Public Release: 

Smoked cannabis can help relieve muscle tightness and pain in people with multiple sclerosis

Benefits come with negative cognitive effects

Canadian Medical Association Journal

People with multiple sclerosis may find that smoked cannabis provides relief from muscle tightness -- spasticity -- and pain, although the benefits come with adverse cognitive effects, according to a new study published in CMAJ (Canadian Medical Association Journal).

Many patients with multiple sclerosis suffer from spasticity, an uncomfortable and disabling condition in which the muscles become tight and difficult to control. While there are drugs to relieve spasticity, they can have adverse effects and do not always sufficiently improve the condition in some patients.

Researchers from the University of California, San Diego School of Medicine, conducted a randomized, double-blinded controlled trial with 30 participants to understand whether smoked cannabis can have an effect on muscle spasticity in people whose spasticity does not respond well to existing treatment. The average age of participants was 50 years, and 63% were female. More than half of the participants needed walking aids, and 20% used wheelchairs.

Most trials have focused on the effect of oral cannabis rather than smoked cannabis.

Rather than rely on self-reporting by patients regarding their muscle spasticity -- a subjective measure -- health professionals rated the spasticity of each participant's joints on the modified Ashworth scale, a common objective tool to evaluate intensity of muscle tone. The researchers found that participants in the smoked cannabis group experienced an almost one-third decrease on the Ashworth scale -- 2.74 points -- from a baseline score of 9.3, meaning spasticity improved, compared with the placebo group. As well, pain scores decreased by about 50%.

"We saw a beneficial effect of smoked cannabis on treatment-resistant spasticity and pain associated with multiple sclerosis among our participants," writes Dr. Jody Corey-Bloom, Department of Neuroscience, University of California, San Diego, California, with coauthors. "Although generally well-tolerated by our participants, smoking cannabis was accompanied by acute cognitive effects."

Cognitive function was negatively affected in the smoked cannabis group but not with placebo, as measured by the ability to perform an addition test requiring focused attention. These effects were short term.

"Using an objective measure, we saw a beneficial effect of inhaled cannabis on spasticity among patients receiving insufficient relief from traditional treatments," conclude the authors. "Although generally well-tolerated, smoking cannabis had acute cognitive effects. Larger, long-term studies are needed to confirm our findings and determine whether lower doses can result in beneficial effects with less cognitive impact."

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