Science: How marijuana works to help those with multiple sclerosis

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Multiple sclerosis (MS) is a neurological disease in which the immune system attacks the fatty protein that protects nerve cells. The exposed and damaged (i.e. “sclerotic”) nerves lose their ability to transmit signals, and this results in a wide array of bad results, including numbness, dizziness, itching and blurred vision. More than half of people who suffer from MS experience pain, muscle stiffness or spasticity, and cognitive impairment.

It’s those last three symptoms that have been most studied in relation to medical marijuana.

What’s the Good News?

Cannabis eases spasticity and muscle stiffness

In double-blind, placebo-controlled trials, MS patients who use cannabis oil, synthetic THC or an oral-spray blend of THC and CBD have reported feeling relief from muscle stiffness and spasms. At least one has shown a “highly significant” difference in spasticity between cannabis users and nonusers. Another quantified that difference as an almost two-fold improvement.

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In double-blind, placebo-controlled trials, MS patients who use cannabis oil, synthetic THC, or an oral-spray blend of THC and CBD have reported feeling relief from muscle stiffness and spasms. PABLO PORCIUNCULA BRUNE/AFP/Getty Images

What is felt, however, is not necessarily what can be proven. Despite patients reporting strong improvementsa European study from 2005 could only determine a “small treatment effect” by objective measures.

And there’s more:

The same studies found reduced pain and improved sleep.

What’s the Bad News?

Weed can addle your brains

In the past five years, the first studies to specifically examine the effect of cannabis on the mental clarity of MS patients have emerged. And they confirm that cannabis can worsen the cognitive problems caused by the disease. A small study from 2011 concluded that patients who treated their MS with “street cannabis” (how charmingly lurid!) experienced “significantly worse” mental functions, such as processing speed, memory and executive functions. They were also twice as likely as non-users to be cognitively impaired. An even smaller study from 2014 found similar results.

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In the past five years, the first studies to specifically examine the effect of cannabis on the mental clarity of MS patients have emerged. PABLO PORCIUNCULA BRUNE/AFP/Getty Images

What do the pros say?

  • In a 2014 overview of the medical literature, the American Academy of Neurology (AAN) concluded that cannabis oil, synthetic THC and THC-CBD blend oral spray are all “probably effective” to treat the “patient-reported” spasticity and pain of MS. As for smoked pot, there’s not yet enough evidence for the AAN to decide.
  • The National Multiple Sclerosis Society supports access to medical marijuana and more research on potential benefits and harms of using the drug to treat MS.
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