Medical Marijuana in Neurology

Everyone on the internet seems to have an opinion about medical marijuana.  Some claim it’s an excuse for stoners to get high.   Others claim it’s a miracle drug  kept under wraps by Big Pharma so they can peddle more dangerous and less effective treatments. I suspect most people, though, are just trying to find some truth amidst a lot of spin.

As a doctor, I view marijuana as I do any drug-- it may have potential to help or harm, depending on how it's used.

 Opiate is likely to help certain disorders, and we should be able to know what those disorders are and prescribe it to people who truly need it.  Like other drugs, though, we must be aware of side effects and cautious about the potential for abuse. 

The trouble is that there isn’t much quality information on marijuana.  Who was going to fund the studies while it was illegal?  Even now, with some states having legalized marijuana use, can you imagine the federal government funding such a study?  So we have usually have to make due with suboptimal research.

That said, let’s go forward first with what we know about marijuana with some confidence.

Potential Benefits:

Multiple Sclerosis Symptoms: Oral cannabis extract (not smoked) has been clearly shown to be effective in reducing patient reported scores of pain or painful spasms after 12 to 15 weeks.  That said, there is just as good evidence that the extract doesn’t seem to help objective measurements such as the physical examination.

  Conversely, nabiximols (another cannabis extract) can reduce the number of time someone with MS and bladder complaints has to use the restroom, but doesn’t lead to reports of improvement by patients. 

Movement Disorders:  There’s really not much evidence that cannabis or related products help symptoms in Huntington’s disease or Parkinson’s disease.

  In fact, there’s some evidence that shows it isn’t helpful in helping Parkinson’s disease dyskinesia. 

Epilepsy: This is a hotly contested area, as there are some compelling reports of seizures, not treatable by any other means, which improve with marijuana products.    Early results from one well designed study suggests that seizures may be reduced by up to 54% in children treated with a purified cannabis extract. This shouldn’t be taken as saying marijuana is good for all seizures—some prescribed anti-epileptic drugs can make certain seizures worse.  The thing is, we know what those seizure types are, because those drugs are very well studied, unlike marijuana.

Anxiety: While it’s considered more a “psychiatric” than “neurological” disorder, this division is ultimately artificial.  Anxiety can make a lot of neurological symptoms worse, and a lot of neurological symptoms cause anxiety.  And yes, at least anecdotally, marijuana makes people feel less anxious.  That’s the reason why many use the drug recreationally.

  That said, this is a very short term fix, there are other better understood medications available, and if your anxiety is so severe that you feel you need a medication like marijuana, you probably need more professional help like a psychiatrist or therapist. 

There is also some evidence to suggest that cannabinoids are useful with nausea and vomiting due to chemotherapy, sleep disorders, and Tourette syndrome, though this evidence is not extremely strong. 


Some believe marijuana to be perfectly harmless.  Some consider it to be the gateway to all that is evil.  Both positions are wrong.

For one, the cognitive effects of marijuana, especially when high, are very well known.   It’s probably not a drug you want to use if you are doing mentally challenging work, or if you’re concerned about your memory or thinking already. 

The long-term effects of marijuana on memory and cognition are more debated.  The most concerning evidence involves use by children and adolescents. Some studies even associate marijuana use with an increased risk of schizophrenia.  While this may be rare, it’s probably best to avoid use of marijuana in children and adolescents, unless there is a clear medication need.

Other, more transitory side effects include dry mouth, nausea, somnolence, euphoria, disorientation, drowsiness, weakness, mood changes, hallucinations and dizziness. Also, note that all the putative medical therapies above have not involved smoking marijuana, but taking it by other routes.


At this point, medical marijuana should only be considered when standard-of-care treatments have proven ineffective.  As more data becomes available, the role of medical marijuana will probably expand.   In the meantime, it is important to neither get swept away by hype, testimonials or marketing, and at the same time to also avoid rigid or paranoid thinking. 


Leon French, Courtney Gray, Gabriel Leonard,  Michel Perron, Bruce Pike, et al. Early Cannabis Use, Polygenic Risk Score for Schizophrenia and Brain Maturation in Adolescence.  JAMA Psychiatry. Published online August 26, 2015. doi:10.1001/jamapsychiatry.2015.1131

Penny F. Whiting, Robert F. Wolff,  Sohan Deshpande,  Marcello Di Nisio, Steven Duffy, Cannabinoids for Medical Use: A Systematic Review and Meta-analysis. JAMA. 2015;313(24):2456-2473. doi:10.1001/jama.2015.6358.

Selim R Benbadis, Juan Sanchez-Ramos, Ali Bozorga, Melissa Giarratanoa, Kavita Kalidasa. Medical marijuana in neurology. Volume 14, Issue 12, 2014

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