Although Huntington’s and Parkinson’s diseases come from different origins and are usually discovered in different populations, both affect the area of the brain that controls movement (see our articles on ALS and Alzheimer’s). Huntingon’s shows up in a younger population than Parkinson’s and almost always has origins that are genetic in nature, affecting cognition, mood, and movement. Parkinson’s tends to affect people later in life, over the age of fifty and symptoms include tremors, rigidity, slowed movement, and impaired coordination and balance. The current modern day evidence seems to suggest that cannabinoid treatment can be extremely effective in helping in conditions of this type, as they have the ability to suppress the excitotoxicity, glial activation (a source of centralized pain), and oxidative injury that can cause neural degeneration. Cannabinoids assist on multiple levels as neuroprotectants that potentially slow the progression of disease, while also helping with a variety of parkinson's symptoms. 
Scientists in 2008 and later in 2014 found that CBD had shown the ability to recover memory deficits induced by brain iron accumulation, which is found to be involved in the pathogenesis of a number of neurological diseases.  It can also improve the function of mitochondria in cells and activate the clearance of debris, further encouraging neuron health.  Also, cannabidiol (CBD) could help people experiencing neurodegenerative-related psychosis. 
Tetrahydrocannabinol (THC) has also been found to assist in neurodegenerative diseases by protecting against damage caused by free radicals and activating the formation of new mitochondria.  As for helping with symptoms, products with a varying ratios of CBD to THC have been discovered to create significant improvements in tremors, bradykinesia, motor impairments, pain, and sleep.    A study from 2014 on people with Parkinson’s had scientists find benefits in well-being and quality of life scores in general after just one week of using CBD. 
However, one study from 1991 utilizing cannabidiol with Huntington’s yielded less than satisfactory results,  twenty years later GW Pharmaceuticals, covered the limitations of previous research done, started with preclinical trials utilizing their product, Sativex, which is a 1:1 CBD:THC oral spray that’s been approved in over thirty countries world-wide for the spasticity associated with multiple sclerosis.  Initial results didn’t reveal any statistically significant improvement in cognitive or motor deficits, but the drug was well tolerated and studies using higher doses are still being carried out. In a study from 2015, cannabigerol (CBG) also showed promise as a neuroprotectant with a variety of beneficial actions on brain health. 
The information contained in this article is not a substitute for medical advice. Prior to making changes to your treatment plan, consult with your healthcare professional. It is suggested people work with a doctor who is experienced in recommending CBD or medical marijuana so the delivery method and dosage can be adjusted and fine tuned based on the individual, including managing side effects. At the same time, those who are highly aware and educated, can become their own highly informed health consultants. Depending on the country in which you reside, will depend on the availability of cannabidiol and cannabis products.
Always begin with a micro dose to test for sensitivity and titrate up as needed within the dosing range by body weight until symptoms subside. People should be cautious about titrating up slowly to a target standard to macro dosing range to ensure minimal psychoactive effects. Strains that are high in the terpene myrcene have a more relaxing effect, and strains high in THCV are indicated for their potential neuroprotective properties.
While that being said, cannabis products created with broad-leaf, indica-dominant varieties that are higher in THC can be of assistance for the treatment of sleep issues (see our article on cannabinoid support for sleep disorders) or create a sedating and calming effect. A maximum range of 5-10 mg of THC per dose is suggested. Avoid using items that contain sativa-dominant strains as they can promote hyperactivity and dissociation. Smoked or vaporized is typically the go-to for immediate relief of symptoms, or a boost in dosage, and this method can also be of value for sleep issues. Tinctures of sublingual sprays can take effect rapidly and last longer than inhaled products. For reasons of safety, vaporized or smoked products aren’t generally used for patients with advanced cognitive symptoms.
When higher doses are needed, a lot of people will use a concentrated form of cannabis oil, taken orally, or in a capsule form, or by adding to food (nut butters can also work). The most potent, purest concentrates are created using CO2 extraction.
The Cannabis Health Index is a scoring system based on the best available evidence found in the medical literature to date on medicinal cannabis, not just CBD. Based on the best available data, Huntington’s disease scored in the possible-to-probable range of efficacy, and Parkinson’s scored the same.
A study from 2007 showed that cannabinoids can produce a neuroprotective effect against the progressive degeneration of nigrostriatal dopaminergic neurons occurring in Parkinson’s. Data analyzed from 2009, suggested that CBD may be an effective, well-tolerated, safe compound for psychosis in neurodegenerative disorders,  and in a 2011 study on THCV researchers concluded that it contained “a promising pharmacological profile for delaying disease progression and also for ameliorating parkinsonian symptoms.” 
Cannabinoid-2 (CB2) receptor up-regulation has been discovered in many neurodegenerative disorders including Parkinson’s and Huntington’s, which supports the beneficial effects found for CB2 receptor agonists in both disorders. The current studies published in the medical literature, thus far, supports cannabinoids’ antioxidant properties and/or capacity for activating CB2 receptors as promising therapeutic agents in treating both disorders, and as such, deserves prompt clinical evaluation.  
In a study from 2018 on utilizing CBD for parkinson's disease, researchers concluded, “the beneficial neuroprotective profile of CBD added to the preliminary results described here are encouraging." 
An analysis of the research in 2020, had a science team analyze the current evidence finding that, “six preclinical studies showed neuroprotective effects, while three targeted the antidyskinetic effects of CBD. Three human studies have tested CBD in patients with PD (Parkinson’s disease): an open-label study, a case series, and a randomized controlled trial. These studies reported therapeutic effects of CBD on non-motor symptoms.” 
Another 2020 study involving 24 patients with Parkinson’s disease, discovered statistically significant differences in those receiving CBD treatment. The study showed that a dose of 300 mg significantly decreased anxiety and tremors when faced with an anxiety inducing situation such as speaking in public. 
The above study found that a single dose of CBD could assist with decreasing both tremor strength, and anxiety, in Parkinson's sufferers experiencing situations known to induce anxiety, which was public speaking, in this case.
In a study involving 1348 participants with Parkinson’s; those using medicinal marijuana experienced;
Researchers concluded that many people with Parkinson’s disease consider using medicinal marijuana a viable therapeutic option. They encouraged that both efficacy, long term safety, and the routes of administration should be investigated in further clinical trials. 
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