Is cannabis a “gateway drug” that increases the risk of young people trying more harmful substances?
Multiple studies have backed up the claim, including a 25-year study of adolescents that showed regular or heavy weed use increases chances of using other illicit drugs. But the long-held theory is controversial. Scientists are questioning whether other factors – such as trauma, homelessness and poverty – could be more significant contributing variables that weren’t taken into account in the original methodology.
That’s why researchers at BC’s Centre for Substance Use wanted to dig deeper into the relationship between cannabis use and, specifically, injectable drugs. From 2005 to 2015, a team led by research student Hudson Reddon tracked and interviewed 481 street-involved people between the ages of 14 and 26 who had reported using illicit drugs. Their research found daily cannabis use correlated to a 34 per cent decrease of the hazard rate – the number scientists calculated would normally try heroin or other injectable drugs for the first time.
"The decreased rate of injection initiation among frequent cannabis users challenges the claim of the gateway hypothesis that there is a causal link between cannabis use and initiation of subsequent so-called hard drug use," reads the study, published in the March issue of the Drug and Alcohol Review.
There have been two other studies that have examined cannabis use and its relationship to using injectable drugs for the first time, with very different results: in Baltimore, a study showed weed use was associated with first-time injections. Another Vancouver study showed the opposite – that it decreased the risk of injecting drugs.
But why? The authors theorize that there's more to it than cannabis use.
The @PHAC_GC report on #OpioidCrisis is out, & tragically #vancouver accounted for nearly 10% of 4000 deaths in Canada in 2017.But @VanFireRescue @IAFF18 & partners incl @BC_EHS @VancouverPD #frontlineworkers SAVE 28 OF EACH 29 OPIOID OD’s in #DTES! https://t.co/I2rvviBCHX pic.twitter.com/ZFsRjxU7wk
— Darrell Reid (@FireChiefReid) March 30, 2018
"An analysis of nationally representative data from 17 countries demonstrated that the association between cannabis use and subsequent illicit drug use was weaker in countries with higher rates of cannabis use, suggesting that drug use progressions may be moderated by drug prevalence and social acceptability of certain substances,” reads the study.
— Vancouver Courier (@VanCourierNews) March 9, 2018
The authors also report that tetrahydrocannabinol (THC) and cannabinol (CBD) have reduced cocaine cravings in rats – pointing to the potential for cannabis to be used in addiction treatment for more addictive and damaging illicit drugs. But rats aren’t humans, and the authors call for more human trials to further investigate its potential.
In 2017, Canadian researchers also published a study on 122 subjects in Vancouver over a three-year period that found intentional use of cannabis consumption to curb crack cocaine cravings resulted in reduced usage. "Given the substantial global burden of morbidity and mortality attributable to crack cocaine use disorders alongside a lack of effective pharmacotherapies," the researchers wrote in the journal Addictive Behaviors. "We echo calls for rigorous experimental research on cannabinoids as a potential treatment for crack cocaine use disorders."
It all adds up to a timely reevaluation of the pro-prohibition argument as Canada prepares to finally end that approach to cannabis after nearly a century.
"Given the expansion of cannabis legalization throughout North America, it is encouraging that cannabis use was associated with slower time to initiation of injection drug use in this cohort,” the BC scientists concluded their 2018 study. "This finding challenges the view of cannabis as a gateway substance that precipitates the progression to using harder and more addictive drugs."
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