Cannabis is a naturally occurring drug made from parts of the cannabis plant. It has been used throughout history both for medicinal and social purposes. However, at the present time cannabis is illegal to use in many countries, including the UK.
Cannabis contains many different compounds which are known as cannabinoids. The two cannabinoids most closely studied for a potential medicinal effect are tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is responsible for the high that is associated with cannabis use.
There has been a large body of research looking at the use of cannabis and cannabis based medicines in multiple sclerosis (MS), the results have been mixed.
Research into cannabis and cannabis based medicines
In 2014, the American Academy of Neurology (AAN) reviewed the available scientific studies on the safety and effectiveness of cannabis use in a range of neurological conditions, including MS. Two of the studies reviewed the use of smoked cannabis in MS - the first looked at its use to treat pain related to spasticity, whilst the second looked at safety. The report concluded the studies did not provide enough evidence to show whether smoked cannabis is safe or effective in MS.
However, the AAN report concluded that cannabis based medicines in pill or spray form can help to treat certain MS symptoms such as spasticity and spasms, lessen central pain (feelings of burning, pins and needles or numbness) and may lessen frequent urination.
More recently, the US National Academies of Sciences, Engineering and Medicine (NASEM) reported on the health effects of cannabis and cannabinoids following a review of the evidence, with a particular focus on research published since 2011. Their conclusion was that for the majority of conditions there was inadequate evidence to assess the effects of cannabis. However, they did find sufficient evidence that adults with chronic pain treated with cannabis were more likely to experience a clinically significant reduction in pain symptoms.
The NASEM report also confirmed that in adults with MS-related spasticity, short-term use of oral cannabis based medicines could improve patient-reported spasticity symptoms. They also concluded there was some evidence that cannabinoids may help improve short-term sleep in people with some conditions, including chronic pain and MS.
Cannabis research in the UK
The CAMS study, which involved 660 participants around the UK, looked at the effect of oral cannabis extract or THC on various symptoms of MS, primarily on spasticity. Results of this study were mixed, with no significant effect on spasticity as measured by the Ashworth scale. However, some improvement was shown on the time taken to complete a 10-metre walk and patient satisfaction scores were positive.
The CUPID research trial began in 2006 and involved 493 people at centres around the UK. The MS Trust funded the cost of the MRI scans that were taken. It looked at whether tetrahydrocannabinol (THC), one of the active ingredients in cannabis might have a role in protecting the brain from damage by multiple sclerosis, a concept called neuroprotection. The results of the study were published in 2013. It found that there was no difference between participants who took the cannabis based medicine and those on placebo, with the treatment having no overall effect on the rate of progression. Other outcome measures included whether THC provides symptomatic relief for spasticity. The trial also tried to assess the long-term safety of cannabis-based medicines.
The MUSEC trial, which reported in 2012, involved 279 people taking a cannabis based pill or placebo. The trial showed higher proportions of people on the active treatment reported reductions in muscle stiffness, spasms and pain and improved sleep quality.
Sativex is a cannabis based mouth spray. It is licensed as an add-on treatment for moderate to severe MS spasticity in people who receive inadequate relief from the standard oral anti-spasticity medicines or have experienced unbearable side effects whilst taking these medicines.
Although Sativex has been licensed in the UK, it has not been approved by the National Institute for Health and Care Excellence (NICE) or the Scottish Medicines Consortium (SMC), therefore it is not readily available on the NHS in England or Scotland. Sativex has been approved for use on the NHS in Wales by the All Medicines Strategy Group (AWMSG), however it can still be difficult to obtain.
Despite evidence that cannabis may have some medical benefits, including for people with MS, it has been linked to mental health problems such as anxiety, memory loss, panic attacks and psychotic episodes. There is also the risk of addiction in a small proportion of users. Since short-term memory and processing speed can be impaired in many people with MS, and given that cannabis has been shown to impair cognition in healthy subjects, there is some concern that the use of cannabis could worsen cognitive difficulties in people with MS.
Legal status of cannabis
A growing number of countries including Germany, Spain, the Netherlands and some American states have legalised access to medicinal cannabis. In the UK cannabis is a Class B drug and, other than its use in medical trials or in the form of Sativex, it is illegal to possess, cultivate or supply cannabis. The maximum penalty for possession is five years in prison plus an unlimited fine. The maximum penalty for supplying cannabis is 14 years in prison and an unlimited fine.
- Lancet 2003;362(9395):1517-1526. Summary Cannabinoids for treatment of spasticity and other symptoms related to multiple sclerosis (CAMS study): multicentre randomised placebo-controlled trial.
- Lancet Neurology 2013;12(9):857-865. Summary Effect of dronabinol on progression in progessive multiple sclerosis (CUPID): a randomised placebo-controlled trial.
- Journal of Neurology Neurosurgery and Psychiatry 2012;83(11):1125-1132. Summary Multiple sclerosis and extract of cannabis: results of the MUSEC trial.
- Current Neuropharmacology 2016; Oct 31 [Epub ahead of print] Summary Pros and cons of medicinal cannabis use by people with chronic brain disorders.
- Multiple Sclerosis Journal 2015;21(14):1755-1760. Summary What to make of cannabis and cognition in MS: in search of clarity amid the haze.
- NeuroImage: Clinical 2015;8:140-147. Summary Multiple sclerosis, cannabis and cognition: a structural MRI study.
- Neurology 2014;82(21):1879-1887. Summary Effects of cannabis on cognition in patients with MS: a psychometric and MRI study.
- AAN: Minneapolis; 2014. Patient summary Medical marijuana in certain neurological conditions.
- Health Technology Assessment 2015 Feb;19(12):vii-viii, xxv-xxxi, 1-187 Summary The Cannabinoid Use in Progressive Inflammatory brain Disease (CUPID) trial: a randomised double-blind placebo-controlled parallel-group multicentre trial and economic evaluation of cannabinoids to slow progression in multiple sclerosis.
- National Academies Press: Washington DC; 2017. Full report The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research.
- MS patient 'frustrated' over access to Sativex. BBC news item January 2017.
Last updated: November 2017
Last reviewed: February 2017
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