What's Hot in PD? Everything You Need to Know About Medical Marijuana and Parkinson’s Disease

There has been a recent and evolving media blitz concerning the potential use of medical marijuana (tetrahydrocannabinol, THC) among the Parkinson’s disease (PD) community. All of the attention to marijuana has been largely a result of multiple states passing legislation to legalize and to regulate the drug, or to alternatively make it available for select medical diagnoses. In this month’s What’s Hot in PD? column, I will review the current state of the research into medical marijuana for Parkinson’s disease.

A recent report from the guideline development subcommittee of the American Academy of Neurology (AAN) tackled the evidence-base supporting the use of marijuana for neurological disorders. Spasticity, central pain syndromes and bladder dysfunction (disorders not including Parkinson’s ) seemed to be improved with marijuana use. The few available studies revealed that marijuana was not helpful in Parkinson’s-related tremor or levodopa-induced dyskinesias. The report was careful to outline the risks and the benefits of medical marijuana, and it recommended education and counseling for anyone considering this option. The risk of serious psychopathologic effects (hallucinations, etc.) was cited to be about 1%. 

In addition to the AAN report, there have been a few recent papers supporting the use of marijuana for specific Parkinson’s disease symptoms (motor, mood, quality of life, sleep), however, all have suffered from methodological issues such as including small numbers of patients, and not including a proper control group. Katerina Venderova in 2004 (Movement Disorders Journal) conducted a survey of Parkinson’s disease patients on marijuana (cannabis) and reported that “39 patients (45.9%) described mild or substantial alleviation of their PD symptoms in general, 26 (30.6%) showed improvement of rest tremor, 38 (44.7%) had improvement in bradykinesia, 32 (37.7%) had alleviation of muscle rigidity, and 12 (14.1%) had improvement of L-dopa-induced dyskinesias.

Only 4 patients in this survey (4.7%) reported that cannabis actually worsened their symptoms. Patients using cannabis for at least 3 months reported significantly more alleviation of their Parkinson’s disease symptoms in general.” Like Venderova who conducted her survey in Prague, we have also had people with PD call our free 1-800-4PD-INFO Helpline, and detail personal experiences and positive stories supportive of marijuana in Parkinson’s disease. Collectively, the problem with all of these types of personal reports has been the lack of scientific rigor necessary to truly understand the effects of marijuana on Parkinson’s.

In a recent review in the New England Journal of Medicine, the National Institute on Drug Abuse (NIDA) Director Dr. Nora Volkow carefully outlined the adverse health effects of marijuana use. In her article, Dr. Volkow pointed out that marijuana, which is thought of by much of the public as a completely harmless drug, can have serious adverse effects. She makes the following important points:

  • In the U.S. it is the most commonly used “illicit” drug
  • 12% of those 12 years or older used it in the past year
  • Smoking is the most common way people use marijuana and this can harm the lungs
  • There are available edible forms including teas and foods
  • Approximately 9% of users will become addicted, and there may be a withdrawal syndrome which can make quitting difficult for some users
  • Use in adolescence and early adulthood can contribute to worsening brain function, decreased connections between brain regions, and a decrease in IQ
  • Heavy marijuana use can rarely lead to psychosis and hallucinations
  • Marijuana can reduce cognitive and also worsen motor function
  • Your risk of a car accident doubles if you have recently smoked marijuana
  • The potency of the THC content in marijuana has increased from 3% to 12% in the last several decades making accidental overdoses, especially with food products, much more common
  • The best evidence supporting marijuana use has been shown in glaucoma, nausea, the AIDS wasting syndrome, chronic pain, multiple sclerosis, and epilepsy

Scientifically it is not crazy to think that marijuana may play some positive role in the alleviation of Parkinson’s disease symptoms. There are cannabinoid (THC) receptors all over the brain, and these receptors seem to be concentrated in a region important to Parkinson’s disease, commonly referred to as the basal ganglia. In fact, the globus pallidus and the substantia nigra pars reticulata, which are structures within the basal ganglia, are some of the most densely packed cannabinoid (THC) receptor areas in the human body. It is therefore not beyond reason to think that a drug directed at these receptors might positively influence the symptoms of Parkinson’s disease. Indeed, many drug companies remain interested in compounds influencing these receptors.

