In a French cohort of 29,393 teenagers, daily cannabis users were 124 times more likely to initiate other illicit drugs than non-users, after adjusting for tobacco and alcohol.
Read this if you want to see the quantitative data on how cannabis use relates to other drug experimentation.
124x higher risk of trying other drugs for daily cannabis users
What the researchers found
Using a retrospective cohort of 29,393 French teenagers, researchers modeled all possible pathways from initial abstinence through cannabis initiation, daily cannabis use, and other illicit drug (OID) initiation using a Markov multi-state model.
The risk of initiating other illicit drugs was 21 times higher among cannabis experimenters and 124 times higher among daily cannabis users compared to non-users, after adjusting for tobacco and alcohol use. Tobacco and alcohol use also increased the risk of progressing to cannabis use.
The authors suggested OID experimentation could be a consequence of opportunity: once someone uses the most accessible illicit drug (cannabis), they gain access to social networks and markets where other drugs are available.
Why it matters
The 124-fold increase for daily users was striking and provided quantitative support for stage-based drug use progression. The opportunity-based explanation (access to drug networks) offered a more nuanced view than simple pharmacological gateway theories.
The numbers in context
29,393 teenagers. Cannabis experimenters: 21x higher OID risk. Daily cannabis users: 124x higher OID risk. Tobacco initiation HR=1.2, daily tobacco HR=2.6, drunkenness HR=2.8 for cannabis progression.
How the study worked
Retrospective cohort of 29,393 French teenagers. Markov multi-state model modeled all pathways from abstinence through cannabis stages to other drug initiation. Adjusted for tobacco and alcohol use as transition modifiers.
What this study cannot tell us
Retrospective self-report data. French teenager population may not generalize globally. The 124-fold increase, while large, may partly reflect selection effects (people who use cannabis daily are different from non-users in many ways). Cannot prove causation despite the multi-state modeling approach.
How to read the evidence
Large retrospective cohort with sophisticated multi-state modeling and adjustment for confounders. Strong for quantifying associations but cannot prove causation.
When this study was published
Published in 2012. The stage model of drug use progression continues to be debated and studied.
The bigger picture
This study modeled the entire sequence of drug use progression, going beyond simply asking "does cannabis lead to other drugs?" to quantifying the risk at each stage. The dose-response relationship (experimenters vs daily users) strengthened the association.
Questions still open
- Would delaying cannabis initiation reduce other drug use? Does the opportunity hypothesis mean regulated cannabis markets could reduce the gateway effect? Is the 124-fold increase an artifact of the population most likely to use any drug?
Common questions
Does cannabis really lead to harder drugs?
Could legal cannabis reduce the gateway effect?
Read the original research
Cannabis use stages as predictors of subsequent initiation with other illicit drugs among French adolescents: use of a multi-state model.
Addictive behaviors, 37(2), 160-6
Citation
Mayet, Aurélie; Legleye, Stéphane; Falissard, Bruno; Chau, Nearkasen. (2012). Cannabis use stages as predictors of subsequent initiation with other illicit drugs among French adolescents: use of a multi-state model.. Addictive behaviors, 37(2), 160-6. https://doi.org/10.1016/j.addbeh.2011.09.012
Explore the wider topic
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