“Street-involved youth are known to be at elevated risk of initiating injection drug use. However, the impact of so-called ‘gateway’ drugs, such as cannabis, on injection initiation is unknown.

The objective of this study was to examine the association between cannabis use and initiation of injection drug use among a prospective cohort of street-involved youth in Vancouver, Canada.

In a multivariable analysis, ≥daily cannabis use was associated with slower rates of injection initiation (adjusted relative hazard 0.66, 95% confidence interval 0.45-0.98; P = 0.038). Sub-analyses revealed that cannabis use was negatively associated with initiation of injection stimulants but not initiation of injection opioids.

DISCUSSION AND CONCLUSIONS:

Given the expansion of cannabis legalisation throughout North America, it is encouraging that cannabis use was associated with slower time to initiation of injection drug use in this cohort. This finding challenges the view of cannabis as a gateway substance that precipitates the progression to using harder and more addictive drugs.”

https://www.ncbi.nlm.nih.gov/pubmed/29430806

http://onlinelibrary.wiley.com/doi/10.1111/dar.12667/abstract