Marijuana legalization is not associated with higher teenage use, new study claims

With a growing body of evidence confirming the potential harm marijuana can cause on a growing adolescent brain, it is reasonable to ask what governmental policy best reduces teenage consumption. A new study has concluded that tough marijuana laws are not associated with reduced teenage use and the current wave of legalization does not seem to increase adolescent consumption.

Alongside Canada, Uruguay and a multitude of American states, marijuana legalization seems to be a trend rapidly spreading across the globe. New Zealand is set for a referendum on the issue in 2020, and the Mexican supreme court recently laid the foundation for legalization in the country potentially quite soon.

A big question that is rightly asked surrounding marijuana legalization is whether lifting the prohibition on the drug will result in greater youth consumption, a reasonable concern considering the science suggesting it may cause long-term damage to growing adolescent brains. A key study from 2015, led by Yuyan Shi from the University of California San Diego, has underpinned a large volume of calls to restrict the spread of marijuana legalization. That research pooled data from 38 countries and over 150,000 adolescents with an average age of 15. The study concluded a significant association between higher levels of youth marijuana use and more liberal policies such as depenalization and partial-prohibition.

Inspired by a raft of newer research suggesting no association between legalization and increased adolescent use, Alex Stevens, from the University of Kent, set out to re-examine the 2015 study's conclusions to ascertain its veracity. Stevens attempted to replicate the same pool of data the earlier study utilized, but included a number of variables and amendments, such as additional survey data from Sweden and a re-interpretation of the influence gender has on cannabis use in different countries.

"Shi et al's verbal summary of their findings is not supported by detailed interpretation of their own numerical results," Stevens writes in his research paper. "Without making the suggested amendments, it is possible to find a statistically significant association between policy 'liberalization' and higher odds of some measures of adolescent cannabis use. But when these improvements are made, this association becomes statistically non-significant."

Stevens' conclusion is interestingly backed up by smaller studies looking at the first few years of legalization in some early adopting American states. The suggestion is that full prohibition does not reduce youth consumption rates in comparison to full legalization and Stevens suggests, in light of this fact, that the social harm of marijuana criminal convictions may be more damaging to a community.

"My new study joins several others which show no evidence of a link between tougher penalties and lower cannabis use," explains Stevens. "This is useful information for governments as they consider the best way to deal with cannabis. As it is, the harms and costs of imposing criminal convictions on people who use cannabis do not seem to be justified by an effect in reducing cannabis use."

The new study was published in the International Journal of Drug Policy.

Source: University of Kent