Monday, December 4, 2023
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Debunking claims about medical dagga use

Current international evidence does not support the hypothesis that SA legalising the use of dagga will cause more teens to use it, and will reduce the number of adults overdosing on opioids, which is a critical problem in the US, reports The Witness.

Since medical marijuana first became legal in California in 1996, it’s been legalised across nearly three-fifths of the US. However, that’s had virtually no impact on the rate of recreational marijuana use among teens, a broad review of published studies has found.

‘Several years ago, before the group of papers we (analysed) started to be published, people thought that US medical marijuana laws would increase teen marijuana consumption by ‘sending the message’ to teens that marijuana was safe and acceptable to use,’ explained Deborah Hasin, a professor of epidemiology at Columbia University’s College of Physicians and Surgeons in New York City, and the study’s lead author. Hasin however said: ‘It doesn’t seem that teens were impacted much by this – perhaps because they didn’t find the legalisation of medical use very relevant to them or didn’t even know about the laws.’

The report says South Africa’s recent court ruling refers to the use of dagga in private, not to the drug used medically and obtained in marijuana pharmacies, as in the US.

The report says a separate study team found the impact of marijuana legalisation also has been minimal on the risk for fatal overdosing among adult users of opioid pain medications. US, Australian and British researchers found little to suggest that increased access to medical marijuana as an alternative way to manage chronic pain has led to any measurable drop in deaths from opioid abuse.

Despite the findings of both research teams, legalising medical marijuana is not consequence-free, Hasin said. “Passing laws legalising marijuana use has some social benefits – business and tax revenues, job creation, and reduction in unfair race-based arrests,” she said. “And while not every marijuana user experiences harms, using marijuana does have some risks, including withdrawal, addiction and increased chances of vehicle crashes.”


In 1996, California became the first US state to legalise marijuana use for medical purposes. Opponents of medical marijuana argue that such laws increase recreational marijuana use among adolescents, while advocates contend that medical marijuana helps to address the US opioid crisis by reducing overdose deaths.

Two research papers look at the current evidence of the effects of medical marijuana laws and conclude that there is little support for either claim.

The first claim, that legalising medical marijuana increases recreational use among adolescents, is addressed by a new meta-analysis that pooled the results of eleven separate studies of data from four large-scale US surveys dating back as far as 1991. Results of the meta-analysis indicate that no significant changes (increases or decreases) occurred in adolescent recreational use following enactment of medical marijuana laws. Far fewer studies examined the effects of medical marijuana laws among adults, although existing evidence suggests that adult recreational use may increase after medical marijuana laws are passed

Hasin says: “Although we found no significant effect on adolescent marijuana use, we may find that the situation changes as commercialised markets for medical marijuana develop and expand, and as states legalise recreational marijuana use. However, for now, there appears to be no basis for the argument that legalising medical marijuana increases teens’ use of the drug.”

The second claim, that legalising medical marijuana reduces opioid overdose deaths by offering a less risky method of pain management, is addressed in an editorial co-authored by several members of Addiction’s editorial board. Here, the evidence is clear but weak, being rooted in ecological studies whose results have not been confirmed through more rigorous methods.

Although those studies show a correlation over time between the passage of medical marijuana laws and opioid overdose death rates, they do not provide any evidence that the laws caused the reduction in deaths. In fact, several recent studies have shown that chronic pain patients who use cannabis do not use lower doses of opioids. There are more plausible reasons for the reduction in opioid deaths that ought to be investigated.

Aims: To conduct a systematic review and meta‐analysis of studies in order to estimate the effect of US medical marijuana laws (MMLs) on past‐month marijuana use prevalence among adolescents.
Methods: A total of 2999 papers from 17 literature sources were screened systematically. Eleven studies, developed from four ongoing large national surveys, were meta‐analyzed. Estimates of MML effects on any past‐month marijuana use prevalence from included studies were obtained from comparisons of pre–post MML changes in MML states to changes in non‐MML states over comparable time‐periods. These estimates were standardized and entered into a meta‐analysis model with fixed‐effects for each study. Heterogeneity among the study estimates by national data survey was tested with an omnibus F‐test. Estimates of effects on additional marijuana outcomes, of MML provisions (e.g. dispensaries) and among demographic subgroups were abstracted and summarized. Key methodological and modeling characteristics were also described. Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines were followed.
Results: None of the 11 studies found significant estimates of pre–post MML changes compared with contemporaneous changes in non‐MML states for marijuana use prevalence among adolescents. The meta‐analysis yielded a non‐significant pooled estimate (standardized mean difference) of −0.003 (95% confidence interval = −0.012, +0.007). Four studies compared MML with non‐MML states on pre‐MML differences and all found higher rates of past‐month marijuana use in MML states pre‐MML passage. Additional tests of specific MML provisions, of MML effects on additional marijuana outcomes and among subgroups generally yielded non‐significant results, although limited heterogeneity may warrant further study.
Conclusions: Synthesis of the current evidence does not support the hypothesis that US medical marijuana laws (MMLs) until 2014 have led to increases in adolescent marijuana use prevalence. Limited heterogeneity exists among estimates of effects of MMLs on other patterns of marijuana use, of effects within particular population subgroups and of effects of specific MML provisions.

Aaron L Sarvet, Melanie M Wall, David S Fink, Emily Greene, Aline Le, Anne E Boustead, Rosalie Liccardo Pacula, Katherine M Keyes, Magdalena Cerdá, Sandro Galea, Deborah S Hasin

[link url=""]The Witness report (subscription needed)[/link]
[link url=""]Addiction Journal material[/link]
[link url=""]Addiction Journal abstract[/link]
[link url=""]Addiction Journal editorial[/link]

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