What is the bottom line for information that a person with Parkinson’s disease will need to know if considering medical marijuana? Marijuana should never be thought of as a replacement for dopaminergic and other approved therapies for Parkinson’s disease. Second, though most available large studies have not shown a benefit, that does not mean that there will not be a benefit. Much more research will be needed to understand which patients, which symptoms, and how best to safely administer medical marijuana in Parkinson’s disease, especially over the long-term. It may turn out that non-motor features such as depression, anxiety, and pain respond best, but studies are desperately needed to sort this out. Parkinson’s disease patients living in states where marijuana has been legalized for medical use should be aware of the dangers outlined by Dr. Volkow, particularly the effects on the lungs, the dangers of driving, and accidental overdoses (particularly with food items). Finally, states will need to develop training programs for doctors and medical teams prescribing marijuana, so that the Parkinson’s disease patient on medical marijuana can be kept as safe as possible.

Selected References for Medical Marijuana and Parkinson’s Disease

Chagas MH, Eckeli AL, Zuardi AW, Pena-Pereira MA, Sobreira-Neto MA, Sobreira ET, Camilo MR, Bergamaschi MM, Schenck CH, Hallak JE, Tumas V, Crippa JA. Cannabidiol can improve complex sleep-related behaviours associated with rapid eye movement sleep behaviour disorder in Parkinson's disease patients: a case series. J Clin Pharm Ther. 2014 May 21. doi: 10.1111/jcpt.12179. [Epub ahead of print] PubMed PMID: 24845114.

Koppel BS, Brust JC, Fife T, Bronstein J, Youssof S, Gronseth G, Gloss D. Systematic review: efficacy and safety of medical marijuana in selected neurologic disorders: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology. 2014 Apr 29;82(17):1556-63. doi: 10.1212/WNL.0000000000000363. Review. PubMed PMID: 24778283; PubMed Central PMCID: PMC4011465.

Lotan I, Treves TA, Roditi Y, Djaldetti R. Cannabis (medical marijuana) treatment for motor and non-motor symptoms of Parkinson disease: an open-label observational study. Clin Neuropharmacol. 2014 Mar-Apr;37(2):41-4. doi: 10.1097/WNF.0000000000000016. PubMed PMID: 24614667.

Gowran A, Noonan J, Campbell VA. The multiplicity of action of cannabinoids: implications for treating neurodegeneration. CNS Neurosci Ther. 2011 Dec;17(6):637-44. doi: 10.1111/j.1755-5949.2010.00195.x. Epub 2010 Sep 28. Review. PubMed PMID: 20875047.

Iuvone T, Esposito G, De Filippis D, Scuderi C, Steardo L. Cannabidiol: a promising drug for neurodegenerative disorders? CNS Neurosci Ther. 2009 Winter;15(1):65-75. doi: 10.1111/j.1755-5949.2008.00065.x. Review. PubMed PMID: 19228180.

McSherry JW. Cannabis for dyskinesia in Parkinson disease: a randomized double-blind crossover study. Neurology. 2005 Mar 22;64(6):1100; author reply 1100. PubMed PMID: 15781848.

Carroll CB, Bain PG, Teare L, Liu X, Joint C, Wroath C, Parkin SG, Fox P, Wright D, Hobart J, Zajicek JP. Cannabis for dyskinesia in Parkinson disease: a randomized double-blind crossover study. Neurology. 2004 Oct 12;63(7):1245-50. PubMed PMID: 15477546.

Venderová K, Růzicka E, Vorísek V, Visnovský P. Survey on cannabis use in Parkinson's disease: subjective improvement of motor symptoms. Mov Disord. 2004 Sep;19(9):1102-6. PubMed PMID: 15372606.

Volkow ND, Baler RD, Compton WM, Weiss SR. Adverse health effects of marijuana use. N Engl J Med. 2014 Jun 5;370(23):2219-27. doi: 10.1056/NEJMra1402309. Review. PubMed PMID: 24897085.


You can find out more about our National Medical Director, Dr. Michael S. Okun, by also visiting the Center of Excellence, University of Florida Health Center for Movement Disorders and Neurorestoration. Dr. Okun is also the author of the Amazon #1 Parkinson's Best Seller 10 Secrets to a Happier Life and 10 Breakthrough Therapies for Parkinson's Disease.

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