Research Summary: Weeding out the truth

Weeding out the truth: a systematic review and meta-analysis on the transition from cannabis use to opioid use and opioid use disorders, abuse or dependence.
Link to paper published in Addiction: doi.org/10.1111/add.15581
The idea that cannabis is a ‘gateway drug’ to more harmful substances such as opioids is controversial. The 'gateway' theory has substantially impacted drug policy, education and how we conceptualise substance use.
Researchers at the Matilda Centre led a systematic review and meta-analysis on the transition from cannabis to opioid use. They found that there aren’t many good studies on the gateway drug theory.
The evidence available demonstrates that people who use cannabis are more than two times as likely to use opioids and develop opioid dependence. But the risk of bias and confounding factors need to be taken into account when looking at these results.
Citation:
Wilson J, Mills K, Freeman TP, Sunderland M, Visontay R, Marel C. Weeding out the truth: a systematic review and meta-analysis on the transition from cannabis use to opioid use and opioid use disorders, abuse or dependence. Addiction. 2022 Feb;117(2):284-298. doi: 10.1111/add.15581. Epub 2021 Jul 15. PMID: 34264545.