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About cannabis and MS

Cannabis is made up of compounds called cannabinoids. The main ones studied for their therapeutic effect are tetrahydrocannabinol (THC), which gets you ‘high’, and cannabidiol (CBD), which doesn’t.

Different types of cannabis

Recreational cannabis

Cannabis that’s grown and sold illegally comes in these main types:

  • Marijuana or ‘weed’ (the plant’s dried leaves and flowers). These days the most common type is skunk, a very strong strain of cannabis with high levels of THC.
  • Hash (the drug in its smokeable resin form).
  • Cannabis oils.

Depending on the type, the main ways you take it are by smoking, vapourising (breathing in after heating it) or eating it in things like cakes.

Unlicensed medicinal cannabis

There are products made using the CBD chemical found in cannabis. These include oils you take by mouth (for example, under your tongue or with a mouth spray) or by vapourising. They won’t get you high as they have little or no THC in them.

The law now says that these oils can be prescribed for medicinal use, but this is on a case-by-case basis and only when there is a special clinical need for individual people. You may see them still being sold as ‘food supplements’ (1).

It’s not against the law to have these products if they only have CBD in them (and no THC). (2)

Licensed medical cannabis

In the UK there are two cannabis-based drugs that have gone through trials and have a licence:

  • Nabilone (brand name Cesamet) – a drug cancer patients take to stop them feeling sick during chemotherapy. Nabilone has an artificial version of THC in it. It doesn’t have a licence to be used for MS but some doctors prescribe it for MS pain or muscle spasms.
  • Sativex (brand name for the drug nabiximols) - the only drug made from cannabis that’s licenced to treat spasticity (muscle spasms and stiffness) in MS. It’s a mouth spray made from an equal mix of THC and CBD.

As of late 2019 Sativex is available on the NHS in England and Wales for ‘moderate’ to ‘severe’ spasticity – if other treatments don’t work. We hope it’ll soon be available in Scotland and Northern Ireland, too.

Read more about Sativex

How cannabis can affect you

You can’t be sure how strong cannabis is when you buy it illegally or what it might be mixed with. So its effects might not always be the same. As well as the effects you might want, cannabis can cause less welcome changes:

  • dizziness
  • sleepiness
  • feeling drunk
  • impaired driving
  • feeling sick
  • anxiety
  • increased risk of seizures
  • harm to unborn babies

High doses may slow down reaction time, change your blood pressure and heart beat and affect your sight and coordination.

Smoking cannabis long term can affect your lungs and raise your heart attack and cancer risk. It’s possible to become dependent on cannabis, especially if you use it regularly.

If you or your family have a history of mental health problems (such as schizophrenia or bipolar disorder) using cannabis can trigger these or make them worse.

Smoking cannabis mixed with tobacco has the well-known risks of tobacco smoking but has extra risks for people with MS. Smoking tobacco can:

  • speed up how fast you go from relapsing MS to secondary progressive MS
  • make some MS drugs (disease modifying therapies) work less well.

Some studies of people with MS who regularly smoke cannabis show they do worse in tests measuring their memory and how fast they process information. MRI scans have also shown abnormal brain activity. None of this is seen in people who use the cannabis-based drug Sativex.

Research into cannabis

When they looked at the research in 2014, the American Academy of Neurology (AAN) didn’t find enough evidence that smoking cannabis was safe or effective against MS. They did find that people with MS said cannabis-based drugs (pills or sprays) helped with muscle stiffness (spasticity) and pain.(3)

A review by America’s National Academies of Sciences, Engineering and Medicine (NASEM) in 2017 found that patients who took cannabis-based treatment by mouth said it helped with their spasticity. (4) When their spasticity was tested it was less clear if it had got better.

Our medical advisors believe that about one in ten people with MS with pain or muscle spasticity might benefit from cannabis treatment, when other treatments for these symptoms have not worked. But smoking cannabis, especially if mixed with tobacco, is harmful to the health of people with MS.


> Read our report on cannabis and MS

  1. The Medicines and Healthcare products Regulatory Agency statement on products containing cannabidiol (CBD)
  2. Read 'Cannabis confusion – the legality of medicinal CBD in the UK' - on the Release website
  3. Visit the American Academy of Neurology website to read 'Medical marijuana in certain neurological conditions'. AAN: Minneapolis; 2014.
  4. Go to the US National Academies of Sciences, Engineering and Medicine website to read about 'The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research'. National Academies Press: Washington DC; 2017