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. Still, there are uncertainties about the benefits of marijuana relative to its side effects.
The Society supports the rights of people with MS to work with their MS healthcare 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.
On effects of cannabis on cognition / cognitive function
in people with MS:
- 20 subjects with MS who smoked cannabis and 19 noncannabis users with MS, matched on demographic and neurologic variables, underwent functional magnetic resonance imaging (fMRI, which measures patterns of brain activity during performance of a task) while completing a test of working memory. The cannabis group performed more poorly on the more demanding tasks. (Neurology, 2014)
- 25 people with MS who regularly smoked or ingested street cannabis were tested and results compared to 25 people with MS who did not use cannabis. Users were tested at least 12 hours after last using cannabis so that intoxication was minimized. (Groups were matched and also differences were controlled for 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. (Neurology, 2012)
On oral cannabis/extract effect on spasticity
and/or muscle stiffness:
- MS and Extract of Cannabis (MUSEC): Participants with stable MS were randomly assigned to receive oral cannabis extract (144 people) or placebo (135 people), and reported their perceptions of changes in muscle stiffness before and after 12 weeks of treatment. Muscle stiffness improved by almost twofold in the group taking cannabis 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; no new safety concerns were observed. (NIH, 2012)
- Nabiximols—an oral spray derived from cannabis—(Sativex®, GW Pharmaceuticals) significantly improved spasticity in a proportion of people with MS who had been identified as likely to respond to the therapy. Well-controlled clinical trials such as this one help sort out conflicting findings surrounding the use of marijuana and related products to treat MS symptoms. Sativex is now available in 15 countries and approved in an additional 12 countries—not including the United States—to treat MS-related spasticity. (European Journal of Neurology, 2011)
- Effectiveness and long-term safety of cannabinoids in MS: 630 subjects with stable MS and muscle spasticity, from 33 UK centers, were randomly assigned to receive oral THC (tetrohydrocannabinol, an active ingredient in marijuana) , cannabis extract or placebo over 15 weeks. 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. (Journal of Neurology, Neurosurgery & Psychiatry, 2005)
On progression of MS: Effect of oral dronabinol (a synthetic Cannabis/marijuana derivative) on progression in progressive MS: Previous laboratory evidence has shown that cannabinoids might protect the nervous system. In this study, 329 people received at least one dose of dronabinol and 164 received at least one dose of placebo. Dronabinol had no overall effect on the progression of MS. (Lancet Neurology
Guideline from American Academy of Neurology
The American Academy of Neurology (AAN), an association of neurologists and neuroscientists dedicated to promoting high-quality care for people with nervous system disorders, released a “Summary of evidence-based guideline: Complementary and alternative medicine in MS
” in 2014, including the following conclusions on the evidence regarding marijuana and its derivatives:
Read more in FAQs.
- Oral cannabis extract and synthetic THC (tetrahydrocannabinol — a major active component of cannabis) are probably effective for reducing patient-reported symptoms spasticity and pain, but not MS-related tremor or spasticity measured by tests administered by the physician. For these cannabis derivatives the most commonly reported side effects were dizziness, drowsiness, difficulty concentrating and memory disturbance.
- Sativex oral spray (GW Pharmaceuticals) is probably effective for improving patient-reported symptoms of spasticity, pain and urinary frequency, but not bladder incontinence, MS-related tremor or spasticity measured by tests administered by the physician.
- Smoked cannabis research studies have not produced enough evidence to assess its safety or effectiveness for treating MS symptoms including spasticity, pain, balance, posture and cognition changes.
- The long-term safety of marijuana use for MS symptom management is not yet known.
Although marijuana is illegal at the federal level, federal legislation passed in 2015 clarified that the federal government would no longer use federal funds to enforce federal marijuana laws in states that permit medical marijuana use. This should reduce confusion in those states listed in the legislation where the use of marijuana was approved for medical purposes before May 2014.
This legislation overturned the Supreme Court’s 2005 ruling that the federal government could prohibit and prosecute the possession and use of marijuana for medical purposes—even in the states where it was legal.
Read more in FAQs.