Smoked Cannabis Reduces MS Spasticity but Impairs Cognition
What Researchers Found About Spasticity and Cannabis
The Study at a Glance
Published
CMAJ, 2012
Researchers
University of California San Diego (USA)
Study Type
Randomized Controlled TrialParticipants
37 patients · 3 days per period (crossover)
Key Finding
Smoked cannabis was superior to placebo in symptom and pain reduction in participants with treatment-resistant spasticity. Future studies should examine whether different doses can result in similar beneficial effects with less cognitive impact.
Key Finding: Smoked cannabis was superior to placebo in symptom and pain reduction in participants with treatment-resistant spasticity. Future studies should examine whether different doses can result in similar beneficial effects with less cognitive impact.
What Researchers Studied About Spasticity and Cannabis
Spasticity is a common and poorly controlled symptom of multiple sclerosis (MS).
This was a placebo-controlled, crossover trial in adult patients with MS and spasticity.
Researchers aimed to determine the short-term effect of smoked cannabis on spasticity.
How This Randomized Controlled Trial Was Conducted
37 participants were randomized; 30 completed the trial.
Participants were assigned to either smoked cannabis (once daily for 3 days) or identical placebo cigarettes (once daily for 3 days).
After a washout interval of 11 days, participants crossed over to the opposite group.
Primary outcome: change in spasticity on the modified Ashworth scale. Secondary outcomes: pain (visual analogue scale), timed walk, cognitive function (PASAT), and fatigue.
Spasticity Treatment Results
The Main Results:
- 1Smoked cannabis reduced Ashworth spasticity score by 2.74 points MORE than placebo (P < 0.0001)
- 2Smoked cannabis reduced pain VAS by 5.28 points MORE than placebo (P = 0.008)
- 3Timed walk: NO significant difference (P = 0.2)
- 4Cognitive function (PASAT): DECREASED by 8.67 points MORE with cannabis (P = 0.003) - NEGATIVE
- 5No serious adverse events occurred during the trial
- 637 randomized, 30 completed
By the Numbers
| Statistic | What It Means |
|---|---|
| P < 0.0001 | Highly significant reduction in spasticity with smoked cannabis vs placebo |
| 2.74 points | Greater reduction in modified Ashworth spasticity score with cannabis |
| 5.28 points | Greater pain reduction on visual analogue scale with cannabis (P = 0.008) |
| -8.67 points | Cognitive performance DECREASED more with cannabis (P = 0.003) |
Highly significant reduction in spasticity with smoked cannabis vs placebo
Greater reduction in modified Ashworth spasticity score with cannabis
Greater pain reduction on visual analogue scale with cannabis (P = 0.008)
Cognitive performance DECREASED more with cannabis (P = 0.003)
What This Means for Spasticity Patients
If you have MS with treatment-resistant spasticity, this trial provides evidence that smoked cannabis can help with muscle stiffness and pain.
Smoked cannabis significantly reduced spasticity (P < 0.0001) and pain (P = 0.008) compared to placebo.
However, there is a trade-off: cannabis also significantly impaired cognitive function (P = 0.003). Walking speed was not affected.
No serious adverse events occurred, suggesting short-term use is relatively safe.
The researchers suggest that future studies should explore different doses that might provide the benefits with "less cognitive impact." For patients whose spasticity does not respond to other treatments, the benefits may outweigh the cognitive effects, but this is an individual decision to make with your neurologist.
Quick Answers: Spasticity and Cannabis
Direct answers based on the findings of this study:
Research Summary: Answers are based on published peer-reviewed studies and represent research findings, not medical recommendations. Individual results may vary. Always consult a healthcare provider before making treatment decisions.
Does marijuana help MS muscle stiffness?
Yes. A 2012 RCT found smoked cannabis significantly reduced MS spasticity by 2.74 points more than placebo (P < 0.0001) and pain by 5.28 points (P = 0.008). However, cognitive function was significantly impaired (P = 0.003).
Source: Corey-Bloom et al., CMAJ, 2012 (PMID: 22586334)
Does cannabis affect thinking in MS patients?
Yes. In this RCT, cognitive function (PASAT score) decreased by 8.67 points more with cannabis than placebo (P = 0.003). The researchers recommended future studies explore doses that provide benefit "with less cognitive impact."
