Friday, May 02, 2014

Prohibitionists keep flogging evidence-free fearmongering


(Email from Paul Desseaur)

Here’s a similar article;




Is there any evidentiary basis to these assertions?




Full text here;

<<< Analyzing data from the annual Monitoring the Future survey, Johnston et al

concluded that de-criminalization of marijuana in a number of states from 1975 to 1980 apparently had no effect on high school students’ beliefs and attitudes about marijuana or on their use of the drug during those years.

In contrast, Chaloupka et al, analyzing data from the 1992–1994 Monitoring the Future surveys,
found that “youths living in decriminalized states are significantly more likely to report currently using marijuana and may consume more frequently.”

There are several possible explanations for these disparate findings. >>>

Here’s the most likely explanation;

Johnston et al looked at 5 years data and saw no increasing trend in adolescent cannabis use, and no change in young peoples’ attitudes, in those states that decriminalised.

Meanwhile Chaloupka et al looked at two years data and compared states that had decriminalised with ones that hadn’t, and found a significant difference.

The findings of these two studies may not be contradictory at all; they are probably just a product of the fact that those states that first voted for medical marijuana laws, or to decriminalise cannabis use, were the states that already had the highest rates of use before they decriminalised.

The rest of the Pediatrics article discusses similarly contradictory evidence from differing jurisdictions, and the many confounders in attempting this kind of research.

The discussion is quite good, but the conclusions of this article are not very strongly supported by the evidence reviewed, and much of the concluding argument is based on inference and conjecture.

The other paper the authors reference to support the claim that decriminalisation will increase use amongst young people is this one;



2013 Overview; Key Findings on Adolescent Drug Use, Johnston et al, 2013;

It’s some great research, reviewing data from 1975 til last year.

But this is the only thing it says about adolescent cannabis use and legalisation of adult marijuana/medical marijuana use;

<<< Marijuana is one drug that is affected by some very specific policies, including medicalization and

legalization of recreational use by adults. The effects on youth behaviors and attitudes of recent changes in a number of states will need to be carefully monitored in future years.

Currently, marijuana does not hold the same appeal for youth as it did in the past, and today’s annual prevalance among 12th graders of 36% is considerably lower than rates exceeding 50% in the 1970s (documented by this project).

However, if states that legalize recreational marijuana allow marijuana advertising and marketing, then prevalence could rebound and approach or even surpass past levels >>>

Neither of these papers provides any evidence of youth attitudes changing, or young people’s cannabis use increasing, in any state when decriminalisation or MMLs have been introduced.

So, what actual evidence is available from those US states that have allowed medical cannabis use of any changes in young peoples’ attitudes to, or adolescents’ per-capita rates of, cannabis use, subsequent to the changes in the laws?

This large study compares rates in different states;

Choo et al 2011

<<< Based on their analysis of 32,570 students, they found that while marijuana use was common throughout the study period, there were no statistically significant differences in marijuana use between states where medical marijuana was legal and where it was illegal in any year. >>>

This compares young people exposed to MMLs both across states but also within the same state over time;

Effects of state medical marijuana laws on adolescent marijuana use. Lynne-Landsman et al, Am J PH, 2013;

<<< In 40 planned comparisons of adolescents exposed and not exposed to MMLs across states and over time, only 2 significant effects were found, an outcome expected according to chance alone. Further examination of the (nonsignificant) estimates revealed no discernible pattern suggesting an effect on either self-reported prevalence or frequency of marijuana use. >>>

This study analyses several years of data to compare rates of use before and after MMLs were introduced.

Yes, states with MMLs do have higher rates of adolescent cannabis use, but the higher rate predates the legal changes, and the changes had no discernible impact on young people’s perception of how safe or risky cannabis use was, and youth cannabis use actually slightly declined in those states with MMLs after the laws were introduced…

Do medical marijuana laws increase marijuana use? Replication study and extension. Harper et al, Ann Empidem, 2012;

<<< Difference-in-differences estimates suggested that passing MMLs decreased past-month use among adolescents by 0.53 percentage points (95% confidence interval [CI], 0.03-1.02) and had no discernible effect on the perceived riskiness of monthly use. Models incorporating measurement error in the state estimates of marijuana use yielded little evidence that passing MMLs affects marijuana use. >>>

Finally, this massive study examines trends over time within states that introduced MMLs, and also compares rates with similar states that did not…

The Impact of State Medical Marijuana Legislation on Adolescent Marijuana Use, Choo et al, JAH 2014;

<<<<<< The estimation sample was 11,703,100 students. Across years and states, past-month marijuana use was common (20.9%, 95% confidence interval 20.3–21.4). There were no statistically significant differences in marijuana use before and after policy change for any state pairing. >>>



<<< If Marijuana Legalization Sends The Wrong Message To Teenagers, Why Aren't They Listening?



“It’s time for prohibition supporters to stop hiding behind teens when debating marijuana policy.” >>>

See also;

<<< Legalizing medical marijuana doesn't increase use among adolescents.

Parents and physicians concerned about an increase in adolescents' marijuana use following the legalization of medical marijuana can breathe a sigh of relief. According to a new study at Rhode Island Hospital which compared 20 years worth of data from states with and without medical marijuana laws, legalizing the drug did not lead to increased use among adolescents. The study is published online in advance of print in the Journal of Adolescent Health.

"Any time a state considers legalizing medical marijuana, there are concerns from the public about an increase in drug use among teens," said principal investigator Esther Choo, M.D., an attending physician in the department of emergency medicine at Rhode Island Hospital. "In this study, we examined 20 years’ worth of data, comparing trends in self-reported adolescent marijuana use between states with medical marijuana laws and neighboring states without the laws, and found no increase in marijuana use that could be attributed to the law."





Paul Dessauer,

Outreach Coordinator, WASUA.

Email me at []

From: Update [] On Behalf Of Gary Christian
Sent: Thursday, 1 May 2014 7:38 AM
Subject: [Update] Legalization Harms Kids - Position Statement of Child Psychiatrists

The following article, which appeared in Psychiatric News today, points to an updated position statement by the American Academy of Child and Adolescent Psychiatry which opposes the legalization of marijuana for any purpose. The actual position statement follows. Monte

Legalizing Marijuana Could Harm Adolescents, Say Child Psychiatrists


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