A 4-year study found no evidence that cannabis improved pain or reduced opioid use in chronic pain patients | Research

The takeaway

Among 1,514 chronic pain patients on opioids, those who used cannabis reported greater pain severity, more anxiety, and lower confidence in managing pain over 4 years, with no evidence of opioid reduction.

Read this if you have chronic pain, use opioids, and are considering cannabis as a complement or alternative.

No evidence of opioid-sparing effect; cannabis users reported worse pain over 4 years

What the researchers found

This prospective national cohort followed 1,514 Australians with chronic non-cancer pain who were prescribed opioids over four years. Cannabis use was common and growing: by the four-year follow-up, 24% had used cannabis for pain and 60% expressed interest in using it.

The results challenged the narrative that cannabis helps chronic pain patients. Compared to non-users at four years, cannabis users had greater pain severity (both less frequent and daily users), greater pain interference with daily life, lower self-efficacy in managing pain, and higher anxiety scores.

Critically, the study found no evidence that cannabis use reduced prescribed opioid use or increased rates of opioid discontinuation. The hoped-for "opioid-sparing" effect of cannabis was not observed in this real-world cohort.

Temporal analyses confirmed there was no evidence that cannabis use preceded improvements in pain: the association between cannabis use and worse outcomes was consistent rather than reflecting a treatment response.

Why it matters

This is one of the largest and longest prospective studies of cannabis use in chronic pain patients on opioids. The findings directly counter the popular narrative that cannabis can replace opioids for chronic pain. While other study types have suggested opioid-sparing effects, this real-world longitudinal data found the opposite: cannabis users did worse across multiple outcomes.

The numbers in context

1,514 participants. 4-year follow-up. 24% used cannabis for pain by year 4. Interest in cannabis grew from 33% (baseline) to 60% (year 4). Cannabis users had greater pain severity: RR 1.14 (less frequent) and 1.17 (daily use). Greater pain interference: RR 1.21 and 1.14. Higher anxiety: RR 1.07 and 1.10. No evidence of opioid reduction.

How the study worked

The Pain and Opioids IN Treatment (POINT) study was a prospective national observational cohort. Participants were recruited through community pharmacies across Australia from 2012-2014 and followed with yearly interviews for 4 years. Logistic regression examined cross-sectional associations, and lagged mixed-effects models examined temporal relationships between cannabis use and outcomes.

What this study cannot tell us

This is an observational study and cannot prove that cannabis caused worse outcomes. People who use cannabis for pain may have more severe or refractory pain to begin with, explaining the worse scores. The study did not control for cannabis type, potency, or route of administration. Australian cannabis access differs from other countries. Self-selection bias could not be eliminated.

How to read the evidence

This is a large prospective national cohort with 4-year follow-up and appropriate statistical methods, providing strong evidence that challenges the opioid-sparing narrative.

When this study was published

Published in 2018 in The Lancet Public Health with data from 2012-2018. This remains one of the most cited studies questioning the opioid-sparing hypothesis.

The bigger picture

This study introduces important nuance to the cannabis-for-pain conversation. While preclinical and short-term clinical studies have suggested benefit, this long-term observational study of real patients found that those who chose to use cannabis did not fare better. This does not necessarily mean cannabis cannot help with pain, but it challenges the expectation that it will naturally reduce opioid use in this population.

Questions still open

Are the worse outcomes in cannabis users due to cannabis itself or to having more severe baseline pain? Would controlled cannabis administration (specific products, doses, and schedules) produce different results than self-directed use? Should the opioid-sparing narrative be revised based on this evidence?

Common questions

Can cannabis replace opioids for chronic pain?

This 4-year study of over 1,500 chronic pain patients found no evidence that cannabis reduced opioid use or improved pain outcomes. Cannabis users actually reported worse pain severity and more anxiety compared to non-users. However, this was observational and cannot rule out that specific cannabis-based treatments might help under different conditions.

Why did cannabis users have worse outcomes?

The study found cannabis users had greater pain severity, more pain interference, and higher anxiety. This could mean cannabis worsened their condition, or more likely, that people with more severe or difficult-to-treat pain were more likely to try cannabis. The observational design cannot determine which explanation is correct.

Read the original research

Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study.

The Lancet. Public health, 3(7), e341-e350

View on PubMed ↗Publisher’s paper ↗

Citation

Campbell, Gabrielle; Hall, Wayne D; Peacock, Amy; Lintzeris, Nicholas; Bruno, Raimondo; Larance, Briony; Nielsen, Suzanne; Cohen, Milton; Chan, Gary; Mattick, Richard P; Blyth, Fiona; Shanahan, Marian; Dobbins, Timothy; Farrell, Michael; Degenhardt, Louisa. (2018). Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study.. The Lancet. Public health, 3(7), e341-e350. https://doi.org/10.1016/S2468-2667(18)30110-5