Neurodegenerative diseases (NDs) are characterized by a progressive loss of structure and function of nerve cells in the central and peripheral nervous systems. (Bhunia, 2022) The structural loss of neurons and synapses including demyelination and neuronal death causes a gradual loss of motor and/or cognitive skills that can manifest in one of many forms of neurodegenerative diseases. Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the two most common NDs, while the other forms include amyotrophic lateral sclerosis (ALS), Huntington’s disease, spinal muscular atrophy, motor neuron diseases, prion diseases, and spinocerebellar ataxia. (Bhunia, 2022)
In the United States, it is estimated that about 6.2 million people suffer from Alzheimer’s disease and nearly a million are living with Parkinson’s disease. (NIH, 2022) Although certain treatments have been seen to relieve some of the physical or mental symptoms associated with neurodegenerative diseases, slowing their progression or curing them is not currently possible. Additionally, the likelihood of developing a neurodegenerative disease increases dramatically with age. (NIH, 2022) In the next few decades, more people will likely be affected by a ND due to the rising life expectancy.
Since no real treatment has yet been discovered, and due to the likelihood that the number of people affected by neurodegenerative diseases across the globe will increase, looking for ways to cure or at least delay the progression of these diseases is extremely important. More recently, cannabinoids have been considered as a potential tool within the medical realm to treat NDs due to their neuroactive and strong antioxidant properties. (Bhunia, 2022) Persistent neuroinflammation and chronic oxidative stress play a crucial role in the progression of these diseases. Because of this, cannabis use may potentially be an effective tool in improving the lives of people with NDs. In fact, emerging preclinical research studies have demonstrated that CBD can exhibit neuroprotective effects due to its antioxidant and anti-inflammatory properties, thus offering the possibility of treating different neurodegenerative diseases.
In a review of 86 studies that examined cannabis’ role in treating Alzheimer’s in 2019, the researchers found that CBD and THC may each offer some protective effects against the harmful symptoms of this disease. Some research examined the effects of CBD on AD in vitro. In these studies, CBD activated the Peroxisome Proliferator-Activated Receptor-γ(P-PARγ) through the Wnt/β-catenin pathway. (Kim, 2019) As a result, PC12 neuronal cells, which are cells that synthesize, store, and release norepinephrine and dopamine, were protected from neurotoxicity and oxidation stress. There was also an increase in cell survival, reduced ROS production, and reduced lipid peroxidation. (Kim, 2019 & Wiatrak, 2020) In vivo studies of CBD on AD demonstrated that CBD stimulated neurogenesis of the hippocampus and in vivo studies using both THC and CBD suggested that using both cannabinoids was more effective overall than using either in isolation. (Kim, 2019) Overall, these results suggested that the CBD and THC components of cannabis may be useful in treating or even possibly preventing Alzheimer’s due to the suppression of the main causal factors of AD.
Recent studies have also shown the promising protective effects of cannabis among people suffering from Parkinson’s disease. PD arises as a result of a loss of dopaminergic neurons in the substantia nigra, resulting in the loss of control of voluntary movements, which can manifest in tremors, rigidity, and bradykinesia. (Patel, 2019) There are also non-motor symptoms associated with Parkinson’s, such as psychosis, cognitive impairment, depression, and anxiety. (Patel, 2019) Medical marijuana has been seen to improve both motor and non-motor functions. (Patel, 2019) Additionally, one study conducted on patients with Parkinson’s found that about 46% of them reported relief from their overall symptoms. (Venderová, 2004) Important to note, however, improved feelings occurred at an average of 1.7 months after the first use of marijuana, which suggests that long-term use may be necessary to alleviate some Parkinson’s symptoms, which could potentially lead users to develop dependence on the drug. Bradykinesia was the most common symptom that was alleviated, followed by muscle rigidity and tremors, with participants reporting a “calming effect” on tremors and dyskinesia with the use of marijuana. (Robledo, 2017)
Overall, more research needs to be conducted in order to truly understand what the link is between CBD and THC in their protective effects against neurodegenerative disorders. However, what these studies do tell us is that cannabis does in fact have a number of medicinal benefits, even outside of just possibly treating NDs. Past research has already demonstrated that cannabis may reduce seizure frequency in children and young adults with highly treatment-resistant epilepsy, suggesting that certain properties of cannabinoids may potentially be useful in treating other ailments. (Devinsky, 2016) Hopefully restrictions on cannabis, more specifically on THC, will be lifted in certain realms so researchers can more effectively examine how exactly these cannabinoids may facilitate individuals fighting their own battles against varying diseases.
