Canada’s largest clinical trial: Marijuana legalization 2018

Issue: BCMJ, vol. 59, No. 8, October 2017, Pages 395-396 Letters

In the past year, many news stories, peer-reviewed articles, and opinion pieces have debated how eased restrictions on marijuana possession and use stand to affect the lives of Canadians.

In the past year, many news stories, peer-reviewed articles, and opinion pieces[1] have debated how eased restrictions on marijuana possession and use stand to affect the lives of Canadians. This topic is of keen interest to the public and it would seem that everyone has an opinion on how accessible marijuana will reshape the economy and health outcomes, particularly among underserved and vulnerable populations. Members on either side of the debate have substantiated their arguments with those of politicians, doctors, and other leaders who regularly weigh in on marijuana legalization. At first, it may seem prudent to base our own arguments on those of leaders in the field; however, we do not recognize that many of the opinions of such experts are precisely that—views and opinions—which themselves have yet to be systematically validated at a national level.

Historically, federal restrictions on studies evaluating the economics and health effects of controlled substances, such as marijuana, have hampered our understanding of such substances.[2] Extrapolating risks and benefits of marijuana legalization within discrete populations where marijuana is already legal (e.g., Colorado) is fraught with bias, and much of the data for measuring long-term consequences of marijuana legalization remain immature.[3] As such, we are all blind when it comes to accurately predicting how the new laws will shape our country (if at all).

Regardless of whether marijuana legalization will increase the incidence of psychosis among teenagers while simultaneously undermining the marijuana black market, with certainty, we must be prepared to study these consequences. This means that before royal assent of Bill C-45 we have comprehensively outlined ways to evaluate how marijuana will affect Canada and its people. This means ensuring we have detailed baseline characteristics on marijuana usage associated with mental health, fatalities, and organized crime, among other measures. This means mobilizing funds and researchers who will be unhindered in studying the immediate and long-term effects of marijuana legalization. Given the widespread use of nonmedicinal marijuana in Canada, in effect, we must be ready to capitalize on studying the largest clinical trial of the century in this country.[4]

Recently, the timeline of marijuana legalization has come into question.[5] I have faith that we will be prepared if the Canadian Centre on Substance Abuse[6] maintains its commitment to objectively and transparently monitoring, the effects of marijuana legalization and further, if legislators are willing to act on findings from this and other research groups.
—David D.W. Twa, BSc
MD/PhD Candidate, UBC, Class of 2021

This letter first appeared as a post on the BCMJ blog.


1.    Kelsall D. Cannabis legislation fails to protect Canada’s youth. CMAJ 2017;189:E737-738.
2.    Allen K. As legal weed looms, barriers to research still standing. The Toronto Star. 9 April 2017.
3.    Aydelotte JD, Brown LH, Luftman KM, et al. Crash fatality rates after recreational marijuana legalization in Washington and Colorado. Am J Public Health 2017;107:1329-1331.
4.    Canadian Centre on Substance Abuse. Clearing the smoke on cannabis. Updated September 2016.
5.    Harris K. Federal-provincial showdown looms over legal pot deadline. CBC News. 19 July 2017.
6.    Canadian Centre on Substance Use and Addiction. National research agenda on the health impacts of non-medical cannabis use. Accessed 8 September 2017.

David D.W. Twa, BSc. Canada’s largest clinical trial: Marijuana legalization 2018. BCMJ, Vol. 59, No. 8, October, 2017, Page(s) 395-396 - Letters.

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