Source: Corey-Bloom et al., CMAJ, 2012 (PMID: 22586334)
Does cannabis help MS pain and spasticity?
Yes for both. A 37-patient RCT found smoked cannabis significantly reduced spasticity (P < 0.0001) and pain (P = 0.008) vs placebo. However, there is a trade-off: cognitive function was also significantly impaired (P = 0.003).
Source: Corey-Bloom et al., CMAJ, 2012 (PMID: 22586334)
This is educational content, not medical advice
The research summarized here is for informational purposes only. Individual results may vary, and what works in studies may not work the same way for everyone. Always consult with a qualified healthcare provider before making changes to your treatment plan or starting medical cannabis therapy.
Important Limitations
This study has some caveats to keep in mind when interpreting the results:
- Small sample size (30 completers)
- Short duration (3 days per treatment period)
- Crossover design may have carryover effects
- Significant cognitive impairment with cannabis
- Cannot determine optimal dose for benefit without cognitive harm
The Bottom Line on Cannabis for Spasticity
This RCT found smoked cannabis significantly reduces MS spasticity (P < 0.0001) and pain (P = 0.008) compared to placebo. However, cognitive function was significantly impaired (P = 0.003). No serious adverse events occurred. For treatment-resistant MS spasticity, cannabis may help with symptoms but the cognitive trade-off should be considered. Future research should explore doses that provide benefit with less cognitive impact.
Do You Qualify for Medical Marijuana?
If you're living with Spasticity, you may qualify for a medical marijuana card. Our licensed physicians can evaluate you from home via telehealth.
Related Research & Resources
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- What Does Science Actually Know About Medical Cannabis?
- Cannabis Benefits and Risks: What 101 Studies Reveal
- Cannabis for Chronic Pain: A Critical Look at 104 Studies
- Clinical Practice Guidelines: Cannabis for Chronic Pain & Co-Occurring Conditions (2024)
- Cannabis for Pain: A Complete Overview of the Evidence
Condition Research
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This condition qualifies for medical marijuana in:
Source
Corey-Bloom J, Wolfson T, Gamst A, et al. "Smoked cannabis for spasticity in multiple sclerosis: a randomized, placebo-controlled trial" CMAJ. 2012.
Important Information
Study Age: This study was published 14 years ago. Newer research may have updated or refined these findings.
Not Medical Advice: This research summary is for educational purposes only. It should not be used to diagnose, treat, cure, or prevent any disease or medical condition. Always consult a qualified healthcare provider before starting or changing any treatment.
Individual Variation: Research findings represent group averages. Your individual response to cannabis may differ based on genetics, other medications, underlying conditions, and many other factors.
Last reviewed: January 25, 2026
Important Notices
Research Summary Disclaimer
This content represents our interpretation of published scientific research for educational purposes. It should not be used to make treatment decisions without consulting a qualified healthcare provider. Individual results may vary from study findings.
FDA Notice
These statements have not been evaluated by the FDA. Cannabis is not intended to diagnose, treat, cure, or prevent any disease. The FDA has not approved cannabis for any medical condition except specific prescription medications.
Copyright & Fair Use
Research summaries are provided under fair use (17 U.S.C. § 107) for educational purposes. We provide brief summaries with attribution, not full reproductions. All studies remain the intellectual property of their respective authors and publishers.
Data Sources
Study information sourced from PubMed®, U.S. National Library of Medicine. Inclusion does not imply endorsement by NLM, NIH, or the federal government.
For complete information, see our Terms of Use and Research Content Policy.
FAQs: Cannabis for Spasticity
Does smoking cannabis help MS spasticity?
Yes. This RCT found smoked cannabis significantly reduced spasticity (P < 0.0001) and pain (P = 0.008) compared to placebo. However, cognitive function was also significantly impaired (P = 0.003). No serious adverse events occurred.
What are the side effects of cannabis for MS?
Cognitive impairment is the main concern. Cognitive function (PASAT) decreased by 8.67 points more with cannabis than placebo (P = 0.003). No serious adverse events occurred during the 3-day treatment periods.
Is smoked cannabis better than other forms for MS?
Smoked cannabis, with benefit-risk tradeoff. Significant benefits for spasticity and pain were found, but also cognitive impairment. Researchers suggested exploring different doses or forms for "similar beneficial effects with less cognitive impact."