Don’t Ask, Don’t Tell: Cannabis Use in Patients Diagnosed With Parkinson Disease

Abstract

Background: Public opinion and policy changes are redefining the use of cannabis. Most recently cannabis use is on the rise in the aging population as it is being introduced as a complementary health practice for neurologic disorders, one of which is Parkinson disease (PD). While there are advances in the treatment for PD, there is no prevention or cure. What remains is symptom treatment. Although some individuals diagnosed with PD are readily using cannabis to treat symptoms, there is limited evidence on usage and the health implications for healthcare practitioners.

Purpose: The purpose of this study was to determine use, attitudes, and experiences with cannabis among individuals diagnosed with PD.

Methods: A mixed-methods, anonymous, Web-based survey was administered through The Parkinson Alliance website and completed by 504 participants. Data gathering was performed using a Qualtrics survey and included both qualitative and quantitative data. 

Results: Most participants (almost 80%) who were using cannabis for PD stated that they received at least some symptom relief after using cannabis. However, only approximately 33% acknowledged that they felt very supported by their primary care physician or neurologist when using cannabis. Some participants chose not to use cannabis for PD symptomology, but some who were using cannabis noted:

1. when all else fails, try cannabis, 
2. multiple uses for cannabis, and
3. healthcare practitioners may not be the best support system. 

Conclusions: Results from this study may inform healthcare practitioners about alternative or complementary health practices for individuals diagnosed with PD. Identifying key factors about cannabis use and the experiences of those who use cannabis may assist healthcare practitioners in discussing cannabis with patients, which may lead patients to become more open about their usage. More dialogue about cannabis may, in turn, lead to more evidential advances. 

Introduction

Public opinion and policy changes are redefining the use of cannabis. The number of individuals using cannabis has risen to more than 200 million people aged 15 to 64 years worldwide.¹ That is more than 4% of the global population, and use has increased from previous years. While the reason behind the increase is not completely known, various physical, psychological, and emotional effects have been ascribed to the use of cannabis. 

Generally speaking, cannabis is perceived as an anxiolytic, antidepressant, antiemetic, anti-inflammatory, antispasmodic, pain modulator, and sedative, thereby piquing public interest in utilizing cannabis for symptom management.^2-5 Most recently cannabis use is increasing in the aging population as it has been introduced as an adjunctive treatment for neurologic disorders, one of which is Parkinson disease.^6,7 While there are advances in the treatment for Parkinson disease, there is no definitive cause, prevention, or cure. What remains is symptom treatment. Although some individuals diagnosed with PD are readily using cannabis to treat symptoms, there is limited research on the reasons for the use and the implications for health. This study delves into details about the users, their use, and their experiences with cannabis.

Literature Review

A search of the literature was conducted using terms relevant to the study topic. The etiology and progression of PD were explored, followed by extensive research on current use of cannabis. The use of cannabis for medical purposes, specifically neurological conditions, was examined broadly to gain a better understanding of the efficacy and risks of cannabis. The databases used to complete the literature review included the Cumulative Index to Nursing and Allied Health Literature (CINAHL) and PubMed. The search was limited to peer-reviewed, full-text articles and publications in English. With each database, the publication date was initially set to pull only articles from a maximum of 5 years ago, but this was advanced to 10 years due to the scarcity of information.

The keywords searched were: Parkinson’s disease, cognitive impairment, marijuana, cannabis, health benefits, and health risks. Each keyword was investigated individually and then clustered together. The first database searched was CINAHL. From the results, 110 articles were reviewed, and a dozen articles truly aligned with the research topic of interest. 

The next database searched was PubMed. Searching Parkinson’s yielded 137,000 articles; Parkinson’s and cognitive impairment uncovered 8,669 articles; and marijuana and cannabis displayed 34,422 articles. The keywords were grouped to narrow the focus. This was done to gain a better understanding of both the negative and positive effects of cannabis on the body. Based on the search results, the time frame was adjusted to include the past 10 years. Under this altered criterion, there were 10 articles that provided the initial research needed for the study. In addition, the references listed in the articles yielded additional useful articles. 

In reviewing the literature about PD and cannabis, there was a lot of information about both topics independently. When the 2 topics were combined, information became sparse. Concrete conclusions of efficacy could not be made. Most studies were based on self-reporting and individual judgment, which makes it difficult to ascertain if cannabis is safe and effective to use for PD. Some subjective studies described positive outcomes from the use of cannabis in the short term, but randomized controlled trials did not significantly support these findings. In this literature review, a noticeable amount of literature detailed the positive aspects of cannabis for PD, but the same amount of literature described the adverse effects of the drug.

