Home > Effects of legalizing cannabis. Technical report.

Manthey, Jakob and Hayer, Tobias and Jacobsen, Britta and Kalke, Jens and Klinger, Sinja and Rehm, Jürgen and Rosenkranz, Moritz and Verthein, Uwe and Wirth, Marielle and Armstrong, Michael and Myran, Daniel T and Pacula, Rosalie and Queirolo, Rosario and Zobel, Frank (2023) Effects of legalizing cannabis. Technical report. Hamburg: “Institut für interdisziplinäre Sucht- und Drogenforschung (ISD).

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Based on the coalition agreement of the governing parties from November 2021, the German government plans to legalize the consumption of cannabis for recreational purposes. The intention of this initiative is to control the quality of the drug, to prevent the transfer of contaminated substances, and to guarantee the protection of minors. Key points of this project were worked out in October 2022 and submitted to the EU Commission for review. The introduction of the legal and controlled cannabis distribution to adults will be aimed at improving the protection of youth, the health of consumers, and at curbing and preventing the black market.


To substantiate the achievability of these goals, a study was commissioned to show the current state of research on the effects of the controlled distribution of cannabis based on an international literature review and input from experts in the field. For this purpose, the scientific findings and experiences in countries that have regulated and decriminalized not only the possession and cultivation of cannabis for personal use, but also the commercial production and distribution of recreational cannabis, as well as in countries that have implemented other forms of legalization (such as the release of possession and cultivation for personal use) should be examined. These countries include, for example, Canada, Uruguay, several US states, Switzerland, and the Netherlands.


This project seeks to provide answers to the following eight questions: 

  • 1) How did public health indicators (e.g., morbidity, cannabis use disorders, addiction treatment, prevention) change in legalizing countries? 
  • 2) What do we know about the development of cannabis use (prevalence) in legalizing countries (compared to pre-legalization)? 
  • 3) How did the protection of youth (e.g., availability of and exposure to cannabis, use trajectories, prevention, morbidity, cannabis use disorders) change in legalizing countries? Which accompanying measures have been proven successful to protect minors? 
  • 4) In legalizing countries, which regulations have had positive effects on protecting youth and public health? Which regulations had negative effects? Of particular interest are limits of THC concentration and minimum legal purchasing age. 
  • 5) In legalizing countries, was the illegal market successfully reduced? If yes, to which degree? Is there an association between the degree of reduced illegal market and regulations, such as upper limits for THC concentration, allowing legal sales of edibles, or allowing online purchases? 
  • 6) How have organized crime activities in relation to cannabis changed in legalizing countries? 
  • 7) In legalizing countries, is there a quantifiable association between the price of legal recreational cannabis and the share of the illegal market? 
  • 8) Which statutory regulations have been issued to avoid interactions between legal and illegal markets? How did these regulations affect the illegal market? Of particular interest are regulations concerning the documentation of the different steps in the supply chain (from seed to sale) and access to the market (licensing models) in legalizing countries.

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