No Strong Link Between Liberalization of Cannabis Policy and Teen Cannabis Use

Many countries are adopting increasingly lenient cannabis legislation. But some worry that as governments pass more liberal policies, more teens will be encouraged to experiment with cannabis. A new study refutes this claim.

The War on Drugs: More Harm Than Good

It’s been over 40 years since President Richard Nixon declared a “war on drugs.” This “war” has cost the United States nearly $1 trillion dollars. Millions of non-violent offenders are put behind bars every year. Yet there is little effect on the supply or demand for illegal substances.

Prohibitive cannabis legislation has been particularly harmful. Cannabis accounts for more than half of all drug arrests. This needlessly ensnares millions of otherwise law-abiding citizens in the criminal justice system and can affect a person’s ability to find housing, student aid, and employment.

Moreover, research into the therapeutic benefits of cannabis has been held back by decades due to prohibitive cannabis laws.

A New Peace

But there appears to be a light at the end of the tunnel.

After decades of prohibitive legislation, the global war on drugs looks like it might be winding down, especially when it comes to cannabis. More and more countries are adopting new laws to legalize the use of cannabis.

Here’s a list of countries that have legalized recreational cannabis:

  • Canada
  • Uruguay
  • South Africa
  • Georgia

And over 30 countries have legalized the use of cannabis for medicinal purposes. Some notable examples include:

  • Australia
  • Chile
  • Czech Republic
  • Germany
  • Italy
  • Portugal
  • Switzerland
  • Thailand
  • United Kingdom
  • New Zealand

Other countries have chosen to decriminalize cannabis or simply ignore existing laws that make it illegal.

Cannabis legalization appears to make sense from an economic standpoint. But could there be unintended consequences?

The Link Between Liberal Cannabis Policy and Teen Use

Many worry about the effect that more liberal cannabis policies could have on young people. They suggest that ending cannabis prohibition could lead to an increase in teen use.

The research gives mixed results. But one study has been repeatedly cited to support the association between a country’s cannabis policy and its rate of teen cannabis use.

The study, authored by Yayan Shi from the University of California San Diego, used survey data from 38 countries gathered by the World Health Organization.

The survey included questionnaire responses from teens around the world and was designed to estimate the national rate of cannabis use among young people.

The authors analyzed the survey data and concluded that countries with more liberal cannabis policies tended to have higher rates of teen cannabis use.

Problems with Data Interpretation

But one man was skeptical.

Alex Stevens is a professor at the University of Kent School of Social Policy, Sociology, and Social Research. Stevens carefully reviewed the numerical results presented by Shi’s study. He found they did not completely match the conclusions made by the author in the text of the study.

Stevens decided to take a closer look. He published the results in the International Journal of Drug Policy.

Reanalyzing the Data

He was able to get his hands on the raw survey data that Shi used. With the data in hand, he tried to reproduce Shi’s results using a similar method of analysis.

However, Stevens found several inconsistencies. For example, he couldn’t figure out how Shi reached their sample size number based on the factors they used to pick through the survey data.

Stevens decided to re-analyze the survey data using a slightly different method. He made two main changes.

First, he increased the sample size by including survey data that the Shi study left out from their analysis. For example, he included data from Sweden. This country was likely left out because the survey questions were coded a bit differently than other countries.

Second, he took into account the difference between genders when it comes to cannabis use. Boys tend to use cannabis at higher rates than girls, a variable that could affect the results of the analysis.

New Findings

When Stevens increased the sample size by including more available data and took into account the effect of gender on cannabis use, his results were quite different from Shi’s.

He found that there were was no statistically significant relationship between liberal cannabis policy and teen cannabis use.


It’s important to note that these findings do not completely refute a possible relationship between cannabis policy and cannabis use in teens. But it does show that an important piece of evidence for cannabis prohibition doesn’t stand up to more rigorous analysis.

The results are significant, as governments around the world are reconsidering how they deal with cannabis.

More research will bring more clarity and hopefully lessen unfounded fears. For example, one recent study refuted the long-held belief that cannabis use caused mental health issues and behavior problems in teens.

This also highlights the importance of open science. The researchers that collected the survey data used by Shi made it freely available. Without open access to that data, Stevens could not have taken a closer look at Shi’s findings.

This is especially important when it comes to interpreting large data sets. As we’ve seen here, different forms of analysis can give different results. But with an open model, researchers can hold each other accountable and try to improve their methods for testing a given hypothesis.

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