What is the relationship between medical cannabis legalization and opioid-related mortality?

The opioid epidemic, and related mortality that continues to sweep across much of the western world is likely to be abated only with a multi-faceted approach that offers improved regulation of industry practices, evidence-based prescribing practices and information for opioid users, curtailment of contraband product, expansion of harm reduction practices (such as safe injection sites), readily-available naloxone, and safer alternatives to pain management. Such multi-faceted approaches have been proposed¹² and progress is being made, in part, through a new set of prescribing guidelines developed under the auspices of the National Pain Centre located at McMaster University³. Furthermore, legally-available cannabis has emerged with enthusiastic endorsement among users for both pain relief, and the potential that it carries for reducing opioid-related mortality. However, a scarcity of high-quality research warrants caution regarding these potential benefits.

The prospects for reducing opioid-related mortality were suggested by an observational study⁴ showing a 25% reduction in opioid overdose mortality in US state jurisdictions that had legalized medical marijuana, relative to those that had not. Building upon this encouraging news, another observational study⁵ explored opioid-related deaths before and following the legal sale of cannabis for recreational purposes in Colorado. The investigators had the benefit of an extensive baseline period of fourteen years before the beginning of their post-legalization follow-up period of two years. The investigation found a statistically significant reduction in opioid-related mortality after legalization. Upon controlling for comparison state trends (using Nevada and Utah), and for administrative changes made to Colorado’s prescription drug monitoring program during the study period, the investigators found a 6.5% reduction in opioid-related mortality, or approximately 0.7 deaths per month, relative to baseline. This reduction translates into saving 8 or 9 deaths per year. However, it is equally important to note that the legalization of recreational cannabis in Colorado immediately brought to a halt that state’s fourteen-year trend of increasing deaths from opioids from approximately 31 deaths per month at the beginning of the year 2000 to approximately 75 deaths per month at the end of 2013. Upon the beginning of recreational cannabis legalization in January 2014, the monthly count immediately began to decline.

The investigators acknowledge that their study provides only the short-term (2 year) impact of cannabis legalization upon opioid-related mortality and encourage further exploration over longer time periods and in other jurisdictions. Nonetheless, if further evidence emerges, it may well be that medicinal cannabis becomes one of the tools used to fight the opioid epidemic.