MS patients who used cannabis performed worse on cognitive tests and were twice as likely to be cognitively impaired
Among 50 MS patients, cannabis users performed significantly worse on processing speed, working memory, executive function, and visuospatial perception, and were twice as likely to be globally cognitively impaired.
Quick Facts
What This Study Found
Researchers compared 25 MS patients who used cannabis to 25 matched MS non-users using a comprehensive neuropsychological battery designed specifically for MS.
Cannabis users performed significantly worse on information processing speed, working memory, executive functions, and visuospatial perception. They were twice as likely to be classified as globally cognitively impaired.
Importantly, there were no differences in depression, anxiety, or lifetime psychiatric diagnoses between the groups, meaning the cognitive differences were not explained by mood disorders.
The authors noted that whatever subjective benefits patients derived from cannabis (pain or spasticity relief) should be weighed against these cognitive costs, particularly since MS already causes cognitive deterioration.
Key Numbers
25 cannabis users vs 25 non-users. Cannabis users twice as likely to be globally cognitively impaired. Significantly worse on processing speed, working memory, executive function, and visuospatial perception. No mood differences between groups.
How They Did This
Cross-sectional study of 50 MS patients (25 cannabis users, 25 non-users). Minimal Assessment of Cognitive Function in MS battery, Hospital Anxiety and Depression Scale, and SCID-I administered. Group-matching and regression controlled for age, sex, education, premorbid intelligence, disability, and disease characteristics.
Why This Research Matters
Since MS already impairs cognition, the finding that cannabis compounded these deficits was clinically significant for the many MS patients using cannabis for symptom relief.
The Bigger Picture
This study raised important questions about the risk-benefit balance of cannabis use in MS, where symptom relief must be weighed against potential cognitive harm in a population already vulnerable to cognitive decline.
What This Study Doesn't Tell Us
Cross-sectional design cannot determine whether cannabis caused the cognitive deficits or whether more cognitively impaired patients were drawn to cannabis use. "Street cannabis" was used, not standardized pharmaceutical products. Small sample size.
Questions This Raises
- ?Would pharmaceutical cannabis products (like Sativex) produce the same cognitive effects?
- ?Do the cognitive costs outweigh the symptom benefits for individual patients?
Trust & Context
- Key Stat:
- 2x more likely to be globally cognitively impaired among cannabis-using MS patients
- Evidence Grade:
- Well-matched cross-sectional study with comprehensive neuropsychological battery but small sample size and inability to establish causation.
- Study Age:
- Published in 2011. Research on cannabis and MS cognition has continued to develop.
- Original Title:
- Effects of cannabis on cognitive function in patients with multiple sclerosis.
- Published In:
- Neurology, 76(13), 1153-60 (2011)
- Authors:
- Honarmand, Kimia, Tierney, Mary C, O'Connor, Paul(2), Feinstein, Anthony
- Database ID:
- RTHC-00490
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis worsen thinking problems in MS?
In this study, MS patients who used cannabis performed significantly worse on cognitive tests. However, the study could not determine whether cannabis caused the impairment or whether patients with worse cognition were more likely to use cannabis.
Should MS patients avoid cannabis?
This study suggested that cannabis users with MS had worse cognitive outcomes. The authors recommended weighing subjective benefits (pain, spasticity relief) against potential cognitive costs, particularly since MS already affects cognition.
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Cite This Study
https://rethinkthc.com/research/RTHC-00490APA
Honarmand, Kimia; Tierney, Mary C; O'Connor, Paul; Feinstein, Anthony. (2011). Effects of cannabis on cognitive function in patients with multiple sclerosis.. Neurology, 76(13), 1153-60. https://doi.org/10.1212/WNL.0b013e318212ab0c
MLA
Honarmand, Kimia, et al. "Effects of cannabis on cognitive function in patients with multiple sclerosis.." Neurology, 2011. https://doi.org/10.1212/WNL.0b013e318212ab0c
RethinkTHC
RethinkTHC Research Database. "Effects of cannabis on cognitive function in patients with m..." RTHC-00490. Retrieved from https://rethinkthc.com/research/honarmand-2011-effects-of-cannabis-on
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.