Parkinson Disease

Parkinson disease is a progressive neurodegenerative disorder whose prevalence has steadily increased over the past 3 decades.⁸ Although it is associated with a significant decline in neurological function, it is typically characterized by motor and nonmotor disabilities. Motor impairments, which are the hallmark signs of PD, include bradykinesia (slow movements), resting tremors, postural instability, and rigidity.^7,9-14 Nonmotor manifestations include cognitive impairment, anxiety, insomnia, fatigue, pain, and depression.^7,9,10,12,15 

The etiology of PD is very complicated and is known to affect each person differently. The main pathophysiology includes the progressive loss of dopaminergic neurons within the substantia nigra.^13,16,17 Dopamine is the primary neurotransmitter affected by PD. Motor deficits are typically evident after 80% of dopamine and 50% of nigral neurons are lost.¹⁸ Since this loss occurs gradually, patients with PD may not experience physical symptoms until the disease has progressed. 

Pharmacological Treatment for Parkinson Disease

Prescription drug therapy is the main treatment for PD. Drug therapy for PD is used to help alleviate the hallmark motor symptoms of the condition. Typically, drug therapy focuses on a dopamine-replacement strategy, with the most common drug used being carbidopa/levodopa.¹⁹ This medication works by converting levodopa (the precursor to dopamine) to dopamine, resulting in more dopamine inside the brain.²⁰ 

Some of the other commonly used pharmacological classes of medications for treatment include dopamine agonists and monoamine oxidase amine-B (MAO-B) inhibitors.²¹ Dopamine agonists work similarly to dopamine. Since PD is characterized by a loss of dopaminergic neurons, these medications help to balance out the loss by acting as the neurotransmitter. Monoamine oxidase amine-B inhibitors work by inactivating the enzyme responsible for the inactivation of dopamine, once again helping with the loss of dopaminergic neurons.¹⁹ 

The efficacy of pharmacological interventions, particularly levodopa, tends to diminish or deactivate. During this time, individuals experience a recurrence in their symptoms, both motor and nonmotor.^22,23 There is no standardized way to prevent the decreasing effect of PD medications. Some solutions include changing the medication or dose or adding another medication to help the original medication work efficiently.^22,23

Current pharmacological measures are also used to treat common nonmotor symptoms, such as pain and anxiety. For these symptoms, opioids and benzodiazepines are the drug classes used.⁶ Although these medications are effective in treating general symptoms, they also have many adverse effects. 

Opioids have side effects inclusive of dependence, constipation, confusion, and weakness.^6,24 Benzodiazepines may be ordered for anxiety and antipsychotics used for behavior disturbances. Benzodiazepines may create sedation, dependency, and a risk of falls, while antipsychotics produce symptoms of metabolic syndrome or impaired voluntary movement (dyskinesis).^6,25 Antidepressant medications may be used for mood disorders, which may have side effects of drowsiness and a risk for falls.^6,26

Although these medications may be helpful in treating PD on a symptomatic basis, adverse effects must be taken into consideration, especially as PD usually applies to higher risk individuals, such as older adults. Additionally, several medications taken for a variety of symptoms create a polypharmacy effect where multiple drug interactions need to be managed. Complementary treatments, such as cannabis, may be sought to alleviate symptoms and diminish the possibility of numerous side effects.^6,15 

Cannabis

Cannabis is a flowering plant, which in its dried form is more commonly known as marijuana.²⁷ “Flavonoids, cannabinol, terpenoids, and cannabinoids are some of the bioactive molecules” that determine the traits of cannabis.²⁷ Of the cannabinoids, the most familiar are delta-9-tetrahydrocannabinol (THC), which is particularly identified as having a psychoactive component, and cannabidiol (CBD), which most know as having an anti-inflammatory factor.^9,27,28 The brain contains many cannabinoid receptors, in the endocannabinoid system. These receptors are highly expressed in areas of the brain where cognition, anxiety, behavioral impulse, pain, and anxiety are controlled.²⁹ These receptors have an antinociceptive, or blocking effect, in controlling perception of pain.²⁹ These cannabis products come in many forms that may be administered in multiple doses and routes. 

