Systematic analysis of changes in cannabis use among participants in control conditions of randomised controlled trials

Rebgetz, Shane, Hides, Leanne, & Kavanagh, David J. (2015) Systematic analysis of changes in cannabis use among participants in control conditions of randomised controlled trials. Addictive Behaviors Reports, 1, pp. 76-80.

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Cannabis remains the most used illegal substance across the globe, and negative outcomes and disorders are common. A spotlight therefore falls on reductions in cannabis use in people with cannabis use disorder. Current estimates of unassisted cessation or reduction in cannabis use rely on community surveys, and few studies focus on individuals with disorder. A key interest of services and researchers is to estimate effect size of reductions in consumption among treatment seekers who do not obtain treatment. Effects within waiting list or information-only control conditions of randomised controlled trials offer an opportunity to study this question.


This paper examines the extent of reductions in days of cannabis use in the control groups of randomised controlled trials on treatment of cannabis use disorders. A systematic literature search was performed to identify trials that reported days of cannabis use in the previous 30 (or equivalent).


Since all but one of the eight identified studies had delayed treatment controls, results could only be summarised across 2–4 months. Average weighted days of use in the previous 30 days fell from 24.5 to 19.9, and a meta-analysis using a random effects model showed an average reduction of 0.442 SD. However, every study had at least one significant methodological issue.


While further high-quality data is needed to confirm the observed effects, these results provide a baseline from which researchers and practitioners can estimate the extent of change required to detect effects of cannabis treatments in services or treatment trials.

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ID Code: 91314
Item Type: Journal Article
Refereed: Yes
Keywords: cannabis, self-management, natural recovery, control conditions
DOI: 10.1016/j.abrep.2015.06.001
ISSN: 2352-8532
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Current > Schools > School of Psychology & Counselling
Copyright Owner: Copyright 2015 The Authors. Published by Elsevier B.V.
Copyright Statement: This is an open access article under the CC BY license (
Deposited On: 16 Dec 2015 01:28
Last Modified: 04 Apr 2017 07:14

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