Prevalence of marijuana use does not differentially increase among youth after states pass medical marijuana laws: Commentary on Stolzenberg et al. (2015) and reanalysis of US National Survey on Drug Use in Households data 2002-2011

Melanie M. Wall, Christine Mauro, Deborah S. Hasin, Katherine M. Keyes, Magdalena Cerda, Silvia S. Martins, Tianshu Feng

Research output: Contribution to journalComment/debate

44 Scopus citations

Abstract

There is considerable interest in the effects of medical marijuana laws (MML) on marijuana use in the USA, particularly among youth. The article by Stolzenberg et al. (2015) "The effect of medical cannabis laws on juvenile cannabis use" concludes that "implementation of medical cannabis laws increase juvenile cannabis use". This result is opposite to the findings of other studies that analysed the same US National Survey on Drug Use in Households data as well as opposite to studies analysing other national data which show no increase or even a decrease in youth marijuana use after the passage of MML. We provide a replication of the Stolzenberg et al. results and demonstrate how the comparison they are making is actually driven by differences between states with and without MML rather than being driven by pre and post-MML changes within states. We show that Stolzenberg et al. do not properly control for the fact that states that pass MML during 2002-2011 tend to already have higher past-month marijuana use before passing the MML in the first place. We further show that when within-state changes are properly considered and pre-MML prevalence is properly controlled, there is no evidence of a differential increase in past-month marijuana use in youth that can be attributed to state MML.

Original languageEnglish (US)
Pages (from-to)9-13
Number of pages5
JournalInternational Journal of Drug Policy
Volume29
DOIs
StatePublished - Mar 1 2016

Keywords

  • Medical marijuana laws
  • Observational data analysis
  • Pre-post tests

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Health Policy

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