Evidence That Cannabis Laws Reduce Opioid Problems Is Still Inconclusive | Research

The takeaway

A review of 21 studies examining whether cannabis laws affect opioid outcomes found largely inconclusive results, identifying six major research challenges that limit current evidence.

Cannabis policy researchers, opioid crisis stakeholders, public health policymakers

21 studies examined cannabis laws and opioid outcomes with largely inconclusive results

What the researchers found

Across 21 U.S. studies, results on whether cannabis laws reduce opioid prescribing, use, or mortality were largely inconclusive. Six key challenges were identified: inability to measure direct substitution, lack of individual-level longitudinal data, difficulty separating cannabis law effects from other policies, staggered implementation issues, limited consideration of specific law provisions, and insufficient data triangulation.

Why it matters

The popular narrative that cannabis legalization reduces opioid problems is not well supported by current evidence. Understanding the specific research gaps is essential before making policy claims about cannabis as an opioid substitute.

The numbers in context

21 studies reviewed; published 2014-2021; 6 research challenges identified; outcomes examined included opioid prescribing, use, use disorder, service utilization, and mortality; results largely inconclusive.

How the study worked

Narrative review of 21 U.S.-based studies published 2014-2021 examining associations between state medical and recreational cannabis laws and opioid-related outcomes.

What this study cannot tell us

Narrative rather than systematic review; limited to U.S. studies; rapidly evolving policy landscape means findings may become outdated; does not include studies published after 2021.

How to read the evidence

Narrative review identifying consistent methodological limitations across studies, providing moderate confidence in the assessment of evidence gaps.

When this study was published

Studies published 2014-2021.

The bigger picture

While there are theoretical reasons to expect cannabis laws could affect opioid outcomes, the current evidence base cannot reliably confirm or deny this relationship, and premature policy conclusions could be harmful.

Questions still open

Would individual-level longitudinal studies using multiple data sources provide clearer answers? Are specific cannabis law provisions (like allowing pain as a qualifying condition) more important than simple legal vs. illegal distinctions?

Common questions

Does cannabis legalization reduce opioid deaths?

The current evidence is inconclusive. While some studies suggest potential benefits, the review identified six major research challenges that prevent definitive conclusions about whether cannabis laws actually reduce opioid-related harms.

Why is the evidence so unclear?

Key challenges include the inability to directly measure whether people substitute cannabis for opioids, lack of individual-level data tracking people over time, and difficulty separating the effects of cannabis laws from other concurrent policy changes.

Read the original research

The state of the evidence on the association between state cannabis laws and opioid-related outcomes: A review.

Current addiction reports, 8(4), 538-545

View on PubMed ↗Publisher’s paper ↗

Citation

Tormohlen, Kayla N; Bicket, Mark C; White, Sarah; Barry, Colleen L; Stuart, Elizabeth A; Rutkow, Lainie; McGinty, Emma E. (2021). The state of the evidence on the association between state cannabis laws and opioid-related outcomes: A review.. Current addiction reports, 8(4), 538-545. https://doi.org/10.1007/s40429-021-00397-1