Reviewed by Danny Bega, MD, MSCI, Movement Disorder Specialist and Associate Professor of Neurology at Northwestern University Feinberg School of Medicine.
One of the most common questions people with Parkinson’s ask is, “What about medical marijuana?” Many are curious if and how it might work for different symptoms, and what the research says.
As an increasing number of states authorize medical (and even recreational) marijuana, a significant number of people with Parkinson’s disease (PD) report using these products. Some describe benefit on sleep, tremor or other symptoms. Others report side effects. And many say they are unsure how to discuss with their physician.
Here, we offer general information about cannabis and Parkinson’s, tips for talking with your doctor, and more.
What is medical marijuana?
Marijuana comes from the Cannabis plant, which contains hundreds of different components, including cannabinoids. Cannabinoids bind to receptors throughout the brain and body to influence movement, mood, inflammation and other activities. Many of these receptors are in areas of the brain impacted by Parkinson’s disease (the basal ganglia).
The main cannabinoid is tetrahydrocannabinol (THC). This can cause the feeling of being “high”—described as happiness, amusement or contentment — that is commonly associated with marijuana. THC may help nausea, pain or muscle spasms, but it also can have negative effects on mood, behavior and thinking. The second most common cannabinoid, cannabidiol (CBD), seems to have less effect on thinking, memory or mood.
What is cannabis?
Cannabis refers to products from the Cannabis plant, including marijuana.
Cannabis comes in several forms and can be taken different ways: smoking or vaping dried leaves, swallowing pills or eating or drinking foods (edibles) that contain cannabinoids, putting liquid or drops under the tongue, or applying creams or ointments to your skin (on painful areas, for example). Two U.S. Food and Drug Administration (FDA)-approved prescription cannabis medications also are available for specific conditions, such as epilepsy or cancer- or AIDS-related symptoms.
The amount of THC, CBD, other cannabinoids and other (sometimes unknown) substances varies across products. Sometimes, the levels of these contents may not be known. And even if the product does have a label, studies have shown the label may not fully or accurately represent what’s inside. (There are no federal regulations governing standards of purity or label accuracy. Most states have their own regulations, but these vary.)
Still, it’s important to read labels, ask questions, and have a general idea of the amount of THC or CBD in the product. For those who choose to try cannabis, use caution — start with a low dose and increase slowly (if at all). Much of this is trial and error because solid studies on dosing and formulation are lacking. (See below.)
Is cannabis safe? Effective?
There are many anecdotal reports of benefit. But controlled trials — on motor and non-motor symptoms as well as dyskinesia (involuntary, uncontrolled movement) — have not yet proven the safety or benefits of cannabis in Parkinson’s.
Clinical trials have generally had mixed or conflicting results (some positive, some negative). On questionnaires, people often report benefit on pain, sleep, mood, or motor symptoms such as tremor or stiffness. But many also report side effects. This leaves patients, doctors and researchers with insufficient evidence to guide use.
In low doses, cannabinoids appear to be relatively well tolerated. But, like all treatments, they have potential side effects: new or worsened nausea; dizziness; weakness; hallucinations (seeing things that aren’t there); mood, behavior or memory/thinking (cognitive) changes; or imbalance. Regular smoking or vaping also could cause lung damage. The potential risks on cognition, mood and motivation (to exercise or participate in other activities, for example) are especially important for people with PD.
Cannabis also could interact with other medications you are taking. While interactions are largely unknown, adding cannabis to a complex regimen of Parkinson’s and other prescription medications could present a risk. It’s important to tell your Parkinson’s doctor what you are taking, so that they can alert you to possible interactions.
Why is cannabis research difficult?
Several factors limit the ability to perform research and interpret results:
- Regulations may deter investigators and participants.
The federal government classifies marijuana as Schedule I, which includes drugs that have no current acceptable medical use and a high potential for abuse. The Michael J. Fox Foundation supported legislation that eliminated barriers to conducting medical cannabis research. Funding restrictions also may limit research.
- Studies often have limitations.
Size, design, and lack of standardized formulations or dosing make it difficult to compare studies and draw conclusions. Many studies include small numbers of participants, so it’s unlikely the group represents the broad Parkinson’s population or that results apply to the majority. Few studies include a placebo group, which makes it difficult to determine how much benefit may truly be from cannabis and how much might be placebo effect. And studies that include questionnaires rely on individual report, which may involve bias or inaccuracies.
