Four weeks without cannabis reversed brain network changes and improved cognition in people with MS | Research

The takeaway

After 28 days of cannabis abstinence, people with MS showed restored default mode network activity in key brain regions and significant cognitive improvements across multiple domains.

MS patients using cannabis, neurologists, neuropsychologists, and researchers studying cannabis effects on brain networks.

What the researchers found

The cannabis withdrawal group showed increased activation at day 28 in the left posterior cingulate, right angular gyrus, left hippocampus, and right medial prefrontal cortex compared to baseline. The cannabis continuation group showed no changes. Cognitive improvements accompanied the brain changes in the withdrawal group.

Why it matters

This study provides direct neuroimaging evidence that cannabis-related cognitive impairment in MS is reversible. The default mode network changes map onto the specific brain regions responsible for the cognitive improvements observed.

The numbers in context

33 participants (15 continuation, 18 withdrawal). Key regions with increased activation after abstinence: left posterior cingulate, right angular gyrus, left hippocampus (BA 36), right medial prefrontal cortex. All p<0.05 TFCE corrected. Multiple cognitive domain improvements in withdrawal group.

How the study worked

Prospective study of 33 cognitively impaired people with MS who were frequent cannabis users, assigned to cannabis continuation (n=15) or withdrawal (n=18) groups. Neuropsychological assessments and resting-state fMRI at baseline and day 28, with urine monitoring for compliance.

What this study cannot tell us

Small sample without randomization (assignment, not random allocation, to groups). 28-day follow-up may not capture full recovery trajectory. Cannot separate cannabis withdrawal effects from direct recovery of suppressed brain function.

How to read the evidence

Prospective design with neuroimaging and compliance monitoring provides strong mechanistic evidence, though small sample and non-randomized group assignment limit certainty.

When this study was published

2024 publication.

The bigger picture

People with MS already face cognitive challenges from the disease itself. This study shows that frequent cannabis use adds a reversible layer of cognitive impairment, and that even long-term users can see meaningful recovery in just four weeks.

Questions still open

Would longer abstinence produce additional cognitive and brain network recovery?
Can MS patients who use cannabis for symptom management find a usage pattern that minimizes cognitive impact?

Common questions

What is the default mode network?

A network of brain regions active during rest and internal thought, including the posterior cingulate, angular gyrus, hippocampus, and medial prefrontal cortex. It plays a central role in memory, self-reflection, and cognitive processing.

Does this mean cannabis is bad for people with MS?

The study shows frequent cannabis use suppresses brain network function in MS patients, but this effect reverses with abstinence. For patients using cannabis to manage symptoms like spasticity or pain, the findings suggest balancing symptom relief against cognitive costs.

Read the original research

The effects of cannabis abstinence on cognition and resting state network activity in people with multiple sclerosis: A preliminary study.

NeuroImage. Clinical, 43, 103622

View on PubMed ↗Publisher’s paper ↗

Citation

Meza, Cecilia; Stefan, Cristiana; Staines, W Richard; Feinstein, Anthony. (2024). The effects of cannabis abstinence on cognition and resting state network activity in people with multiple sclerosis: A preliminary study.. NeuroImage. Clinical, 43, 103622. https://doi.org/10.1016/j.nicl.2024.103622