Neurology Reviews - July 2014

Patients with multiple sclerosis (MS) who smoke marijuana regularly have more cognitive deficits than patients with MS who do not smoke marijuana, according to research published May 27 in Neurology. Marijuana use may be associated with impairments in information processing speed, visual memory, and working memory among these individuals.

In a cross-sectional study, cannabis users had more diffuse cerebral activation during a test of working memory, compared with nonusers. The cannabis users also had increased activation in parietal and anterior cingulate brain regions implicated in working memory, relative to nonusers.

But investigators found no differences in brain
structure between the study groups, and this find-
ing is consistent with the results of cannabis imaging
studies in healthy subjects.

Subjects Underwent Imaging and Neuropsychologic Tests

Bennis Pavisian, research assistant at Sunnybrook Hospital in Toronto, and colleagues recruited 39 patients (ages 18 to 60) with a confirmed diagnosis of MS for their study. They enrolled 20 participants who regularly used cannabis and whose urine tested positive for cannabis metabolites. The investigators asked participants not to use cannabis for 12 hours before the trial. Nineteen patients with MS who had never used cannabis were matched to the other participants using demographic and disease-related variables.