There also is a lack of standardization. Different studies use different formulations with different amounts of THC and CBD. This makes it challenging to understand what might be doing what (why one trial fails and another shows positive results, for example) as well as what type of cannabis may work best for an individual or specific symptom.
How can I talk to my doctor about cannabis?
If you are considering or taking cannabis, let your doctor know. They may be able to help you weigh the pros and cons, and they’ll have a complete picture of all your treatments (prescription or otherwise) in case there is a change in symptoms or possible drug interaction. They also can direct you to ongoing research studies, if of interest.
If you are thinking about cannabis, you may want to ask your doctor:
- What symptoms it may help
Be clear about what symptoms you hope to treat — anxiety, sleep, pain or others. (In general, cannabis seems more useful for non-motor than motor symptoms, but experiences vary.)
- Potential benefits and side effects
Consider your medications and symptoms. Might cannabis lower blood pressure and counteract the medication you take to raise blood pressure? Or could it worsen your symptoms, such as thinking changes or imbalance?
- Their recommendation
Some physicians are willing to incorporate cannabis into your treatment regimen; others are less comfortable. Be aware that, unfortunately, many doctors may not know details about the many available products or be able to recommend a specific product or dosing. If you wish to try medical marijuana, ask if they can help you with the process (see below) or if they can refer you to someone who can.
Try to be open, honest and willing to hear what your doctor says. Tell them you are looking at all treatment options and want to learn if and how cannabis might help. And if you are considering or taking specific products, share which. (Bring printed information or a picture of the label.)
How can I access cannabis?
As of April 2021, 36 states and the District of Columbia allow the use of medical cannabis. The authorized medical conditions, formulations, and patient and physician requirements are different in each state. Note that even if Parkinson’s is a condition for authorized use, there may be additional requirements, such as also having another diagnosed condition (severe pain, nausea or malnutrition, for example).
Under federal law, doctors cannot prescribe cannabis. But qualified doctors (those who have completed additional training and registration) can issue "certifications" that permit patients to get a license for medical cannabis. Many doctors choose not to pursue qualification and therefore are not able to issue certifications. (Some states maintain registries of qualified doctors that you can search online.)
With a license, you can visit a dispensary, which sells cannabis products. Licenses typically don’t specify dosing or product information, so you work with the dispensary for recommendations on what may work for you. (This often is a trial-and-error process.) As the same product may vary significantly from location to location, it’s best to stick with one dispensary.
In states that have legalized recreational cannabis, you don’t need a license for purchase. However, having a license may decrease costs and provide access to dispensaries that may be more familiar with your condition.
What else should I know?
Many doctors and researchers believe the marketing and hype of cannabis products is ahead of the science and evidence. Be wary. Many have watched videos of people with PD using marijuana and seeing all their symptoms disappear within seconds. There also are many internet stories about marijuana as an “all-natural” cure for Parkinson’s (as well as cancer and other conditions). In general, when social media provides a level of endorsement significantly out of proportion to what you hear from your doctor, it is probably too good to be true.
What research is ongoing?
Researchers continue to work on defining safety for cannabis in Parkinson’s. And several studies are looking at possible benefits on specific symptoms. For the most up-to-date clinical trial information, visit Fox Trial Finder.
Through a recent questionnaire in MJFF’s Fox Insight online study, nearly 1,900 people with Parkinson’s shared their experiences with cannabis. In general, most people reported benefits on sleep, anxiety and pain. But some also had side effects and nearly one-third reported not discussing use with their physician. Full results are expected later in 2021.
The Michael J. Fox Foundation also recently convened a workshop on this topic with field leaders and other Parkinson’s organizations. Participants examined opportunities and challenges, agreeing that much work remains to understand how patients and doctors are using and talking about these products; to build education and communication around cannabis and Parkinson’s; and to evaluate safety, potential benefits, side effects and drug interactions, as well as the optimal dosing and formulations.
The medical information contained in this article is for general information purposes only. The Michael J. Fox Foundation has a policy of refraining from advocating, endorsing or promoting any drug therapy, course of treatment, or specific company or institution. It is crucial that care and treatment decisions related to Parkinson's disease and any other medical condition be made in consultation with a physician or other qualified medical professional.