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A systematic review and Bayesian meta‐analysis of interventions which target or assess co‐use of tobacco and cannabis in single‐ or multi‐substance interventions
Author(s) -
Walsh Hannah,
McNeill Ann,
Purssell Edward,
Duaso Maria
Publication year - 2020
Publication title -
addiction
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.424
H-Index - 193
eISSN - 1360-0443
pISSN - 0965-2140
DOI - 10.1111/add.14993
Subject(s) - cannabis , psychological intervention , medicine , meta analysis , randomized controlled trial , smoking cessation , systematic review , psychiatry , medline , pathology , political science , law
Background and aims Tobacco and cannabis are commonly co‐used, and evidence for the influence of co‐use on quit outcomes for either substance is mixed. We sought to determine the efficacy of tobacco and/or cannabis use interventions delivered to co‐users on cannabis and tobacco use outcomes. Method Systematic review with meta‐analysis and narrative review, using five databases and author requests for co‐use data. Controlled and uncontrolled intervention studies focusing on treatment of tobacco and/or cannabis use assessing use of both pre‐ and post‐intervention were included. Prevention interventions were excluded. Bayesian meta‐analysis was used across four outcome measures: risk ratio for tobacco and cannabis cessation post‐intervention separately; standardized mean change for tobacco and cannabis reduction post‐intervention separately. Narrative reporting of the same outcome measures in non‐randomized clinical trials (non‐RCTs) and quality assessment of all included studies were conducted. Results Twenty studies (12 RCTs and eight uncontrolled) were included. Bayesian meta‐analysis with informative priors based on existing data of 11 RCTs (six single‐substance, five multi‐substance interventions) delivered to co‐users ( n = up to 1117) showed weak evidence for an effect on cannabis cessation [risk ratio (RR) = 1.48, credibility interval (CrI) = 0.92, 2.49, eight studies] and no clear effect on tobacco cessation (RR = 1.10, CrI = 0.68, 1.87, nine studies). Subgroup analysis suggested that multi‐substance interventions might be more effective than cannabis‐targeted interventions on cannabis cessation (RR = 2.19, CrI = 1.10, 4.36 versus RR = 1.39, CrI = 0.75, 2.74). A significant intervention effect was observed on cannabis reduction (ES = 0.25, CrI = 0.03, 0.45, nine studies) but not on tobacco reduction (ES = 0.16, CrI = −0.14, 0.45, nine studies). Quality of evidence was moderate, although measurement of co‐use and cannabis use requires standardization. Uncontrolled studies targeting both cannabis and tobacco use indicated feasibility and acceptability. Conclusions Single and multi‐substance interventions addressing tobacco and/or cannabis have not shown a clear effect on either tobacco or cannabis cessation and reduction among co‐users. However, dual substance interventions targeting tobacco and cannabis appear feasible.