STOCKHOLM – The good news about cognitive impairment in patients with multiple sclerosis who’ve been using cannabis heavily for symptom relief – even for many years – is that their memory, executive function, and information processing speed will improve significantly once they’ve been off the drug for just 28 days, according to the results of a randomized trial presented at the annual congress of the European Committee for Treatment and Research in Multiple Sclerosis.
“It’s good for neurologists to know that, if they prescribe cannabis or their patient is self-medicating and chooses to stop, their cognition will improve considerably,” observed Cecilia Meza, a coinvestigator in the study led by, professor of psychiatry at the University of Toronto.
But there’s a surprise twist to this study, she explained in an interview: “We showed patients their results, and they also felt that their cognition was doing a lot better, but despite that, they would rather be using cannabis to feel better than to have their memory intact. The pain was that bad,” said Ms. Meza, a research coordinator at the university’s Sunnybrook Research Institute.
It’s known that cognitive impairment in healthy long-term cannabis users, provided they started as adults, is fully reversed after 28 days of abstinence. But disease-related cognitive dysfunction affects 40%-80% of patients with MS, and cannabis use may compound this impairment.
The study included 40 MS patients with global impairment of cognition, none of whom were cannabis users prior to their diagnosis. They typically started using it for MS symptom relief 2-3 years after receiving their diagnosis. By the time they were approached for study participation, they had been using cannabis four to five times per day or more for an average of 7 years for relief of symptoms, including incontinence, spasticity, poor sleep, headaches, and difficulties in eating.
All participants were willing to try 28 days of abstinence; half were randomized to do so, while the others stayed the course. Study endpoints included change from baseline to day 28 in the Brief Repeatable Neuropsychological Battery, functional MRI done while taking the Symbol Digit Modalities Test, and urine testing to assure compliance with abstinence.
By day 28, the abstinence group – and with one exception, urine testing confirmed they were bona fide cannabis quitters for the study duration – performed significantly better on the neuropsychological test battery than at baseline, with an associated significant increase in brain activation in the bilateral inferior frontal gyri, as well as the caudate and declive cerebellum while executing the Symbol Digit Modalities Test. The control group who kept on using cannabis showed no such improvements.
The full study details were published in conjunction with Ms. Meza’s presentation ().
She reported having no financial conflicts regarding the study, funded by the Multiple Sclerosis Society of Canada.
SOURCE: Meza C. ECTRIMS 2019, .