Marijuana may hasten mental decline in MS: study
Last Updated: 2011-03-28 19:41:20 -0400 (Reuters Health)
By Frederik Joelving
NEW YORK (Reuters Health) - Although medical marijuana has been legalized in many U.S. states, people with multiple sclerosis should think twice before they start using the drug routinely, researchers say.
In a small study published online today in Neurology, they found people with MS did worse on a number of psychological tests if they were heavy marijuana smokers.
"In multiple sclerosis, you already have a group of patients who are cognitively impaired," said Dr. Anthony Feinstein, a psychiatrist at the University of Toronto who led the new work. "When you add marijuana to the mix, you might worsen those problems."
Still, the study doesn't prove that marijuana fuels mental decline, Dr. Feinstein said. And even if it does, some people might choose to live with that trade-off.
Many people with chronic diseases say the illegal drug helps relieve their symptoms, and a few studies have hinted that cannabis extracts might alleviate pain, spasticity and other problems in MS.
According to the National MS Society, some 400,000 Americans have MS. Of those, about one in six smoke marijuana, Dr. Feinstein said, yet almost no research has looked at how it affects their minds.
"There are just no data on the topic," Dr. Feinstein told Reuters Health.
So he and his colleagues decided to compare the mental skills of two groups of 25 people with MS. One group was made up of regular marijuana users -- the majority had smoked it daily for many years -- and the other included only non-users.
The two groups were matched on age, stage and course of disease, education and other factors.
Nearly two-thirds of the marijuana smokers were classified as cognitively impaired based on a several psychological tests, such as information processing speed and verbal memory (all taken at least 12 hours after the patients had last used marijuana).
By comparison, only a third of the non-users had similar mental impairment.
The effect was independent of other factors that might affect mental functioning - such as whether the participants drank alcohol or were depressed or anxious.
Still, short of running a randomized controlled trial, it's impossible to prove that marijuana use caused the lower mental performance seen in the regular pot smokers.
"It's not really surprising," said Dr. Shaheen Lakhan of the Cleveland Clinic in Ohio, who also runs the non-profit Global Neuroscience Initiative Foundation in Panorama City, California.
"It's a long established observation that there are negative cognitive effects on cannabis users," Dr. Lakhan said. "But I must say that most MS patients that I am familiar with find that their pain and spasticity are very disturbing, and they might choose this as a priority."
He added that all the medications approved to treat MS symptoms, including muscle relaxants, have side effects.
Dr. Feinstein said people with MS should be careful about smoking marijuana, especially because the therapeutic benefits appear to be weak.
Still, he said, people in different situations may have different priorities.
"I don't want to be dogmatic about it," Dr. Feinstein told Reuters Health. "It's really going to vary with the individual patient."
SOURCE:http://bit.ly/flYIgI
Neurology 2011.
© 2010 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.
