MONDAY, March 28 (HealthDay News) -- As the debate over medical marijuana use continues, a new study among multiple sclerosis patients -- who often use the drug to relieve pain and muscle spasticity -- adds to the argument that smoking pot clouds thinking skills.
Canadian researchers studied two groups of 25 people between the ages of 18 and 65 with MS, an autoimmune disease that attacks the central nervous system and can lead to paralysis, cognitive problems, incontinence and a host of other sensory and functional deficits. One group used marijuana heavily, while the other group reported no marijuana use for many years.
Patients using pot performed significantly worse on cognitive tests measuring attention, thinking speed, executive function and visual perception of spatial relationships between objects, the study authors said. Users were also twice as likely to be classified as globally cognitively impaired, meaning they failed at least two of 11 various assessments.
The study is published in the March 29 issue of Neurology.
"We published a paper a few years back that said cannabis use in MS patients might be linked to delays in processing speed, but it was a very small sample," said study author Dr. Anthony Feinstein, a professor of psychiatry at the University of Toronto. "This confirms our earlier impressions that cannabis could, in fact, have some cognitive side effects . . . but I'm surprised at the breadth. We were thinking we would probably replicate our earlier findings, but it went beyond that."
Data suggests that between 36 percent and 43 percent of MS patients have smoked pot at some time, according to the study, and "a substantial minority" find cannabis relieves pain, insomnia, spasticity, tremors, bladder problems and emotional distress.
Between 40 percent and 60 percent of MS patients are cognitively impaired to begin with, Feinstei
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