“Legalize weed and more kids will start smoking dope.”
That’s the longstanding scare tactic voiced by anti-marijuana pundits. But how does it square with reality?
By cherrypicking the numbers, it’s possible to find specific places and time periods over the past 50 years when cannabis consumption by underage users has spiked. But, in almost all cases, these trends cannot be tied to legalization efforts. On the other hand, there is a voluminous body of research on the subject indicating that legalization has had minimal or no impact on the number of young adults consuming marijuana or on their frequency of use.
The latest and most comprehensive word on the subject comes from the National Bureau of Economic Research (NBER), which recently published a report titled, “The Public Health Effects of Legalizing Marijuana”. This report is based on a comprehensive review and analysis of multiple decades of data, with conclusions based on what the authors describe as the intention to “effectively communicate which studies should be taken seriously and which should be ignored.”
In addition to exploring general legalization-related trends such as availability, price, consumption, and public perceptions of marijuana, the authors devote a section of the report to the specific question of legalization’s effect on youth. The comprehensive references cited in their work allow us to take a deeper dive into the subject.
Youth Marijuana Use After Decriminalization
Early indications that legally available marijuana might not dramatically affect youth and young adult use patterns came with the first decriminalization efforts. The origin of marijuana decriminalization in the United States dates back five decades. In 1973, Oregon passed legislation reducing penalties for the possession of up to an ounce of marijuana down to a $100 civil fine.
Two years later, a study from the New York Academy of Sciences surveyed Oregon hospital records, reporting:
Medically significant problems from use of marijuana have decreased since decriminalization from 6.7% of drug-related admissions in 1970 to 2.5% in 1975.
The study also surveyed district attorneys, judges, police officers, and educators. While some law enforcement officers favored a return to criminal prosecution, educators generally reported that:
“[M]arijuana and especially other drug problems among students were on the decline.”
By the late 1970s, ten more states had decriminalized the possession of small amounts of marijuana. A study published in 1981 by the National Institute on Drug Abuse looked at marijuana use by high school seniors from the years 1975 to 1980 in states where marijuana had been decriminalized.
The authors write:
The preponderance of the evidence gathered and examined for this study points to the conclusion that decriminalization had virtually no effect either on the marijuana use or on related attitudes and beliefs about marijuana use among American young people in this age group. The degree of disapproval young people hold for marijuana use, the extent to which they believe such use is harmful, and the degree to which they perceive the drug to be available to them were also unaffected by the law change.
Marijuana Legalization Studies: Teens & Young Adults
Critics of marijuana legalization have argued that early studies such as those referenced above were flawed, as they were based on limited data and incomplete research designs. While there is some validity to such arguments, recent research based on a far broader body of evidence has generally supported earlier conclusions.
At the start of the 20th century, medical marijuana was legally available in only three states: California, Oregon, and Maine. Fast forward to 2023, and 37 states now support legal medical marijuana programs – with the majority of programs going into effect after 2010. Increasing availability has in turn sparked a growing body of research on the public health consequences of marijuana legalization.
The authors of the NBER study note:
Only four articles on this topic were published in 2013. By 2020, there were over 140 published articles relating to the legalization of marijuana and public health.
The studies deemed most credible by the authors of the new NBER report made use of what is known as difference-in-differences regression modeling, which is widely regarded as the most accurate method of identifying trends and outcomes from observational study data gathered over an extended period of time. A majority of the studies included in the NBER report based their research on the Youth Risk Behavior Surveys, which is a 30-year-plus national survey of health risks and behaviors among 9th to 12th grade students. Other longitudinal databases employed by studies referenced in the NBER report include the National Longitudinal Study Of Youth, the National Study On Drug Use And Health, and Monitoring the Future.
The most interesting takeaway from all of this data crunching is the similarity of conclusions. Of the 12 studies included in the assessment, ten reported that there was no evidence that decriminalization or legalization increased the likelihood of marijuana use or the frequency of use among teenagers.
One study, that is an outlier to the majority of literature, reported an increase in teen use following both medical and recreational marijuana legalization at a state level. A second study reported a spike in teen marijuana use between 2009 and 2013 due to changes in federal drug enforcement policies that de-prioritized the prosecution of medical marijuana users and producers. However, the same study noted a subsequent drop in teen use in the years after 2013.
More specific insights offered by the various studies include:
- Medical marijuana legalization resulted in a 9% decrease in the odds of marijuana use among teens
- There is no evidence that medical marijuana legalization affects teen-perceived riskiness of monthly marijuana use
- Medical marijuana legalization is associated with a 12% decrease in admission rates involving marijuana use among individuals under the age of 21 at publicly funded drug treatment facilities
- Recreational legalization resulted in an 8% decrease in the odds of any marijuana use and a 9% decrease in the odds of frequent teen marijuana use
- Recreational legalization is associated with a small decrease in the frequency of marijuana use among current marijuana users
Taken together, these studies present a generally reassuring picture that the legalization of medical cannabis does not increase marijuana use by teenagers. This finding is summed up nicely in a separate working paper from the National Bureau of Economic Research titled, “The Effects of Marijuana Liberalizations: Evidence from Monitoring the Future”, in which the authors state:
We find that marijuana liberalizations have had minimal impact on the examined outcomes. Notably, many of the outcomes predicted by critics of liberalizations, such as increases in youth drug use and youth criminal behavior, have failed to materialize in the wake of marijuana liberalizations.