References:
Bhunia, S., Kolishetti, N., Arias, A. Y., Vashist, A., & Nair, M. (2022). Cannabidiol for neurodegenerative disorders: A comprehensive review. Frontiers in pharmacology, 13, 989717. https://doi.org/10.3389/fphar.2022.989717
Devinsky O, Marsh E, Friedman D, Thiele E, Laux L, Sullivan J, Miller I, Flamini R, Wilfong A, Filloux F, Wong M, Tilton N, Bruno P, Bluvstein J, Hedlund J, Kamens R, Maclean J, Nangia S, Singhal NS, Wilson CA, Patel A, Cilio MR. Cannabidiol in patients with treatment-resistant epilepsy: an open-label interventional trial. Lancet Neurol. 2016 Mar;15(3):270-8. doi: 10.1016/S1474-4422(15)00379-8.
Kim, S. H., Yang, J. W., Kim, K. H., Kim, J. U., & Yook, T. H. (2019). A Review on Studies of Marijuana for Alzheimer’s Disease – Focusing on CBD, THC. Journal of pharmacopuncture, 22(4), 225–230. https://doi.org/10.3831/KPI.2019.22.030
Patel, R. S., Kamil, S., Shah, M. R., Bhimanadham, N. N., & Imran, S. (2019). Pros and Cons of Marijuana in Treatment of Parkinson’s Disease. Cureus, 11(6), e4813. https://doi.org/10.7759/cureus.4813
Robledo I, Jankovic J. (2017) Media hype: patient and scientific perspectives on misleading medical news. Mov Disord; 32:1319–1323.
U.S. Department of Health and Human Services. (2022). Neurodegenerative Diseases. National Institute of Environmental Health Sciences. Retrieved May 6, 2023, from https://www.niehs.nih.gov/research/supported/health/neurodegenerative/index.cfm#:~:text=Alzheimer%27s%20disease%20and%20Parkinson%27s%20disease,Alzheimer%27s%20Disease%20Association%20in%202022
Venderová K, Růzicka E, Vorísek V, Visnovský P. (2004). Survey on cannabis use in Parkinson’s disease: subjective improvement of motor symptoms. Mov Disord;19:1102–1106.
Wiatrak, B., Kubis-Kubiak, A., Piwowar, A., & Barg, E. (2020). PC12 Cell Line: Cell Types, Coating of Culture Vessels, Differentiation and Other Culture Conditions. Cells, 9(4), 958. https://doi.org/10.3390/cells9040958
On Psychology and Neuroscience 
This is a super interesting article! While it is unfortunate that there is no cure or prevention method for neurodegenerative disease yet, the use of cannabis to slow the effects seems promising. I was wondering if cannabis must be consumed after or before the onset of the disease, and if using it at. a young age may decrease the likelihood of developing these disorders later on in life when they usually present themselves. I would also be worried about the likelihood that a patient would grow dependent on cannabis during treatment. I would suggest defining words such as demyelination and antioxidant effects so readers have a better understanding of the biological effects of cannabis treatment in NDs. I like how you propose future healthcare solutions in the last paragraph. Great article!
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Hi Mason,
This was a very interesting read and posses several good questions that can hopefully be answered in the near future. One part of this article that stood out to me was on the increase in improved feelings after continuous marijuana use. I always though of marijuana to be a drug that takes action pretty quickly after consumption so I think it would be interesting to explore how patients with NDs see results so much later on in the treatment (1.7 months later). However, it also leads me to wonder about the potential risks associated with long-term marijuana use, particularly with patients who may be at a higher risk for dependency or addition. This article has certainly given readers and researchers a lot to think about and look into. Good job!
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This is a very interesting post. I think you ask some great questions as well as provide insightful evidence from research showing some potential benefits. Something I do find interesting though, is how marijuana can be helpful for Alzheimer’s. In another class, I did research on the relationship between Alzheimer’s and sleep. As it turns out, sleep is incredibly important for clearing out protein build-ups. Accumulation of these proteins forms plaques and tangles, which are key biomarkers for Alzheimer’s. It’s interesting, then, that marijuana blocks REM sleep but is still a powerful tool in protecting patients from symptoms. It’s a bit of a paradox in my view. I’m curious as to what the specific mechanisms are regarding marijuana and sleep, and how this can tie in with Alzheimer’s as well as other neurodegenerative diseases. Great post!
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Thanks for this blog post, Mason. It would have been good to explain the role of the immune system in neurodegenerative disease. This would make it more clear as to why the anti-inflammatory effects of cannabis may aid in treating neurodegenerative diseases.
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