Cannabis May Impair Cognition in Multiple Sclerosis

Controversial drug may cause more harm than good

THURSDAY, Feb. 14 (HealthDay News) -- While some have advocated the use of cannabis in the treatment of multiple sclerosis, a new study reports that patients with multiple sclerosis (MS) who smoke marijuana have more cognitive abnormalities and are more likely to meet criteria for psychiatric disorders than non-users, according to an article published online Feb. 13 in Neurology.

Omar Ghaffar, M.D., of the University of Toronto in Canada, and a colleague assessed a sample of 140 MS patients from an outpatient clinic for the presence of psychiatric disorders and cannabis use, and then tested their cognition, processing speed, memory, and attention using the Neuropsychological Battery for MS and the Symbol Digit Modalities Test.

The investigators found that 10 subjects (7.7 percent) were current cannabis users. When the researchers compared each cannabis user to four matched subjects with MS who were not using cannabis, they found that a higher proportion of cannabis users met DSM-IV criteria for a psychiatric diagnosis than non-users. In addition, cannabis users had slower mean performance time and different response patterns in tests of cognition compared to matched controls.

"In the absence of previously published research, our data provide the first evidence of the injurious effect of inhaled cannabis on the mentation of patients with MS," the authors write.

One author reports receiving honoraria from several pharmaceutical companies.

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