CBD and Parkinson’s Disease
Almost fifty percent of my patients inquire about medical marijuana for their Parkinson’s Disease at some point during the course of their condition. Marijuana, also known as Cannabis, is composed of over 400 different compounds. There are also different species of Cannabis, including C. sativa, C. indica and C. ruderalis. The percentages of these compounds vary from species to species. The cannabidiol (CBC) and tetrahydrocannabidiol (THC) are the two better research substances that make up the bulk of the plant compounds. THS is observed to be responsible for the psychoactive properties of marijuana, while CBD is used for the treatment of neuropathic pain and is devoid of psychodelic capabilities.
While pain can be caused by Parkinson’s disease and have a significant and debilitating impact on the quality of life most of my patients do not seek marijuana for its analgesic effects. Instead, recent animal research demonstrates neuroprotective effects of CBD. Can CBD interfere with progression of Parkinson’s and/or impact the motor symptoms of this condition? To answer this question we will first review the possible mechanisms of action of CBD and the preclinical data. Then we will zero in on the clinical trials.
Mechanism of Action of CBD
Cannabidiol (CBD) binds to several receptors including cannabinoid type 1 (CB1), CB2, TRPV1, PPARy and several others. These receptors are distributed throughout multiple systems in the body. CB1 is found within the nervous system, including hippocampus (responsible for memory) and basal ganglia. While the research is focusing on CB1 because of its direct connection with the nervous system, it is possible that the benefit is derived through the modification of the immune response via CB2. CB2 is found primarily on the cell of the immune system, but is also found on the nerves of the enteric/ gastrointestinal nervous system. Thus, CB2 could theoretically modify the gut brain interaction and influence the composition of the gut microflora.
Overall, cannabidiol exerts anti-inflammatory, antioxidant, neuroprotective and anti-convulsant effects on the brain.
Preclinical Studies on Cannabidiol (CBD)
Preclinical studies include animal research and studies conducted in a test tube. In the test tube, nervous tissue is subjected to Parkinson’s disease inducing toxins and is then bathed with the test substance; in the case the cannabidiol. Here a brief summary of the some of the research:
- Animals are injected with Parkinson’s disease inducing toxin (6-OHDA) and are subsequently given CBD for 6 weeks. The cannabidiol increases activity of antioxidant enzymes, such as superoxide dismutase, and prevents the depletion of dopamine.
- Chronic exposure to CBD increases mitochondrial activity within the animal brains
- Cell survive longer when they are exposed to cannabidiol, demonstrating protection against MPTP induced cell death
In the last 15 years or so there have been several attempts to evaluate the effects of cannabidiol (CBD) on Parkinson’s disease.
- Pilot study: Cannabidiol (CBD) was provided to patients with Parkinson’s disease (PD) with psychotic symptoms for 4 weeks. There are no side effects or aggravations of the motor symptoms. The psychotic symptoms improve.
- Case series: Four patients are given CBD for 6 weeks. There is no improvement in the motor symptoms, but the quality of life does improve.
- Double blind exploration study: Twenty one patients with PD are divided into three intervention groups: placebo, 75 mg/d of CBD and 300 mg/d of CBD. The treatments are provided for 6 weeks. There is no significant change in the UPDRS score, a validated assessment of motor symptoms or brain-derived neurotrophic factor (BDNF). BDNF promotes regeneration of neurons and their components. However, there is a statistically significant improvement in the quality of life (assessed via PDQ-39) in the group taking 300 mg of CBD daily.
- Open-label observation study: Smoking cannabis for 30 minutes results in improvements in tremor, rigidity and bradykinesia.
We can see from the clinical trials that patients with Parkinson’s disease notice improvement in their quality of life. This may be due to CBD’s antidepressant, antipsychotic and/or anxiolytic effect. It is of course disappointing to see a lack of change in the motor symptoms or a delay in progression with respect to the CBD treatments. Perhaps there are additional compounds within Cannabis that will prove to be more effective for the movement component, or maybe the studies or the dose where not of appropriate duration or magnitude. Further research is needed to explore the full range of effects of CBD. From a safety perspective, patients using CBD can experience diarrhea, changes in appetite and fatigue. However, CBD does not interfere with cognitive processes (in patients with Parkinson’s disease), heart rate or blood pressure and does not trigger dyskinesia’s.
I believe each patient should discuss the benefits of CBD oil with their healthcare provider; neurologist, naturopathic doctor and/or family doctor, to arrive at a decision that is right for them.
- Peres F. Cannabidiol as a promising strategy to treat and prevent movement disorders? Frontiers in Pharmacology. 2018; 9: 482
- Chagas M. Effects of cannabidiol in the treatment of patients with Parkinson’s disease: an exploratory double-blind trial. Journal of Psychopharmacology. 2014.
- Lotan I. Cannabis (medical marijuana) treatment for motor and non-motor symptoms of Parkinson’s disease: an open-label observational study. Clinical neuropharmacology.2014; 37(2): 41-44
- Mouhamed Y. Therapeutic potential of medical marijuana: an educational primer for health care professionals. Drug, Healthcare and Patient Safety. 2018; 10: 45-66