A systematic review and meta-analysis found that interventions for tobacco-cannabis co-users showed weak evidence for cannabis cessation and no clear effect on tobacco cessation, though cannabis use reduction was observed.
Addiction counselors working with co-users, researchers designing cessation interventions, and public health officials addressing dual substance use.
Multi-substance interventions doubled cannabis cessation odds (RR=2.19)
What the researchers found
Meta-analysis of 11 RCTs (up to 1,117 participants) showed weak evidence for cannabis cessation (RR=1.48, CrI 0.92-2.49) and no clear effect on tobacco cessation (RR=1.10, CrI 0.68-1.87). Multi-substance interventions appeared more effective for cannabis cessation than cannabis-only interventions (RR=2.19 vs. 1.39). A significant effect was found for cannabis reduction but not tobacco reduction.
Why it matters
Tobacco and cannabis are frequently co-used, and quitting one may be harder when still using the other. This review highlights that current interventions have limited effectiveness for co-users, signaling a need for better-designed dual-substance programs.
The numbers in context
20 studies included. 12 RCTs and 8 uncontrolled studies. Up to 1,117 participants in meta-analysis. Cannabis cessation RR=1.48. Tobacco cessation RR=1.10. Multi-substance interventions for cannabis cessation: RR=2.19.
How the study worked
Systematic review with Bayesian meta-analysis using informative priors. Five databases searched. 20 studies included (12 RCTs, 8 uncontrolled). Outcomes: cessation and reduction of both tobacco and cannabis.
What this study cannot tell us
Most included studies had small samples. Cannabis use measurement was not standardized across studies. Bayesian approach relies on prior assumptions. Moderate quality of evidence overall.
How to read the evidence
Systematic review with Bayesian meta-analysis of RCTs. Moderate quality evidence limited by small studies and unstandardized cannabis measurement.
When this study was published
2020 systematic review. First Bayesian meta-analysis specifically examining interventions for tobacco-cannabis co-users.
The bigger picture
As cannabis and tobacco co-use becomes better recognized as a clinical problem, developing effective interventions that address both substances simultaneously could improve outcomes for a large population of dual users.
Questions still open
- Why are multi-substance interventions better for cannabis but not tobacco cessation? Would tailored co-use interventions that address the specific interaction between tobacco and cannabis be more effective? How should success be measured in co-users?
Common questions
Is it harder to quit tobacco if you also use cannabis?
Should co-users try to quit both at once?
Read the original research
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.
Addiction (Abingdon, England), 115(10), 1800-1814
Citation
Walsh, Hannah; McNeill, Ann; Purssell, Edward; Duaso, Maria. (2020). 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.. Addiction (Abingdon, England), 115(10), 1800-1814. https://doi.org/10.1111/add.14993
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