The question of whether marijuana — produced from the flowering top of the hemp plant, Cannabis sativa — should be used for symptom management in multiple sclerosis (MS) is a complex one. It is generally agreed that better therapies are needed for distressing symptoms of MS — including pain, tremor and spasticity — that may not be sufficiently relieved by available treatments. Development of more treatments for MS symptoms is a priority for the National Society in its 2011-2015 strategic response. Still, there are uncertainties about the benefits of marijuana relative to its side effects. The fact that marijuana is an illegal drug in many states and by federal statute (see Supreme Court ruling below) further complicates the issue.
The Society supports the rights of people with MS to work with their MS health care providers to access marijuana for medical purposes in accordance with legal regulations in those states where such use has been approved. In addition, the Society supports advancing research to better understand the benefits and potential risks of marijuana and its derivatives as a treatment for MS.
In a study (e-published ahead of print April 30, 2014 in Neurology) to learn more about the impact of smoking cannabis on cognition in people with MS, researchers looked at the association between cognitive deficits and brain activity in 20 people who regularly smoked cannabis (but had not done so for at least 12 hours) and 19 non-cannabis users. The participants underwent functional magnetic resonance imaging (fMRI) while performing a memory test, which allowed the researchers to compare brain activity in the two groups. Participants were also given other tests of memory, information processing speed and attention. The results showed that people with MS who smoked cannabis performed less well on some of the cognitive tests and these findings were validated by fMRI results indicating abnormal patterns of brain activity during the performance of a memory task.
A large, placebo-controlled clinical trial involving 660 people with different forms of MS was conducted in Britain to determine whether taking capsules of extracts of marijuana and THC (tetrohydrocannabinol, an active ingredient in marijuana) could help control spasticity. The results from this study indicated that oral derivatives of marijuana did not provide objective improvement in spasticity (as measured by a standardized assessment tool). However, significantly more participants in the treatment group reported subjective improvements in spasticity and pain (but not in tremor or bladder symptoms). In other words, participants reported feeling improvements that could not be confirmed by the study physicians. These findings were further complicated by the fact that the study became unblinded: unpleasant side effects made it clear to many patients that they were receiving the active drug rather than the placebo.
Based on previous laboratory studies suggesting that certain types of cannabinoids may protect the nervous system, Dr. John Zajicek (Plymouth University Peninsula Schools of Medicine and Dentistry) and colleagues in the United Kingdom conducted a three-year clinical trial (CUPID) to test whether dronabinol (a synthetic Cannabis/marijuana derivative) slows progression in people with primary-progressive or secondary-progressive MS. The results of the trial, published in 2013 in Lancet Neurology showed that dronabinoal was unable to demonstrate a positive effect on disease progression.
In 2013 Dr. Zajicek also reported on the MUSEC study, which evaluated oral cannabis extract for treating muscle stiffness in 400 people with all types of MS. In this study muscle stiffness improved by almost twofold in the group taking cannabis extract compared to placebo, and improvements were also noted in body pain, spasms and sleep quality. The most frequent adverse events were urinary tract infections, dizziness, dry mouth and headache.
A controlled study found that nabiximols (Sativex®, GW Pharmaceuticals plc), an oral spray derived from Cannabis, significantly improved spasticity in a proportion of people with MS who had been identified as likely to respond to the therapy. Alena Novotna, MD, and colleagues in the Sativex Spasticity Study Group report these results in the European Journal of Neurology (2011 Mar 1, Epub ahead of print). Well-controlled clinical trials such as this one help sort out conflicting findings surrounding the use of cannabis and related products to treat MS symptoms. Sativex is now available in 11 countries and approved in an additional 13 countries – not including the United States – to treat MS-related spasticity.
Another study highlighted the impact of cannabis on cognition. Since MS can impair thinking, and previous studies suggest that smoking cannabis also impairs thinking, investigators at the University of Toronto investigated how cannabis use influenced cognition specifically in people with MS. Their study, published in Neurology (2011;76:1153-1160), measured cognitive function in 25 people with MS who regularly smoked or ingested street cannabis, compared to 25 people with MS who did not use cannabis. The users were tested at least 12 hours after last using cannabis so that intoxication was minimized. By matching the groups and also controlling for differences in terms of disease course and duration, age, gender, education and other factors, the cannabis users were found to perform significantly worse on measures of information processing speed, working memory, executive functions and other cognitive functions, and were twice as likely as nonusers to be considered “cognitively impaired.” The study confirmed for the first time that cannabis can worsen cognitive problems in MS.
Supreme Court ruling
On June 6, 2005, the Supreme Court ruled that the federal government has the power to prohibit and prosecute the possession and use of marijuana for medical purposes — even in the 20 states (Alaska, Arizona, California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Massachusetts, Michigan, Montana, Nevada, New Hampshire, New Jersey, New Mexico, Oregon, Rhode Island, Vermont and Washington) and Washington, D.C., where it is currently legal.
The decision overturned a 2003 ruling by a federal appeals court that shielded California’s Compassionate Use Act, the medical-marijuana initiative adopted by the state’s voters nine years ago, from federal drug enforcement. The appeals court had held that Congress lacked constitutional authority to regulate the noncommercial cultivation and use of marijuana that did not cross state lines.
In December 2014, the federal government ended its prohibition on the use of marijuana for medical purposes in fiscal year 2015 in those states where the use of marijuana had been approved for medical purposes before May 2014 (when the bill to end this prohibition was passed in Congress). Read more in Marijuana FAQs.