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)
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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.
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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.
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