Marijuana may have negative effects

THE QUESTION People with multiple sclerosis sometimes turn to marijuana for relief from the pain, spasticity, insomnia, bladder problems, tremors and emotional distress that can accompany the disease. Might its use have less desirable effects?

THIS STUDY involved 50 adults with MS whose average age was 44. Half regularly used street marijuana for medicinal and/or recreational purposes and had done so, on average, for 27 years. They used no other illicit drugs. The other participants — of comparable age, sex, education level, IQ and disease status — had not used marijuana. Results from a battery of standardized neuropsychological tests showed that the marijuana users had greater deficits in such areas as memory, executive functioning (the ability to plan, organize and attend to details) and visuospatial perception. Scores for information-processing speed, for example, were a third lower for marijuana users than for the others. Overall, almost half of the participants were deemed cognitively impaired: 16 of the marijuana users and eight of the nonusers.

WHO MAY BE AFFECTED? Adults with MS, a disease of the central nervous system that disrupts, to varying degrees, communication between the brain and other parts of the body. In severe cases, it can rob people of the ability to speak, write or walk. MS affects women far more often than men.

CAVEATS The study size was small. The findings might not apply to people with MS who use marijuana infrequently or for a short time, or to those who obtain it from a legal marijuana pharmacy. Whether thinking skills would improve after a long time without marijuana use was not tested.

FIND THIS STUDY March 29 issue of Neurology

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— Linda Searing

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.