Key messages

• Treatment with nabiximols likely results in improvement of spasticity and may not increase serious harmful effects compared with placebo
• Compared with placebo, cannabinoids (nabiximols, Cannabis extract, synthetic cannabinoids) likely improve well‐being when measured with patient‐reported outcomes 
• Due to a lack of robust evidence, the benefit of these medicines for treating chronic neuropathic pain is unclear.

What is the issue? Many people with multiple sclerosis (MS) experience spasticity that causes also pain and impacts on the ability to carry out daily activities. Spasticity is a form of increased muscle tone. Cannabis‐based medicines refer to the use of Cannabis, or its ingredients called cannabinoids, as medical therapies to alleviate spasticity, chronic pain and other symptoms in MS. An international survey found that MS was one of the five medical conditions for which Cannabis was most often used. Another survey conducted in the UK found that more than one in five people with MS reported they had used Cannabis to try to manage their symptoms. 

What did we find? We found 25 studies that involved 3763 people with MS, 2290 of whom received cannabinoids. Fifteen studies were very short term or short‐term studies (two to 12 weeks), seven were intermediate term (12 to 26 weeks), and two were long term (50 and 156 weeks). One study reported results at three days only. The biggest study was conducted in 657 people and the smallest study involved 14 people. Most studies were done in European countries. Thirteen studies evaluated an oral spray (nabiximols) containing two compounds derived from the Cannabis plant. The other studies compared different cannabinoids with placebo. Pharmaceutical companies funded 15 of the studies.

Main results

Compared with placebo, cannabinoids: 

• probably increase the number of people who report an important reduction of perceived severity of spasticity for up to 14 weeks (evidence from five studies in 1143 people);
• may increase the number of people who report an important reduction of perceived severity of chronic neuropathic pain, but the evidence is very uncertain (evidence from one study in 48 people).

We are uncertain whether cannabinoids reduce chronic neuropathic pain intensity:

• probably increase the number of people who perceive their well‐being as 'very much' or 'much' improved (evidence from eight studies in 1215 people);
• may increase slightly the number of people who discontinue treatment due to unwanted effects (evidence from 21 studies in 3110 people);
• may result in little to no difference in the number of people who have serious harmful effects (evidence from 20 studies in 3124 people);
• may increase nervous system disorders (evidence from seven studies in 1154 people) or psychiatric disorders (evidence from six studies in 1122 people);
• may have little to no effect on the number of people who have drug tolerance, but the evidence is very uncertain (two studies in 458 people).

What are the limitations of the evidence?

There is no high‐quality evidence. 

We are moderately confident that cannabinoids work better versus no cannabinoids to improve severity of spasticity and well‐being in adults with MS. We have little confidence in our results for the effect on chronic neuropathic pain because the available evidence is limited.

There is limited evidence to determine the effects of cannabinoids on serious harmful effects, nervous system or psychiatric disorders, and drug tolerance.