Cannabis Users with MS Show Poorer Processing Speed and Working Memory
Among 847 people with MS, cannabis users performed significantly worse on processing speed and working memory tests, even after controlling for age, education, disease duration, anxiety, and fatigue.
Quick Facts
What This Study Found
Cannabis users (n = 254) performed significantly worse than nonusers (n = 593) on the Symbol Digit Modalities Test (processing speed, p = 0.014). After adjustment, cannabis independently predicted poorer performance on SDMT, PASAT-3, and PASAT-2 (all p < 0.001), explaining 7-16% of variance.
Key Numbers
847 patients; 254 cannabis users (30%); significant effects on SDMT (p = 0.014); SDMT, PASAT-3, PASAT-2 all p < 0.001 after adjustment; models explained 7-16% of variance.
How They Did This
Cross-sectional study of 847 consecutive MS patients administered the MACFIMS cognitive battery. Cannabis users (n = 254) compared to nonusers (n = 593) using MANOVA and multiple linear regression controlling for age, education, disease duration, anxiety, and fatigue.
Why This Research Matters
People with MS already face cognitive challenges, particularly with processing speed. If cannabis use compounds these deficits, it is relevant information for patients using cannabis for symptom relief who may not realize the cognitive trade-off.
The Bigger Picture
Cannabis is commonly used by MS patients for pain, spasticity, and sleep. This is the largest study to examine objective cognitive effects in this population. As cannabis potency increases and legalization expands, the cognitive impact in vulnerable neurological populations warrants attention.
What This Study Doesn't Tell Us
Cross-sectional design cannot determine whether cannabis caused cognitive deficits or whether those with worse cognition are more likely to use cannabis. No information on cannabis type, potency, frequency, or mode of use. Recreational users only.
Questions This Raises
- ?Does the cognitive impact differ by cannabis potency or consumption method in MS patients?
- ?Would longitudinal data show that cannabis use accelerates cognitive decline in MS?
Trust & Context
- Key Stat:
- 30% of MS patients used cannabis; all showed poorer processing speed
- Evidence Grade:
- Large consecutive clinical sample with validated cognitive battery and adjusted analyses, but cross-sectional design limits causal inference.
- Study Age:
- 2025 publication
- Original Title:
- Cannabis and Cognitive Function in Multiple Sclerosis: Findings From a Large Consecutive Clinical Sample.
- Published In:
- European journal of neurology, 32(7), e70142 (2025)
- Authors:
- Kever, Anne, Meza, Cecilia(3), Feinstein, Anthony(8)
- Database ID:
- RTHC-06814
Evidence Hierarchy
Frequently Asked Questions
Does cannabis affect thinking in people with MS?
In this study of 847 MS patients, cannabis users scored significantly lower on tests of processing speed and working memory compared to nonusers, even after accounting for age, education, disease duration, anxiety, and fatigue.
Should people with MS avoid cannabis?
This study found an association between cannabis use and poorer cognitive performance in MS, but it cannot prove cannabis caused the deficits. MS patients using cannabis for symptom relief should be aware of potential cognitive trade-offs and discuss them with their neurologist.
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Cite This Study
https://rethinkthc.com/research/RTHC-06814APA
Kever, Anne; Meza, Cecilia; Feinstein, Anthony. (2025). Cannabis and Cognitive Function in Multiple Sclerosis: Findings From a Large Consecutive Clinical Sample.. European journal of neurology, 32(7), e70142. https://doi.org/10.1111/ene.70142
MLA
Kever, Anne, et al. "Cannabis and Cognitive Function in Multiple Sclerosis: Findings From a Large Consecutive Clinical Sample.." European journal of neurology, 2025. https://doi.org/10.1111/ene.70142
RethinkTHC
RethinkTHC Research Database. "Cannabis and Cognitive Function in Multiple Sclerosis: Findi..." RTHC-06814. Retrieved from https://rethinkthc.com/research/kever-2025-cannabis-and-cognitive-function
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.