Coming off cannabis: a cognitive and magnetic resonance imaging study in patients with multiple sclerosis
Anthony Feinstein, Cecilia Meza, Cristiana Stefan, Richard W. Staines
Brain July 3, 2019 DOI: 10.1093/brain/awz213 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Quasi-experimental study with odd-even allocation Peer reviewed |
|---|---|
| Sample size | 40 |
| Population | Patients with multiple sclerosis who began using cannabis after disease onset, used it at least 4 days per week for many years, and were globally cognitively impaired at baseline |
| Duration | 28 days |
| Measures | Brief Repeatable Neuropsychological Battery for multiple sclerosis, Symbol Digit Modalities Test, structural MRI, functional MRI, urine cannabinoid metabolites |
| Topics | Cannabis |
| Citations | 32 |
| Key findings | After 28 days, patients with multiple sclerosis who abstained from long-term frequent cannabis use performed significantly better on every cognitive index than those who continued using cannabis (P < 0.0001 for all), and showed faster reaction time and more correct trials on a functional MRI task with increased activation in task-related brain regions. The authors state that these improvements are not solely attributable to practice effects. |
Abstract
Cognitive dysfunction affects 40-80% of patients with multiple sclerosis. Smoking cannabis may add to these deficits. It is unclear whether coming off cannabis results in cognitive improvement. To address this question, 40 patients with multiple sclerosis who started using cannabis after the onset of multiple sclerosis and who used it for at least 4 days a week over many years were divided by odd-even number selection into two groups: cannabis continuation and cannabis withdrawal. Assessments took place at baseline and after 28 days and included serial versions of the Brief Repeatable Neuropsychological Battery for multiple sclerosis containing tests of verbal and visual memory, processing speed and executive function; structural and functional MRI, the latter entailing a compatible version of the Symbol Digit Modalities Test; urine for cannabinoid metabolites to detect compliance with abstinence. Only those participants deemed globally impaired at baseline (failure on at least two cognitive domains) were enrolled. The results revealed that the two groups were well matched demographically and neurologically. One subject was removed from the withdrawal group because of failed abstinence. Urine analysis revealed the cannabinoid consumed was predominantly tetrahydrocannabinol (THC). There were no baseline between group cognitive differences, but by Day 28 the withdrawal group performed significantly better on every cognitive index (P < 0.0001 for all). Significant within group differences were present for every test over time, but only in the abstinent group (P < 0.0001 for all tests). There were no between group baseline or Day 28 differences in structural MRI indices (global atrophy, total T1 and T2 lesion volume). At index assessment the two groups had a similar performance on the functional MRI-compatible Symbol Digit Modalities Test and there were no group differences in brain activation. However, by Day 28, the withdrawal group completed more trials correctly (P < 0.012) and had a faster reaction time (P < 0.002), associated with significantly increased activation in brain regions known to be associated with performance of the test (bilateral inferior frontal gyri, caudate and declive/cerebellum, P < 0.001 for all regions). These results reveal that patients with multiple sclerosis who are frequent, long-term cannabis users can show significant improvements in memory, processing speed and executive function after 28 days of drug abstinence. The absence of similar improvements in a matched multiple sclerosis group that remained on cannabis shows that beneficial cognitive change after stopping cannabis is not solely attributable to the effects of practice.
Comparable studies
Other experimental studies on cannabis, most cited first.