Many compounds present in cannabis appear to have neuroprotective properties, and scientists are increasingly looking at cannabinoids as candidates to treat a range of cognitive disorders.
From Alzheimer’s, Parkinson’s and other forms of dementia to stroke and traumatic brain injuries, the list of neurodegenerative conditions that cannabis may alleviate is continually growing. While research on this subject still has a way to go, evidence to support the neuroprotective potential of cannabis is starting to mount.
Evidence For The Neuroprotective Effect Of Cannabis
Already widely used to treat chronic pain and a range of other conditions, cannabinoids are believed to exert their therapeutic effects by reducing inflammation and oxidative stress. Crucially, both of these factors are highly pertinent when it comes to neurodegeneration, and are considered to be a major contributor to the development of dementia and other types of age-related cognitive decline.
Over the past decade or so, several studies have revealed the neuroprotective function of cannabis in mice. For instance, a paper published in 2012 indicated that a single microdose of THC was sufficient to boost neuronal growth factors in the rodents’ brains, thereby preventing neurons from becoming damaged by carbon monoxide or repeated doses of MDMA[i].
This was followed up by another study in 2017, in which aged mice that received daily doses of THC for four weeks tended to outperform those that weren’t treated with the cannabinoid on a range of cognitive tasks. Amazingly, the study authors found that 12-month-old mice that were treated with THC displayed patterns of hippocampal gene expression that matched those of two-month-old mice[ii].
While neither of these studies delved into the mechanisms behind the neuroprotective properties of cannabis, clues can be found in the role that the body’s own cannabinoids play in safeguarding neurons. Research has shown that when the brain suffers an injury, levels of endocannabinoids such as anandamide increase in the area around the insult, and serve to protect neurons from being damaged by inflammatory proteins and oxidants[iii]. Like anandamide, THC binds to the CB1 receptor, and can logically be expected to produce a similar effect.
How Does Cannabis Exert Its Neuroprotective Effects?
Cannabinoids are known to have anti-inflammatory and antioxidant properties in all areas of the body, although studying this phenomenon can be a little more complex in the brain. This is because the brain contains its own unique set of immune cells called astrocytes, which regulate inflammation and other processes.
Understanding the neuroprotective effect of cannabis, therefore, requires an appreciation of how cannabinoids interact with astrocytes. While research into this topic is ongoing, several studies have already shed light on how these compounds protect the brain.
For instance, in a rat model of Parkinson’s disease, animals that were treated with CBD displayed reduced neuroinflammation and improved motor control. Analysis revealed that the cannabinoid binds to capsaicin receptors on the surface of astrocytes, triggering the release of a neuroprotective growth factor[iv].
Separate studies have shown that both CBD and CBG contribute the neuroprotective function of cannabis by binding to serotonin receptors[v]. A reduction in serotonin signalling is a major hallmark of several neurodegenerative disorders, and the fact that these cannabinoids help to restore proteins that are essential to the release of this key neurotransmitter indicates that they may have a massive role to play in the fight against cognitive decline[vi].
Of course, animal research is only a starting point for investigating the therapeutic suitability of cannabis, and findings can’t always be replicated in people. At present, no large-scale clinical trials have been conducted to determine the efficacy of cannabinoids at protecting brain cells in living humans.
However, with a wealth of pre-clinical research pointing towards a strong neuroprotective effect, it seems reasonable to view cannabis as one of our brains’ most important allies.
[i] Miriam Fishbein, Sahar Gov, Fadi Assaf, Mikhal Gafni, Ora Keren, Yosef Sarne. Long-term behavioral and biochemical effects of an ultra-low dose of Δ9-tetrahydrocannabinol (THC): neuroprotection and ERK signaling. Experimental Brain Research, 2012; 221 (4): 437 – https://link.springer.com/article/10.1007%2Fs00221-012-3186-5
[ii] Bilkei-Gorzo A, Albayram O, Draffehn A, Michel K, Piyanova A, Oppenheimer H, Dvir-Ginzberg M, Rácz I, Ulas T, Imbeault S, Bab I. A chronic low dose of Δ 9-tetrahydrocannabinol (THC) restores cognitive function in old mice. Nature medicine. 2017 Jun;23(6):782. – https://www.nature.com/articles/nm.4311
[iii] Sarne Y, Toledano R, Rachmany L, Sasson E, Doron R. Reversal of age-related cognitive impairments in mice by an extremely low dose of tetrahydrocannabinol. Neurobiology of aging. 2018 Jan 1;61:177-86. – https://www.sciencedirect.com/science/article/abs/pii/S1471491402022761
[iv] Giuliano C, Francavilla M, Ongari G, Petese A, Ghezzi C, Rossini N, Blandini F, Cerri S. Neuroprotective and Symptomatic Effects of Cannabidiol in an Animal Model of Parkinson’s Disease. International Journal of Molecular Sciences. 2021 Jan;22(16):8920. – https://www.mdpi.com/1422-0067/22/16/8920
[v] Echeverry C, Prunell G, Narbondo C, de Medina VS, Nadal X, Reyes-Parada M, Scorza C. A Comparative In Vitro Study of the Neuroprotective Effect Induced by Cannabidiol, Cannabigerol, and Their Respective Acid Forms: Relevance of the 5-HT 1A Receptors. Neurotoxicity Research. 2021 Apr;39(2):335-48.- https://link.springer.com/article/10.1007/s12640-020-00277-y
[vi] di Giacomo V, Chiavaroli A, Recinella L, Orlando G, Cataldi A, Rapino M, Di Valerio V, Ronci M, Leone S, Brunetti L, Menghini L. Antioxidant and neuroprotective effects induced by cannabidiol and cannabigerol in rat CTX-TNA2 astrocytes and isolated cortexes. International journal of molecular sciences. 2020 Jan;21(10):3575. https://www.mdpi.com/1422-0067/21/10/3575/htm