Daily Cannabis Use Was Linked to Slower Transition to Injection Drug Use in Street Youth
Street-involved youth who used cannabis daily were 34% less likely to start injecting drugs over a 10-year follow-up period, challenging the gateway drug hypothesis.
Quick Facts
What This Study Found
In a multivariable analysis, daily or more frequent cannabis use was associated with slower rates of injection drug initiation (adjusted hazard ratio 0.66, 95% CI 0.45-0.98). Sub-analyses showed this association was specific to injection stimulants, not injection opioids.
Key Numbers
481 youth followed over 10 years. 228 (47.4%) reported daily cannabis use. 103 (21.4%) initiated injection drug use. Adjusted hazard ratio for daily cannabis users: 0.66 (95% CI 0.45-0.98, p=0.038).
How They Did This
Prospective cohort study following 481 street-involved youth aged 14-26 in Vancouver, Canada from 2005-2015. Extended Cox regression with time-updated covariates examined factors associated with injection drug initiation.
Why This Research Matters
The gateway drug theory suggests cannabis leads to harder drugs. This longitudinal study found the opposite - daily cannabis use was associated with slower progression to injection drug use among a high-risk population, challenging a cornerstone of prohibitionist drug policy.
The Bigger Picture
As cannabis legalization expands, understanding its relationship to other drug use patterns becomes increasingly important. This study suggests that among high-risk youth, cannabis may serve as a substitute rather than a gateway to harder drugs.
What This Study Doesn't Tell Us
Observational study cannot prove causation. Self-reported drug use. Specific to street-involved youth in Vancouver, which may not generalize. Potential for unmeasured confounders.
Questions This Raises
- ?What mechanism might explain cannabis substituting for harder drugs?
- ?Why was the protective association specific to injection stimulants but not opioids?
- ?Would these findings replicate in other high-risk populations?
Trust & Context
- Key Stat:
- Daily cannabis users had a 34% lower rate of transitioning to injection drug use (adjusted HR 0.66).
- Evidence Grade:
- Moderate - large prospective cohort with 10-year follow-up and multivariable analysis, though observational.
- Study Age:
- Published in 2018. Data collected 2005-2015 in Vancouver.
- Original Title:
- Cannabis use is associated with lower rates of initiation of injection drug use among street-involved youth: A longitudinal analysis.
- Published In:
- Drug and alcohol review, 37(3), 421-428 (2018)
- Authors:
- Reddon, Hudson(5), DeBeck, Kora(8), Socias, Maria Eugenia(4), Dong, Huiru, Wood, Evan, Montaner, Julio, Kerr, Thomas, Milloy, Michael-John
- Database ID:
- RTHC-01807
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Is cannabis a gateway drug?
This 10-year study of high-risk street youth found the opposite pattern: daily cannabis use was associated with a 34% lower rate of starting injection drug use. The effect was specific to injection stimulants.
Does cannabis use lead to harder drugs?
Not in this study population. Street-involved youth who used cannabis daily were less likely to begin injecting drugs over the follow-up period. The researchers suggest cannabis may function as a substitute rather than a gateway.
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Cite This Study
https://rethinkthc.com/research/RTHC-01807APA
Reddon, Hudson; DeBeck, Kora; Socias, Maria Eugenia; Dong, Huiru; Wood, Evan; Montaner, Julio; Kerr, Thomas; Milloy, Michael-John. (2018). Cannabis use is associated with lower rates of initiation of injection drug use among street-involved youth: A longitudinal analysis.. Drug and alcohol review, 37(3), 421-428. https://doi.org/10.1111/dar.12667
MLA
Reddon, Hudson, et al. "Cannabis use is associated with lower rates of initiation of injection drug use among street-involved youth: A longitudinal analysis.." Drug and alcohol review, 2018. https://doi.org/10.1111/dar.12667
RethinkTHC
RethinkTHC Research Database. "Cannabis use is associated with lower rates of initiation of..." RTHC-01807. Retrieved from https://rethinkthc.com/research/reddon-2018-cannabis-use-is-associated
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.