How Does Cannabis Use Affect Heroin Use Disorder?

Cannabis use is prevalent among individuals with opioid use disorder, but the nature of its association with illicit opioid use remains unclear. A recently published study aims to shed light on the complex relationship between cannabis and heroin use over an extended period, spanning 18 to 20 years, addressing limitations identified in previous research with shorter follow-up durations.

The Australian Treatment Outcome Study (ATOS) enrolled 615 individuals with heroin dependence in 2001 and 2002. Follow-up interviews were conducted at 3, 12, 24, and 36 months, as well as 11 and 18–20 years after baseline. Opiate Treatment Index was utilized to assess heroin and cannabis use at each time point. A random-intercept cross-lagged panel model analysis was employed to discern within-person relationships between cannabis and heroin use during subsequent follow-ups.

Once demographic variables, other substance use, and mental and physical health measures were factored in, something caught the researchers' eyes. An uptick in cannabis use 24 months after the baseline was notably linked to a subsequent rise in heroin use at the 36-month mark (estimate=0.21, SE=0.10).

Hold on, it's a two-way street. Increased heroin use at 3 and 24 months, on the other hand, correlated with a decrease in cannabis use at 12 months (estimate=−0.27, SE=0.09) and 36 months (estimate=−0.22, SE=0.08). Interesting, right?

But before we jump to conclusions, let's pump the brakes. All the other cross-lagged associations? Not significant. It seems the relationship between cannabis and heroin use is a bit like catching fireflies – sporadic and elusive.

So, what's the big takeaway?

Well, despite some sparks of correlation in the early stages, the overall evidence isn't strong enough to confidently claim a one-way or two-way street between these substances. It's a reminder that the intricacies of this relationship might need a more nuanced lens.

This study acts as a beacon, highlighting the importance of comprehensive, long-term research to truly grasp the dance between cannabis and heroin use in individuals dealing with opioid use disorder. For now, it appears that evidence for any positive or negative relationship is lacking. So much for all the hype and optimism surrounding cannabis potential in curbing heroin addiction?