Guidance for the Parkinson’s Community on Medical Marijuana Treatments
Parkinson’s disease (PD) can be very challenging to cope with, causing a mixture of motor and non-motor symptoms that affect nearly every aspect of daily living. Although the medications that doctors prescribe can be helpful, there remain gaps in what the medications can treat. Understandably, people with PD are eager to find alternative methods to help their symptoms, leading many of these patients to look into whether other therapies such as medical marijuana, also known as medical cannabis, can be useful.
Cannabis and the brain
Cannabis is a genus of plant that when ingested by humans, can exert numerous effects on the brain and body. The cannabis plant, of course, did not evolve to be used by humans. Humans, however, are naturally curious about their environment, and discovered these effects nevertheless. In this regard, cannabis is no different from many other plants from which humans have extracted products, such as the foxglove plant from which digoxin, a medication for heart disease was derived, or the Taxus species of plants from which paclitaxel, a medication for certain cancers was derived.
With further scientific investigation, it was discovered that the effects of the cannabis plant occur through the binding of certain chemicals in cannabis to a system of receptors in the human brain, named the endocannabinoid system (ECS). Cannabis contains more than 60 of these chemicals.
The Endocannabinoid System
The endocannabinoid system (ECS) is composed of:
- receptors that are expressed throughout the nervous system
- ligands, which are natural chemicals manufactured in the body that bind to these receptors
Through this binding, the ECS regulates many functions including mood, pain, memory, and appetite. The name of this system is unfortunate, as it implies that it evolved with cannabis in mind. The reverse is true. First the ECS evolved in humans. Then scientists discovered that certain chemicals in the cannabis plant could mimic the naturally occurring chemicals that are meant to bind the receptors.
Marijuana and Public Health
Cannabis is a substance that can be abused – that is, taken for non-medical reasons in a manner that can be harmful. Cannabis can stimulate the reward system of the brain and cause a pleasurable “high”, which can then be sought after by the user, leading to further use. Cannabis can change how a person perceives their surroundings and affect memory, reaction time, judgement, and ability to learn. Despite this, it was noted anecdotally by users that certain medical problems, such as chronic pain for example, were improved with marijuana. This led to efforts to create medical marijuana – purified chemicals from the cannabis plant, used at the doses that produce the desired result without harmful effects.
THC and CBD
The two primary chemicals that are isolated from the cannabis plant are Delta-9-tetrahydrocannibinol (THC) and Cannabidiol (CBD). THC exerts the mind-altering effects that recreational marijuana is known for, whereas CBD does not. For the most part, medical marijuana consists of purified combinations of these two chemicals in varying ratios. The combination can be dispensed as a liquid, pill or nasal spray. Both THC and CBD interact with the ECS.
Read more about CBD and Parkinson’s disease
Medical Marijuana and Parkinson’s disease
Since CBD and THC are chemicals that occur naturally in a plant, they were by definition not designed to combat any of the symptoms of PD. It is unreasonable therefore to expect that they will be a solution to all that ails a person with Parkinson’s. More research needs to be done, but based on what is known about the biology of cannabis, one could hypothesize that THC and/or CBD may be helpful for aspects of PD such as tremor, stiffness, insomnia, dystonia, pain, dyskinesias or weight loss. However, clinical trials are needed to prove:
- Which of these specific symptoms are helped?
- What ratios of THC and CBD work for a particular symptom?
- What doses of THC and CBD work for a particular symptom?
Because the history and politics of marijuana trigger such strong emotions, it is understandable that the public has begun to think of THC and CBD as unique substances with their own rules. But they should not be viewed this way. They are chemicals found in plants that have effects on the human brain and body and may help humans cope with some difficult medical symptoms. And if they are used by humans to cope with a medical symptom, then they are medications. To that end, we need to treat THC and CBD as the medications that they are and subject them to the same standards that we do any medication. Clinical trials can help us understand what symptoms they treat and what doses are needed. A major limitation to performing clinical trials with medical marijuana is that the federal government continues to consider marijuana an illegal substance and will not fund research involving marijuana. There are various efforts to try to change this, with the hope of opening up medical marijuana to further study.
Because marijuana remains federally illegal, doctors can’t write a prescription for it, but rather can write a letter to recommend marijuana. This letter is typically shown at a medical marijuana dispensary to receive marijuana.
One must also consider that just like any medication, medical marijuana can interact with other prescription medications such as those that cause sleepiness or thin the blood. In addition, medical marijuana can have side effects. And just like any medication, the side effects will vary depending on the person taking it. Elderly patients are typically more susceptible to side effects, for example. Some side effects that might occur include sleepiness, confusion, difficulty concentrating, apathy, mood changes, and gait imbalance. Therefore, before even considering medical marijuana, especially in the elderly, patients need to discuss how marijuana interacts with their other medications and weigh all the risks and benefits with their doctor.
Clinical Trials in Parkinson’s disease with CBD and THC
Several clinical trials have been conducted investigating the role of medical marijuana in the treatment of a variety of PD symptoms. Because the trials differ in many of their variables, it is hard to easily compare them to each other or draw any consistent clinical guidance from them. The trials vary in the type of medical marijuana used (e.g. CBD in various forms, cannabis extracts, and nabilone, a chemical analog of THC), the dosage used, and the study design (observational studies with surveys; open-label studies in which doctor and patient were both aware that the patient was receiving treatment and there was no control group; or blinded and placebo-controlled studies.) The trials were all conducted on a small number of patients – the largest was 38 – divided among those receiving treatment and those receiving placebo.
Most importantly, the trials also range in the symptom(s) being studied which include motor symptoms of PD and levodopa induced dyskinesias (LID), as well as various non-motor symptoms including sleep, cognition, anxiety, and pain. Results were varied, with some trials showing no effect and some trials showing improvement in certain outcome measures in the treated group. The bottom line, is that more data is needed, but currently, there is some data showing that medical marijuana may improve measures of quality of life, LID, pain, anxiety, and sleep.
As more data on the use of medical marijuana for PD is collected, we will know more. Even without more robust data, PD is typically one of the diseases for which a patient can obtain medical marijuana in the states in which it is available.
Medical Marijuana Availability
While not federally approved nationwide, in the United States, medical marijuana is available in some form in 47 states, based on individual state laws.
- In 24 states, marijuana is fully legal (medical and non-medical)
- In 14 states, marijuana is not fully legal, but medical marijuana is legal
- In 9 states, only medical marijuana products that consist of CBD/low THC are legal
- In 3 states, there are no medical marijuana provisions. Marijuana in any form remains illegal.
Even in the states that allow medical marijuana, there is wide variability in how easy it is to obtain it. A doctor’s recommendation is required, and it is distributed from specific dispensaries and not from a general pharmacy. Doctors often are required to take a special course before they are allowed to recommend medical marijuana. Many doctors have not taken this course which means that only a subset of doctors can prescribe marijuana.
Therefore, in some states, a person can purchase any product that he/she wants. In other states, a person needs to see a specific doctor (often not his/her own) to obtain medical marijuana. And in other states, a person can’t obtain medical marijuana at all.
Tips and take-aways
- Discuss the decision of whether to try medical marijuana with your physician. The discussion will include whether you have particular symptoms that may be amenable to treatment with medical marijuana, whether you take any medications that could interact with medical marijuana, and whether you might be at lower or higher risk for adverse side effects from medical marijuana.
- If you try medical marijuana, assess the positive benefits and the side effects just like you would any medication that you try and report back to your physician.
- Keep on the lookout for additional clinical trials to help assess whether medical marijuana is useful for specific PD symptoms.