Article Text

Download PDFPDF

Original research
Impact evaluations of drug decriminalisation and legal regulation on drug use, health and social harms: a systematic review
  1. Ayden I Scheim1,2,
  2. Nazlee Maghsoudi2,3,
  3. Zack Marshall4,
  4. Siobhan Churchill5,
  5. Carolyn Ziegler6,
  6. Dan Werb2,7
  1. 1Epidemiology and Biostatistics, Dornsife School of Public Health, Drexel University, Philadelphia, Pennsylvania, USA
  2. 2Centre on Drug Policy Evaluation, St Michael's Hospital, Toronto, Ontario, Canada
  3. 3Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
  4. 4Social Work, McGill University, Montreal, Quebec, Canada
  5. 5Epidemiology and Biostatistics, Western University, London, Ontario, Canada
  6. 6Library Services, Unity Health Toronto, Toronto, Ontario, Canada
  7. 7Medicine, University of California San Diego, La Jolla, California, USA
  1. Correspondence to Dr Dan Werb; dwerb{at}


Objectives To review the metrics and findings of studies evaluating effects of drug decriminalisation or legal regulation on drug availability, use or related health and social harms globally.

Design Systematic review with narrative synthesis.

Data sources We searched MEDLINE, Embase, PsycINFO, Web of Science and six additional databases for publications from 1 January 1970 through 4 October 2018.

Inclusion criteria Peer-reviewed articles or published abstracts in any language with quantitative data on drug availability, use or related health and social harms collected before and after implementation of de jure drug decriminalisation or legal regulation.

Data extraction and synthesis Two independent reviewers screened titles, abstracts and articles for inclusion. Extraction and quality appraisal (modified Downs and Black checklist) were performed by one reviewer and checked by a second, with discrepancies resolved by a third. We coded study-level outcome measures into metric groupings and categorised the estimated direction of association between the legal change and outcomes of interest.

Results We screened 4860 titles and 221 full-texts and included 114 articles. Most (n=104, 91.2%) were from the USA, evaluated cannabis reform (n=109, 95.6%) and focussed on legal regulation (n=96, 84.2%). 224 study outcome measures were categorised into 32 metrics, most commonly prevalence (39.5% of studies), frequency (14.0%) or perceived harmfulness (10.5%) of use of the decriminalised or regulated drug; or use of tobacco, alcohol or other drugs (12.3%). Across all substance use metrics, legal reform was most often not associated with changes in use.

Conclusions Studies evaluating drug decriminalisation and legal regulation are concentrated in the USA and on cannabis legalisation. Despite the range of outcomes potentially impacted by drug law reform, extant research is narrowly focussed, with a particular emphasis on the prevalence of use. Metrics in drug law reform evaluations require improved alignment with relevant health and social outcomes.

  • substance misuse
  • public health
  • law (see medical law)

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

View Full Text

Statistics from


  • Twitter @aydenisaac

  • Presented at Presented at the International Society for the Study of Drug Policy (May 22, 2019) and the International Harm Reduction Conference (April 29, 2019).

  • Contributors DW and AIS conceptualised and supervised the review. CZ designed and conducted the literature searches. AIS drafted the manuscript. SC, ZM and AIS conducted screening and data extraction. NM contributed to drafting the manuscript and developing figures. All authors contributed to interpretation of findings and revising the manuscript for important intellectual content.

  • Funding This review was supported by the Canadian Institutes of Health Research (CIHR) via the Canadian Research Initiative on Substance Misuse (SMN-139150), the MAC AIDS Foundation, and the Open Society Foundations. Ayden Scheim was supported by a Canadian Institutes of Health Research Postdoctoral Fellowship. Nazlee Maghsoudi is supported by a CIHR Vanier Canada Graduate Scholarship. Dan Werb is supported by a US National Institute on Drug Abuse Avenir Award (DP2- DA040256), a CIHR New Investigator Award, an Early Researcher Award from the Ontario Ministry of Research, Innovation and Science and the St Michael’s Hospital Foundation.

  • Map disclaimer The depiction of boundaries on the map(s) in this article does not imply the expression of any opinion whatsoever on the part of BMJ (or any member of its group) concerning the legal status of any country, territory, jurisdiction or area or of its authorities. The map(s) are provided without any warranty of any kind, either express or implied.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All relevant data are contained within the article and supplementary materials.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.