Scientists Review State of Cannabis Research in MS

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Treatment with cannabis-based medications may ease muscle spasms, decrease pain, and aid in sleep for people with multiple sclerosis (MS), but more research is needed to evaluate the potential benefits of cannabis use.

That is the finding of a team of U.S. researchers who published a review paper, “Neurological Benefits, Clinical Challenges, and Neuropathologic Promise of Medical Marijuana: A Systematic Review of Cannabinoid Effects in Multiple Sclerosis and Experimental Models of Demyelination,” in the journal Biomedicines.

The cannabis plant has been used by humans for millennia, both recreationally and medicinally. Cannabis has two main biologically active ingredients: tetrahydrocannabinol (THC), which is chiefly responsible for the “high” associated with cannabis use, and cannabidiol (CBD), which does not induce a “high” but is thought to have anti-anxiety and anti-inflammatory effects.

In recent years, there has been renewed interest in the potential of cannabis-based therapies to ease symptoms of MS and other chronic conditions. Here, researchers conducted a review of scientific studies on MS and cannabis that were published over the past 15 years.

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The review included a total of 28 studies. Half of the studies evaluated cannabis-based therapies in mouse models of MS. Broadly, findings from these preclinical studies have been promising, suggesting that cannabis therapies can lessen inflammation, protect nerves from damage, and ease spasticity. The therapies also promoted remyelination, the repair of the fatty myelin sheath that is damaged in MS.

“The experimental results combined adequately demonstrate that cannabinoid treatments are effective in diminishing clinical disease severity, alleviating hindlimb stiffness, facilitating recovery, improving motor function, strengthening anti-inflammatory responses, … and promoting remyelination in the [nervous system],” the researchers wrote.

Though results in animal models were generally consistent across studies, the researchers noted there are important differences in the cannabis-sensitive biological systems in mice and people, so the validity of these results in humans “is less certain.”

The other 14 studies were conducted with human participants. Most of them evaluated Sativex (nabiximols), an oral spray containing THC and CBD that is approved to treat MS-related spasticity in the European Union, the U.K., and Canada, though not in the U.S. Sativex is marketed by Jazz Pharmaceuticals, which was not involved in this study.

Nine of the in-human studies assessed the effect of cannabis-based treatments on spasticity (muscle spasms) in 1,582 people with MS. Results showed that patients reported less spasticity with the treatment, as evidenced by an average decrease of 2.8 points on patient-rated spasticity (on a scale from 0 to 10), with a follow-up time of up to a year.

Five studies evaluated pain-related outcomes in 573 people with MS. Average pain scores were lowered significantly, by 3.42 points, at four weeks after starting treatment. In one study, the easing in pain lasted at least six months.

Three studies assessed sleep-related outcomes in 816 participants, and results generally showed that cannabis-based treatment could improve sleep quality. Another three studies that assessed the effect of treatment on urinary incontinence in 235 people showed no significant effect of treatment, though some modest decreases in the frequency and urgency of daily urination was noted.

Across all these studies, the researchers noted, there were responders and non-responders — that is, some patients appeared to derive a clear benefit from cannabis-based treatment, while others showed no signs of benefiting. The researchers noted that non-responders often dropped out of studies, ultimately meaning the studies had less statistical power to detect meaningful effects.

The researchers also noted that placebo effects often were seen in studies with available placebo groups, so the benefits seen in studies lacking a control group “were most likely overestimates.” They stressed the need for well-controlled future studies to tease out the contribution of placebo effect in response to cannabis therapies.

Overall, the team concluded, current evidence suggests that “the magnitudes of effects [from treatment with cannabis-based therapies] on short-term neurological outcomes in MS patients are either small, limited, or moderate, and that the benefits are more easily detected by subjective rather than objective measures.”

“To increase confidence in the efficacy of medical marijuana as an add-on therapy in MS, higher-quality, multi-year, randomized, double-blind, placebo-controlled clinical trials are warranted to assess long-term tolerability, [and] drug–drug interactions [as well as] benefits for preventing breakthrough relapses, ability to reverse deficits or retard the accrual of disability, and the impact on measures of quality of life,” they added.

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