Wednesday, May 16, 2012

A Look at the Recent Study of Cannabis and Multiple Sclerosis

Smoked marijuana reduced spasticity in a small trial of MS patients.

The leading wedge of the medical marijuana movement has traditionally been centered on pot as medicine for the effects of chemotherapy, for the treatment of glaucoma, and for certain kinds of neuropathic pain. From there, the evidence for conditions treatable with marijuana quickly becomes either anecdotal or based on limited studies. But pharmacologists have always been intrigued by the notion of treating certain neurologic conditions with cannabis. Sativex, which is sprayed under the tongue as a cannabis mist, has been approved for use against multiple sclerosis, or MS, in Canada, the UK, and some European countries. (In the U.S., parent company GW Pharma is seeking FDA approval for the use of Sativex to treat cancer pain).

There is accumulating evidence that cannabinoid receptors may be involved in controlling spasticity, and that anandamide, the brain’s endogenous form of cannabis, is a specific antispasticity agent.

Additional evidence that researchers may be on to something appeared recently in the Canadian Medical Association Journal. Dr. Jody Corey-Bloom and coworkers at the University of California in San Diego conducted a small, placebo-controlled trial with adult patients suffering from poorly controlled spasticity. Thirty participants were randomly divided into two groups. Those in the first group were given a daily joint, and those in the second group received “identical placebo cigarettes.” After three days, the investigators found that smoked marijuana resulted in a reduction in treatment-resistant spasticity, compared to placebo.

Clearly, it’s hard for a study of this sort to be truly blind: Participants, one presumes, had little trouble distinguishing the medicine from the placebo. And in fact, an appendix to the study shows this to be true: “Seventeen participants correctly guessed their treatment phase for all six visits… For the remaining participants, cannabis was correctly guessed on 33/35 visits.” This raises the question of various kinds of self-selection bias and expectancy effects, and the study authors themselves write that the results “might not be generalizable to patients who are cannabis-naïve.” On the other hand, cannabis-naïve patients were in the minority. The average age of the participants was 50, and fully 80% of them admitted to previous “recreational experience” with cannabis. (I don’t have a good Baby Boomer joke for the occasion, but if I did, this is where it would go).

I asked Dr. Corey-Bloom about this potential problem in an email exchange: “The primary outcome measure was the Ashworth Spasticity Scale, which is an objective measure, carried out by an independent rater,” she wrote. “Their job was just to come in and feel the tone around each joint (elbow, hip, knee), rate it, and leave.  That's why we think it was so important to have an objective measure, rather than just self-report.”

With all this in mind, the study found that “smoking cannabis reduced patient scores on the modified Ashworth scale by an average of 2.74 points.” The authors conclude: “We saw a beneficial effect of smoked cannabis on treatment-resistant spasticity and pain associated with multiple sclerosis among our participants.”

Other studies have found similar declines in spasticity from cannabinoids, but have tended not to use marijuana in smokable form.

Corey-Bloom, J., Wolfson, T., Gamst, A., Jin, S., Marcotte, T., Bentley, H., & Gouaux, B. (2012). Smoked cannabis for spasticity in multiple sclerosis: a randomized, placebo-controlled trial Canadian Medical Association Journal DOI: 10.1503/cmaj.110837

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