MS Patients Who Smoke Cannabis Show More Widespread Brain Volume Loss and Cognitive Impairment | Research

The takeaway

Multiple sclerosis patients who smoked cannabis for symptom relief had more extensive cognitive deficits and greater brain volume loss in key regions compared to matched MS patients who did not use cannabis.

Read this if you have MS and use cannabis for symptom relief.

Same brain volume loss = more cognitive impairment in cannabis-using MS patients

What the researchers found

Researchers compared 20 MS patients who smoked cannabis for symptom relief with 19 matched MS patients who did not. Both groups received cognitive testing and structural MRI brain scans.

Both groups showed correlations between reduced brain volume and cognitive impairment, but the cannabis group had more extensive deficits. Gray matter volume loss in the thalamus, basal ganglia, medial temporal, and medial prefrontal regions, plus white matter loss in the fornix, correlated with cognitive problems.

Critically, the same amount of brain volume reduction was associated with more widespread cognitive impairment in cannabis users than non-users, suggesting cannabis amplifies the cognitive impact of MS-related brain damage.

Why it matters

Many MS patients use cannabis for symptom relief, but this study suggests it may worsen the cognitive decline that is already a major burden of the disease. The finding that cannabis amplifies the cognitive impact of brain atrophy is particularly concerning.

The numbers in context

20 cannabis-using vs. 19 non-using MS patients; gray matter analysis: 33% variance, p<0.0001; white matter analysis: 17% variance, p<0.05; affected regions: thalamus, basal ganglia, medial temporal, prefrontal, fornix

How the study worked

Cross-sectional study comparing 20 cannabis-using and 19 non-using MS patients matched on demographics. Structural MRI with Partial Least Squares multivariate analysis of brain-behavior associations. Cognitive assessment with the Brief Repeatable Neuropsychological Battery.

What this study cannot tell us

Small sample sizes. Cross-sectional design cannot determine causation. Cannabis users may have had more severe MS leading to both more cannabis use and more cognitive decline. Did not control for cannabis dose or frequency.

How to read the evidence

Well-designed neuroimaging study with matched groups, but small sample and cross-sectional design limit causal conclusions.

When this study was published

Published in 2015. Research on cannabis effects in MS continues, with growing interest in CBD-only formulations.

The bigger picture

MS patients face a difficult trade-off: cannabis may help with spasticity and pain but could accelerate cognitive decline. Understanding this trade-off is essential for informed treatment decisions.

Questions still open

Would non-smoked cannabis products show the same cognitive impact? Is the additional cognitive impairment reversible if cannabis use stops? Could CBD without THC provide symptom relief without the cognitive cost?

Common questions

Does cannabis make MS cognitive problems worse?

This study found that MS patients who used cannabis had more widespread cognitive deficits relative to their brain volume loss than non-users. This suggests cannabis may amplify the cognitive impact of MS-related brain damage, though the cross-sectional design cannot prove causation.

Should MS patients stop using cannabis?

This study raises concerns about cognitive effects but does not provide a simple answer. Cannabis may help with spasticity and pain. Patients should discuss the potential cognitive trade-offs with their neurologists.

Read the original research

Multiple sclerosis, cannabis, and cognition: A structural MRI study.

NeuroImage. Clinical, 8, 140-7

View on PubMed ↗Publisher’s paper ↗

Citation

Romero, Kristoffer; Pavisian, Bennis; Staines, William R; Feinstein, Anthony. (2015). Multiple sclerosis, cannabis, and cognition: A structural MRI study.. NeuroImage. Clinical, 8, 140-7. https://doi.org/10.1016/j.nicl.2015.04.006