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The idea of using marijuana to treat Alzheimer’s is still not widely recognized. But treatment options for Alzheimer’s are currently limited, and research over the years has now led scientists to believe cannabis, or components of the plant known as cannabinoids, could be the answer.
This month, two scientists with the Spanish Biomedical Research Networking Centre (CIBER) published a review in Frontiers of Pharmacology highlighting the potential benefits of cannabis-based treatments and calling for clinical research to be conducted.
Inflammation of the brain plays a major role in Alzheimer’s disease. Inflammatory activity of the brain’s immune cells is thought to contribute to the progressive loss of neurons that underlies the disorder.
As it turns out, compounds in marijuana act on targets found on immune cells called CB2 receptors. Several studies have found that activation of CB2 receptors can reduce neuroinflammation in Alzheimer’s disease models.
Besides CB2 receptors, THC also acts on CB1 receptors. CB1 activity may also interfere with the inflammatory process, according to a 2012 study published in the Journal of Alzheimer’s Disease.
The accumulation of beta-amyloid (Aβ) plaque in the brain is a primary hallmark of Alzheimer’s disease. These plaques are highly visible in brain scans of patients, and are believed to play a role in the loss of neurons.
Studies have shown that certain cannabinoids can protect neurons against Aβ plaque and its effects. For example, researchers have found that THC can prevent memory deficits in Aβ-injected rats.
Cannabinoids may also be effective at preventing the formation of plaque, according to a 2006 study published in Molecular Pharmaceutics. The study concluded: “Compared to currently approved drugs prescribed for the treatment of Alzheimer’s disease, THC is a considerably superior inhibitor of Aβ aggregation.”
The main concerns of health professionals regarding the use of marijuana-based treatments are related to the ‘high’ caused by certain cannabinoids, mainly THC. While it’s true that THC’s effect on the brain can disrupt memory and attention, this is not as big of a barrier in treating Alzheimer’s as some might think.
In fact, studies conducted so far suggest the therapeutic effects of psychoactive cannabinoids, including THC, can be achieved at low enough doses to avoid causing a high.
What’s more, cannabis contains a number of other potentially useful compounds that are not psychoactive. For example, a 2014 study published in Psychopharmacology found the non-psychoactive cannabinoid CBD to be effective at reversing memory deficits in animal models of Alzheimer’s disease.
Neurogenesis is the growth of new brain cells that occurs throughout adulthood. A disruption of this process is thought to be an early event in Alzheimer’s that prevents neurons from regenerating once progressive cell loss begins.
Various cannabinoids, including CBD, have been shown to promote neurogenesis in response to disruption caused by Aβ plaque.
Also, a 2004 study published in the European Journal of Neuroscience found that cannabinoids could increase levels of brain-derived neurotrophic factor (BDNF). This protein is known to play a key role in promoting neurogenesis and brain plasticity.
Most drugs used for treating Alzheimer’s work by preventing the breakdown of a signalling molecule called acetycholine. Interestingly, in addition to their unique benefits, studies show cannabiniods can affect acetycholine in the same way as current medications.
THC has been found to inhibit AChE – the enzyme responsible for breaking down acetycholine – as well as the accumulation of Aβ plaque associated with AChE activity. AChE inhibitors are commonly prescribed to treat symptoms of dementia.