Long-term observational studies of cannabis for chronic pain show modest benefits but very low evidence quality
A meta-analysis of six long-term observational studies found cannabis-based medicines produced modest pain reduction and some improvement in sleep for chronic non-cancer pain, but evidence quality was very low and nearly half of patients dropped out.
Quick Facts
What This Study Found
Mean pain reduction was 1.75 points on a 0-10 scale (95% CI 0.72-2.78). About 20.8% of patients reported ≥50% pain relief. Sleep improvements were moderate in effect size, while depression and anxiety improvements were small. Only 53.3% of patients completed the studies, with 6.8% dropping out due to adverse events.
Key Numbers
6 studies, 2,686 participants, 26-52 weeks duration. Pain reduction: 1.75/10. ≥50% relief: 20.8%. Study completion: 53.3%. Dropout from adverse events: 6.8%. Serious adverse events: 3.0%. Deaths: 0.3%.
How They Did This
Systematic review and meta-analysis of prospective observational studies with ≥26 weeks duration. Six studies with 2,686 participants were included. CENTRAL, EMBASE, and MEDLINE searched through December 2021. Random effects models used.
Why This Research Matters
While RCTs of cannabis for pain are typically short-term, these longer observational studies (26-52 weeks) provide a more realistic picture of sustained use, including the concerning finding that nearly half of patients discontinue treatment.
The Bigger Picture
The gap between enthusiasm for cannabis as a pain treatment and the actual evidence base remains wide. These long-term data suggest that while some patients benefit meaningfully, most do not achieve large improvements and many stop treatment.
What This Study Doesn't Tell Us
Very low certainty of evidence for all outcomes. Observational design without control groups. High dropout rates complicate interpretation. Heterogeneous pain conditions included. No standardized cannabis products across studies.
Questions This Raises
- ?Why do nearly half of patients drop out?
- ?Are there identifiable subgroups who respond well to long-term cannabis therapy?
- ?Would standardized products and doses produce better outcomes?
Trust & Context
- Key Stat:
- 21% of patients achieved ≥50% pain relief over 26-52 weeks
- Evidence Grade:
- Systematic review and meta-analysis, but all included evidence was rated very low quality.
- Study Age:
- Published in 2022 with studies searched through December 2021.
- Original Title:
- Long-term observational studies with cannabis-based medicines for chronic non-cancer pain: A systematic review and meta-analysis of effectiveness and safety.
- Published In:
- European journal of pain (London, England), 26(6), 1221-1233 (2022)
- Authors:
- Bialas, Patric(2), Fitzcharles, Mary-Ann(14), Klose, Petra(3), Häuser, Winfried
- Database ID:
- RTHC-03711
Evidence Hierarchy
Analyzes all available research on a topic using a structured method.
What do these levels mean? →Frequently Asked Questions
How much pain relief did cannabis provide on average?
Average pain reduction was 1.75 points on a 0-10 scale. About 1 in 5 patients (20.8%) achieved at least 50% pain relief, which is considered a clinically meaningful response.
How many patients continued treatment long-term?
Only 53.3% of patients completed the studies (26-52 weeks). About 6.8% dropped out specifically due to adverse events, with the rest discontinuing for other reasons.
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Cite This Study
https://rethinkthc.com/research/RTHC-03711APA
Bialas, Patric; Fitzcharles, Mary-Ann; Klose, Petra; Häuser, Winfried. (2022). Long-term observational studies with cannabis-based medicines for chronic non-cancer pain: A systematic review and meta-analysis of effectiveness and safety.. European journal of pain (London, England), 26(6), 1221-1233. https://doi.org/10.1002/ejp.1957
MLA
Bialas, Patric, et al. "Long-term observational studies with cannabis-based medicines for chronic non-cancer pain: A systematic review and meta-analysis of effectiveness and safety.." European journal of pain (London, 2022. https://doi.org/10.1002/ejp.1957
RethinkTHC
RethinkTHC Research Database. "Long-term observational studies with cannabis-based medicine..." RTHC-03711. Retrieved from https://rethinkthc.com/research/bialas-2022-longterm-observational-studies-with
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.