR) was established, under which people with specific severe or chronic medical conditions could receive authorizations from a physician to obtain cannabis directly from Health Canada, grow it themselves or have it grown by “designated” suppliers. The process was highly bureaucratic. It has been estimated that in the years immediately following its launch there were only a few hundred authorized users although between four hundred thousand and one million Canadians described themselves as “medical” cannabis users.3 The regulations were subsequently revised a number of time to improve the process, culminating in the Marihuana for Medical Purposes Regulations (MMPR) in 2014 and, as of 2017, the Access to Cannabis for Medical Purposes Regulations (ACMPR).

What is interesting in this saga is the almost complete absence of evidence to guide public policy. Neither the prohibition nor the legalization of cannabis for medical use grew out of a science-based examination of the facts by clinicians and scientists.

To protect the health of patients, ensure the efficient use of healthcare dollars, and promote the health and well-being of Canadians it’s essential that all decision on health and health care be based on the best-available and latest evidence. The Michael G. DeGroote Centre for Medicinal Cannabis Research is dedicated to ensuring that much-needed information on medical cannabis is developed, curated and made available for people, clinicians, scientists and policy-makers.

Author Details

The latest scientific evidence on this topic was reviewed by the Centre's leadership team. This evidence brief is written by Corinne Hodgson, DHealth, assessed for accuracy by Co-Director Dr. James MacKillop, PhD, an expert in addictions and mental health research. There are no conflicts of interest. Questions regarding this piece should be directed to Dr. James MacKillop (

  1. Brely-Taylor D, Blickman T, Jelsma M. The Rise and Decline of Cannabis Prohibition. The History of Cannabis in the UN Drug Control System and Options for Reform. 2014; Amsterdam: Transnational Institute

  2. Schwartz D. Marijuana was criminalized in 1923, but why? CBC News. Last Updated May 6, 2014.

  3. Paper: Medical Marihuana – Municipal Regulation of a Budding Industry. 07 Feb 2017 Wood Bull LLP.

  4. Fischer B, Kuganesan S, Room R. Medical Marijuana programs: Implications for cannabis control policy – Observations from Canada. Intern J Drug Policy 2015; 26:15-19