Dopamine and Cannabis Use

Dopamine is important in control of voluntary movement. Dopamine’s neurotransmission regulates the corticostriatal pathway, which is essential for voluntary movement.^2,30 A loss of dopaminergic neurons causes an imbalance between the direct and indirect pathways to control voluntary movement.¹¹ This imbalance is the foundation for movement disorders, such as in PD where the depletion of dopamine creates a slowing of movement (bradykinesia). A reduction of dopamine is attributed to the development of PD symptoms.

In the literature, there were various findings connecting dopamine and the use of cannabis. Using positron emission tomography (PET), Calakos et al³¹ found that participants who smoked cannabis while being scanned demonstrated induced dopamine responses. Hunt et al³² noted that cannabis indirectly decreases the reuptake of dopamine. However, in a meta-analysis of neuro-imaging studies by Kamp et al,³³ there was no significant difference in dopamine when using cannabis. 

Positive Effect of Cannabis

Generally cannabis is perceived as an anxiolytic, antidepressant, antiemetic, anti-inflammatory, antispasmodic, pain modulator, and sedative, thereby attracting public interest in utilizing cannabis for symptom management.^2-5 Cannabis produces a sedative-like feeling that some consider desirable for sleep.^{2-4,6,9,28,34,35} Cannabis is shown to have positive effects on anxiety and depression.^4,6,9,28,35 Cannabis also is noted to control nausea, pain, and spasticity.^5,6,9,28,35 Since cannabis products vary and have different ingredients, the effects of cannabis may vary which can alter an individual’s experience.

Negative Effect of Cannabis

Cannabis use has been associated with cognitive impairments, motor skill deficits, verbal disabilities, and mood disorders such as anxiety and depression.^2,5,6,30,36 Drug interactions between cannabis and prescription or even nonprescription medications have been reported as side effects; this is often seen in individuals using multiple drugs to treat comorbidities.^3,5 Adverse effects such as weakness, mood changes, hallucination, dizziness, fatigue, and anxiety have been reported.^4,6,9 Impaired motor coordination, slowed reaction time, anxiety, and impaired judgment were also described as undesirable outcomes.² Depending upon the product and dose they use, individuals may be exposed to these or other unanticipated adverse effects. 

Additional negative effects of cannabis include cannabis use disorder, which is described as an inclination to use larger amounts of cannabis more frequently, and cannabis withdrawal syndrome, symptoms of which include diaphoresis, pyrexia, headaches, irritability, tremors, and poor sleep quality.^2,6,7,27 Age-related changes or conditions of the kidney or liver exacerbate the toxic effects of cannabis in the body as it is metabolized and excreted by the liver and kidneys.^3,5,6,37 Other negative effects include new substance use disorder,⁵ cognitive impairment, dizziness, anxiety, and decreased motor skills.^7,27 Additionally, hallucinations, cardiovascular events, and loss of cognitive abilities have also been reported.³⁸ These negative effects have been primarily related to the THC components. Some individuals who use cannabis are also concerned about the judgment and stigma attached to cannabis use, despite the legality in multiple jurisdictions.^6,28,34,38 

Dose Is Not the Same as Potency

When identifying dosage for CBD or THC, a unit of weight is most often used (eg, 3 mg, 4 mg, etc). Potency is expressed in percentages.³⁹ If a cannabis flower weighs 10 mg on the scale and has a 10% potency of THC, the dose of THC would be 1 mg, which is a very low dose. Products identifying as CBD usually have a 0.3% or less potency of THC. It is also important to mention that synthetic versions of cannabinoids usually have more of a consistent prescriptive potency as compared to naturally occurring cannabinoids where potency can be variable.

THC/CBD Products

For CBD, some products can include gummies, capsules, pills, or oil. For THC, some recognizable products are concentrates, edibles, tinctures, smoke, or vape. Depending on the product, dosage recommendations come in a variety of ranges. The average potency of THC is approximately 20%, but concentrates can reach 80% or higher potency.⁴⁰ Additionally, CBD and THC products are sold independently or in combination. An individual needs to know the content of the product to estimate the benefits or adverse effects.

CBD Dose and Relationship Response

Using a higher dose does not always mean a better outcome. Studies reveal an inverted U-shaped dose-response curve in relation to anxiolytic effect.^39,41,42 After administering cannabidiol to healthy adults in increasing doses, researchers noted that neither the lower nor the higher dose of CBD had a more significant effect on anxiety than the intermediate dose—demonstrating that more is not always better. 

