Parkinson's disease (PD) is a neurodegenerative disease caused by the loss of dopamine-producing brain cells. Dopamine cells help control movement and also influence mood. Many individuals living with Parkinson's experience tremors, stiffness, or slowness of movement, and they may have depression or anxiety. The symptoms of the disease can also cause pain. The condition is both chronic and progressive.
There is still no cure for PD, but symptoms can be managed with surgery or medications that mimic or increase dopamine. Some of these medications can cause unpleasant short term-side effects, however, such as dizziness, nausea, or even compulsive behaviors. Unfortunately, the benefits offered by these medicines can wane or become unstable over time.
Emerging research suggests that CBD may offer therapeutic benefits for those living with Parkinson's.
What the research says
CBD has been shown to have anti-inflammatory, neuroprotective, and antioxidative effects in studies involving animal and human subjects. Both oxidative stress and inflammation play a role in Parkinson's and all movement disorders to some extent. CBD has also been shown to have anti-anxiety properties, which helps patients who experience anxiety or depression and increased tremors caused by anxiety.
Most of the human studies that have evaluated CBD as a treatment for PD have focused on its potential to help with non-motor symptoms, such as psychotic symptoms, well-being, and sleep disorders. But a 2020 study published in the “Journal of Psychopharmacology” shows that CBD can reduce anxiety in PD patients, and consequently, the intensity of anxiety-related tremors. There is also research in animal models indicating that CBD may help with the management of motor symptoms.
One 2018 review of existing research published in Frontiers in Pharmacology on CBD for Parkinson's disease suggests that CBD may play more of a preventive role in the illness rather than a therapeutic one.
A 2014 study on human participants published in the “Journal of Psychopharmacology” indicated that CBD might improve the quality of life of PD patients. The study's authors found improvements in functioning and well-being among patients treated with 300 milligrams of CBD daily over six weeks, and pointed to its anti-anxiety, antidepressant, and sedative properties as possibly explaining these improvements.
However, the study authors failed to find a statistically significant benefit of CBD for motor symptoms, nor was there evidence that CBD provided neuroprotective benefits despite evidence of neuroprotection in animal models. The authors did acknowledge that the study used a small sample (21 patients in total) and that longer tracking may be required for neuroprotective benefits to become apparent.
A 2014 case report published in the “Journal of Clinical Pharmacy and Therapeutics” investigated CBD as a treatment for REM sleep behavior disorder in four Parkinson's disease patients. Three patients received 75 milligrams of CBD per day, and one received 300 milligrams daily. All four patients received CBD for six weeks.
Nightmares, agitation, and aggressive behavior were promptly and significantly reduced in the case of one man, and completely ceased in the other three cases over six weeks. However, after the treatment was interrupted, symptoms returned with the same frequency and intensity.
A 2008 pilot study, also published in the “Journal of Psychopharmacology”, evaluated the efficacy, tolerability, and safety of CBD on Parkinson's disease patients with psychotic symptoms. Psychosis affects almost one-third of PD patients in the latter stages of the illness. Four men and two women who had had psychosis for at least three months received pure CBD in varying doses (beginning with 150 milligrams per day) for four weeks in conjunction with their usual therapy.
The results showed that the CBD treatment significantly improved thinking disorders, and also significantly decreased sleep disturbances, hallucinations, and delusions. Although CBD did not affect motor function in a statistically significant way, patients seemed to show some improvement. Patients tolerated the CBD treatment well, without experiencing adverse effects.
In Reddit forums, patients living with PD discuss their experiences of using CBD as a treatment for symptoms associated with the condition.
One contributor noted that CBD seemed to improve motor function to some degree.
“We've been trying drops under the tongue for the last couple of weeks with my father to help him sleep at night. Not used consistently enough to see if it's helping yet, but my mother notices some reduction in his hand tremors.”
Another contributor found that CBD was more effective when teamed with THC.
“I don't use CBD for my tremors (they are very minor unless I'm in a lot of pain or stressed) but I use it for muscle rigidity and pain. I personally do not find CBD as effective as THC, but I do use both.”
An individual living with Parkinson's disease shared his observations on a forum maintained by Parkinson.org after using CBD (without THC) for a month.
“Over the course of the past month, I've lost some of the super benefits that I thought I was getting during the first week, but the fact remains that a noticeable level of improvement has persisted. I really need help with anxiety, agitation, anger issues, autonomic nerve deficiencies, and many other non-movement type things. I think and hope that the CBD oil is helping.”
What the experts say
Fernanda F. Peres is the leading author on a 2018 review of CBD as a treatment for Parkinson's disease and other movement disorders, published in “Frontiers in Pharmacology.”
Peres is convinced that CBD holds strong potential in the treatment of PD.
“We have data pointing to CBD's beneficial effects on non-motor symptoms. Using CBD in addition to antiparkinsonian medications is a future possibility, in my opinion.”
Peres points out that first-line medications for PD, such as carbidopa-levodopa, improve the motor symptoms, but can lead to significant adverse effects such as psychotic symptoms or involuntary movements.
CBD, on the other hand only causes mild side effects, such as fatigue or a dry mouth in some individuals. Although there is currently a lack of clinical evidence in human studies, Peres believes that earlier diagnoses of Parkinson's disease will enable the neuroprotective properties of CBD to work better.
She points to the studies performed on rodents that demonstrate the beneficial effects of CBD on treating or preventing motor abnormalities and emphasizes that the difference between the human and animal studies is that PD is diagnosed later in human participants, compared with animal models in which PD is induced.
“Considering the neuroprotective effects of CBD, it might not be beneficial after extensive neurodegeneration. We speculate that future improvements in PD diagnosis criteria will lead to earlier diagnosis and will expand CBD's benefits for PD patients. CBD is a molecule with multiple mechanisms of action, not all of them fully elucidated.”
While there is evidence that CBD may improve quality of life and sleep in Parkinson's disease patients, more research on human subjects is needed to understand if CBD may help prevent or decelerate neurodegeneration that is the hallmark of PD.
Major contributions from Dr. Adie Rae.