Study: Marijuana’s Permanent Impact on the Developing Brains has been Overblown

John Rennie high school students in Montreal. (File image via The Canadian Press)

Marijuana and its effects on the developing brain is a highly contentious issue that has long been stifled by the lack of a clear scientific consensus to give a final say.

But a new study published on Wednesday in the journal JAMA Psychology found marijuana‘s “persistence and magnitude of impact” on teenagers had been exaggerated.

The new study reviewed and analyzed 69 cross-sectional pieces of research of 2,152 cannabis users and 6,575 comparison participants “showed a small but significant overall effect size for reduced cognitive functioning in adolescents and young adults who reported frequent cannabis use.”

However, after abstaining from cannabis for longer than 72 hours, the studies showed marijuana’s impact had “a very small, non-significant effect size.”

The study authors further explained that while there was “small reductions in cognitive functioning, results suggest that cognitive deficits are substantially diminished with abstinence.”

To read more about the study: Association of Cannabis With Cognitive Functioning in Adolescents and Young Adults.

The Study Could Influence Policymakers

The study could shed more light on this ongoing debate. It could also influence Canadian policymakers.

During one of his town hall meetings, Canadian Prime Minister Justin Trudeau, who won the 2015 elections, because he promised to legalize marijuana, himself said that cannabis can be “problematic” to the developing brain.

Canada's Prime Minister Justin Trudeau (C) poses for a selfie with students during the First Ministers' meeting in Ottawa, Canada November 23, 2015.
Canada’s Prime Minister Justin Trudeau (C) poses for a selfie with students during the First Ministers’ meeting in Ottawa, Canada November 23, 2015. (Image via Reuters)

In mid-March, Federal MP Bill Blair, who is tasked with leading the nationwide marijuana legalization, vowed to protect Canadian youth from organized crime, whom he said cash in about $20 million a day selling illicit cannabis.

Blair reiterated the government’s position on risks pertaining to youth consumption of marijuana, and how it could impair the “developing brain.” He said there are not only health risks but social dangers for the youth.

Their fear can explain why the new Cannabis Act could land offenders, who are illegally distributing or selling to the youth, up to 14 years in jail.

As Canada inches closer to a nationwide legalization, Canadian activists reject what they call a draconian law loaded with double standards, citing how alcohol is harmful to teens but violators don’t face a similar extreme predicament with the law. 

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Bill Blair speaks to Canadian at a town hall meeting about marijuana legalization in Toronto.

No Causality Link

The Canadian news station CBC is also throwing a free event in Vancouver on the eve of 4/20 to educate young Canadians about marijuana’s risks.

Meanwhile, University of British Columbia professor and researcher for the B.C. Centre on Substance Use, M-J Milloy, told CBC in an interview that there is no causality between cannabis and harming brain development for teens.

But he said there is an association.

For Zach Walsh, another UBC researcher specializing in cannabis, says: “The evidence is weaker than the rhetoric.”

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