American Academy of Neurology

Based on the lack of medical research regarding cannabis and neurologic disorders, the American Academy of Neurology (AAN) does not support the use of cannabis products as treatment options for most neurologic disorders.⁴³ This includes not supporting cannabis for PD. Safety concerns regarding the efficacy of cannabis, the potentially toxic interactions from certain compounds in the product, and the regulation of quality has led the AAN to decline to support overall usage.⁴⁴

Purpose

The purpose of this study was to determine use, attitudes, and experiences with cannabis among individuals diagnosed with Parkinson disease.

Methods

A mixed-methods approach was used for this research. A Web-based survey focusing on a purposive sample was offered through The Parkinson Alliance and completed by roughly 500 participants with PD. The Parkinson Alliance was a nonprofit organization dedicated to supporting Parkinson patients and their families. Since its founding in 1999, it supported the development of new therapies and improved the quality of life for those living with the disease through patient-centered research and resources.⁴⁰ The Parkinson Alliance strongly believed that the patient’s voice is essential when evaluating new treatments and healthcare in general. In 2022, The Parkinson Alliance decided to close operations and transfer the production, execution, and ownership of the Parkinson’s Unity Walk to The Michael J. Fox Foundation for Parkinson’s Research.⁴⁰

Procedure

Between September 2022 and October 2022, individuals diagnosed with PD were invited to participate in an anonymous online survey study regarding the use of cannabis. The sampling strategy focused on extracting important data from a variety of individuals diagnosed with PD.

The study was posted on The Parkinson Alliance website. Those diagnosed with PD completed the approximately 75-item survey, which collected data on demographics, cannabis use, perceived benefits, adverse effects, and expectations of healthcare providers. In total, 508 individuals diagnosed with PD completed the survey and shared their experiences with cannabis. Four participants did not meet the inclusion criteria of being 18 years or more or having a diagnosis for PD and were subsequently excluded from the survey. After data cleansing, 504 participants remained.

Inclusion criteria included individuals aged 18 years or more who are diagnosed with PD and have the capacity to understand the survey. Exclusion criteria included individuals aged less than 18 years, individuals not diagnosed with PD, and individuals diagnosed with PD but with limited capacity to make decisions or understand the survey. 

Informed consent was obtained from each participant as noted at the beginning of the survey, where individuals were informed that the survey was voluntary and that they did not have to complete the survey. Completion of the survey implied consent. The study was approved by the Institutional Review Board of The College of New Jersey in Ewing, New Jersey.

Data gathering was performed on a Qualtrics survey and included both qualitative and quantitative data. The Qualtrics platform provided a secure environment regarding privacy and protection of data. Survey data was automatically de-identified before any analysis was performed. Responses to the survey were self-reported, and no responses were verified by any other means.

• The final survey consisted of 75 open- or close-ended questions, with participants skipping some questions based on the previous answers. Time required to complete the questionnaire was approximately 20 to 30 minutes. Demographic details of participants were analyzed using descriptive statistics. 

Results

Participants of this study were an average age of 69 years, with the youngest participant aged 39 years and the oldest participant aged 101 years. The average age at which participants reported being diagnosed with PD was 60 years, with the youngest age being 31 and the eldest 82. Approximately half identified as male, and half identified as female. One percent preferred not to identify a gender. Participants’ races consisted of White, Hispanic/Latinx, Asian/Asian American, Native American/American Indian/Alaska Native, and Black, and less than 2% in every other race.

The majority of the participants were from California, followed by Florida, and then New Jersey. However, 41 states were represented by the participants, and of those, 19 states had legalized cannabis at the time of the survey. Thirty-two participants were from outside the United States from countries such as Australia, Italy, Canada, the United Kingdom, Denmark, Germany, Spain, and Ireland. Eighty-seven percent of the participants were from a place where cannabis was legalized. See Table 1.

A number of participants reported using cannabis recreationally prior to using it for PD. The average age for the recreational use was 27 years. Around half of the participants in this study said they did not use cannabis for PD and had never used it in the past. Interestingly, of the participants using cannabis for PD symptomology, only 55 participants were using cannabis prior to using it for PD. Almost 200 (190) individuals at the very least tried cannabis for symptom relief after being diagnosed with PD. There was no definitive pattern of when the participants started to use cannabis for their PD symptoms; some started immediately after being diagnosed with PD, while others waited years before they began using cannabis. 

