Stopping Cannabis Aids Cognition in MS, But Not Awareness of Gains

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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Cannabis and MS

Cannabis use

People with multiple sclerosis (MS) may not be entirely aware of the decline in their cognitive abilities with cannabis use, which may explain why many choose to continue with it, a small study in patients who are long-term cannabis users reported.

The study, “Impaired awareness: Why people with multiple sclerosis continue using cannabis despite evidence to the contrary,” was published in the journal Brain and Behavior by a team of researchers in Canada.

Broader moves toward legalization of cannabis, also known as marijuana, have resulted in rising numbers of users.

“This general enthusiasm for the drug cannot, however, explain its standout acceptance among people with multiple sclerosis,” the researchers wrote. In a recent survey, two-thirds of people with MS were found to be current cannabis users.

MS patients use cannabis for a variety of reasons, “the most frequent being managing pain, spasticity, depression, anxiety, insomnia, and fatigue,” the researchers wrote.

But evidence indicates that cannabis may also cause harm. Previous work by this research team found depression significantly eased and cognitive abilities — memory, processing speed, and executive function — improved in MS patient groups who stopped using the drug for 28 days.

These researchers now aimed to understand why people with MS continued using cannabis despite its known cognitive risks. Their hypothesis was that these patients, due to their disease, have a lesser awareness and understanding of their thoughts (a process known as metacognition), which could explain — at least partly — their predisposition to cannabis use.

The study enrolled 40 cognitively impaired adults with MS who were “longstanding, frequent” cannabis users. Of them, 20 were taken off the drug (one left the study due to cannabis use), while the other 20 continued using it. Both groups were again followed for 28 days, or about one month.

Patients’ cognitive skills were tested before and after the intervention using a 30-minute battery of cognitive testing focusing on information processing speed, working memory, learning, and attention. It is called the Brief Repeatable Battery of Neuropsychological Tests (BRB-N).

People in the withdrawal group improved significantly “across multiple domains such as processing speed, learning, verbal and visual memory, and executive function” after being off cannabis for 28 days, the researchers reported.

In contrast, those who continued using cannabis showed no changes in cognitive function between the study’s start and testing given 28 days later.

“Most notably, cognitive improvement was not accompanied by a self-awareness of this positive cognitive change,” the researchers wrote, adding that all 19 withdrawal group patients returned to regular cannabis use for reasons similar to those initially given.

Patients using cannabis to manage depression also showed a reduction in their depression scores (indicating lesser depression) after stopping cannabis for 28 days, while those who continued taking it had no changes in these scores.

As depression negatively impacts mood and self-awareness of cognition, the researchers controlled for this factor when investigating self-awareness, physical abilities, and psychosocial functioning. Other factors that were also taken into account were disease duration and cannabis levels in the blood.

Researchers also found that withdrawal group patients were less likely to do things away from home during that time. This “negative change … gives a possible clue as to why all our study participants returned to using cannabis after a month of abstinence. The ‘reward’ that comes with this recidivism is a less constrictive lifestyle, which in the context of a disabling illness like MS, cannot be underestimated,” they wrote.

They also attributed this change in habit to a deficit in metacognition, which they described as relying on executive functions and self-awareness.

“When people with MS who have been using cannabis on a daily basis over many years discontinue the drug and remain abstinent for at least 28 days, significant cognitive improvement occurs across multiple domains such as processing speed, learning, verbal and visual memory, and executive function,” the researchers wrote.

However, patients do not appear to be aware of this improvement. “In short, there is a failure of self-awareness … thereby compromising metacognition and leading to decisions related to persistent cannabis use that are self-injurious,” the researchers wrote.

Approaches that aim to improve metacognition may be of help here, they added.

“This potentially opens the door to assisting people with MS gain more awareness of how cannabis … can harm their cognition. If successfully applied, such an approach has the potential to better inform an individual’s decision when it comes to weighing the pros and cons of using the drug,” the researchers concluded.