The average age at which participants started using cannabis for the treatment of PD was 64 years. Some participants who began using cannabis said they stopped because they did not like the side effects, could not afford it, it was illegal in their state, or for other reasons such as it didn’t work for them, they were unable to find a regular supply, or their friends, family, or physician were not in support of using cannabis. The majority of the participants who were still using cannabis for symptom treatment have been using it for 1 to 5 years. Participants’ descriptions of their use frequency ranged from very frequently to very seldomly. Those who use cannabis primarily articulate that they get a little symptom relief. Symptom relief was mostly related to relaxation, sleep, pain, anxiety, and emotional coping. See Tables 2 and 4.

Of the participants who currently use cannabis, approximately 23% have not informed their primary care practitioner or neurologist about their use of cannabis. Most noted that their PCP and/or neurologist were not very supportive and cited several reasons for not sharing the information with the physicians. See Table 5.

Table 1: Participant Demographics

Table 2: Use of Cannabis

Table 3: Types of Cannabis Used

Table 4: Cannabis Used for Symptoms

Table 5: Participants Who Use Cannabis and Informed Physician of Use

What the Participants Said

Participants relayed their thoughts on why they use cannabis, adverse effects, and impressions of healthcare practitioners. See Tables 5, 6, and 7. Qualitative responses from the participants included using cannabis for pain, anxiety, sleep, mood, dyskinesia, and tremors. Some mentioned that nothing else seemed to be working, so why not try cannabis. While others stated their aversion to pharmaceuticals and preference for herbals. Several participants identified friends, family, or physicians who suggested trying cannabis for symptom relief.

Negative characteristics were also associated with the use of cannabis. Adverse effects of confusion, anxiety, hallucinations, dizziness, and unsteadiness were identified. When asked if they had discussed use of cannabis with their physician, those who had not discussed it gave reasons about judgement, stigma, legalities, and physicians not needing to know. 

Table 6: Why Participants Chose to Use Cannabis for PD

Table 7: Adverse Effects

Table 8: Interactions With Physicians

Discussion

Lessons learned from this research included some key items. When all else failed, individuals were more likely to try complementary or alternative methods. Symptom management is key to treating PD. As prescribed medications became ineffective, participants were more open to try cannabis. 

Individuals had a concern about polypharmacy and adverse reactions. Symptom management often included more than 1 medication, and side effects were noted with each of these medications. Some participants preferred to take fewer prescribed medications so as to not have competing side effects. 

Public opinion mattered to many participants. How the participants perceived they will be viewed directed their actions. This was evident when some participants were not informing their PCP or neurologists about their cannabis use for fear of being labeled as a drug addict or disreputable. How healthcare practitioners approached the subject of cannabis use made a significant impact. If the healthcare practitioner gave an unapproachable impression, participants reported they may not relate important details about their health, which may  be to the detriment of a patient. 

Since more people, especially more elderly people, are trying cannabis, it is imperative that more research be done on the effects of the drug and how it affects different populations. Additionally, cannabis is becoming legal in more states. There needs to be a dialogue about cultural acceptance, cost, and amelioration of symptoms. At this time, participants report taking a variety of types and dosages without medical oversight. Healthcare-practitioner guidance is needed for the individuals who have a neurological diagnosis and are using alternate or complementary treatment.

Limitations

There were some limitations in this study. The most important limitation was the self-reported survey. There was no supervision over the responses as the participants were answering the questions. Each participant read the questions individually and answered to the best of their ability. There was a statement to contact the researcher if there were any questions, though no participant did so.

Dosages, usage, and potency of cannabis were typically different for participants. It was unknown whether cannabis alone was causing the positive results or adverse effects reported by the participants or if the outcomes were caused in conjunction with more traditional medications. Additionally, no comparison was done considering other medications or comorbidities.

Lastly, this study used purposive sampling. Data was gathered through 1 online survey through 1 website. Different results may have been produced if the sample size were larger or the survey went out to multiple websites.

Conclusion

In summary, some individuals diagnosed with PD self-reported improvement in some symptomology with cannabis use, while others reported no change or worsening of symptoms . There was insufficient agreement on the efficacy and effects of the drug. Until further studies are done and long-term results are known, we cannot know the full effect of cannabis on PD.