Movement disorders can refer to a number of neurodegenerative and hyperkinetic disorders with motor symptoms such as resting tremors, akinesia, bradykinesia, spasticity, and loss of automatic movement. They can also be accompanied by autonomic dysfunction, cognitive impairment, and depression.
Given the recorded therapeutic potential of cannabis compounds, like cannabinoids, a number of studies have aimed to understand whether cannabis could potentially aid the treatment of some movement disorders. In a recent literature review, researchers assessed the current evidence for the use of cannabis and its derivatives in these conditions.
Cannabinoids and the Endocannabinoid System
There is evidence that cannabidiol (CBD) – a prevalent phytocannabinoid – may have therapeutic significance against neurodegenerative and hyperkinetic disorders. CBD-based medications have already been used to treat numerous symptoms and conditions, including intractable seizures, chronic pain, arthritis, post-traumatic stress disorder, and chemotherapy-associated nausea and vomiting.
The endocannabinoid system is the name given to a network of receptors, enzymes, and active compounds known as endocannabinoids. These compounds are similar in structure to the phytocannabinoids produced by cannabis plants. This similarity means that phytocannabinoids, such as CBD and tetrahydrocannabinol (THC) can effectively interact with endogenous cannabinoid receptors (CB1 and CB2), facilitating a number of responses and effects. The endocannabinoid system has been implicated in a number of cognitive and physiological functions, including mood, motor control, and pain.
Existing Evidence for Cannabis in Movement Disorders
A total of 22 relevant reports were included in the literature review, assessing a range of conditions, including multiple sclerosis (MS), Parkinson’s disease (PD), post-traumatic stress disorder (PTSD), and Huntington’s disease (HD).
However, the authors of this review placed particular focus on symptoms associated with Huntington’s disease, such as spasm and spasticity, tremor, sleep quality, and chorea. Motor and dystonia were also measured using the Unified Huntington’s Disease Rating Scale (UHDRS). This scale assesses the motor function, cognitive function, behavioural abnormalities, and functional capacity in patients living with HD.
Five of the studies and reports included in this review were randomised, placebo-controlled clinical trials which included a total of 1,329 human participants. These trials assessed the potential of various medical cannabis products, such as Sativex – an oral spray which combines CBD and THC, and synthetic cannabinoid, Nabilone.
The majority of studies included in this review demonstrated clinically significant results supporting the use of medical cannabis products in the treatment of movement disorders, particularly in for motor symptoms and sleep quality. However, the number of Huntington’s disease patients that were available to participate was relatively low, totalling just 78. Therefore, the examination of patients with similar symptoms (though caused by other conditions) was necessary.
The authors of this literature review acknowledge that the improvements in symptoms of movement disorders such as spasticity, tremors, chorea, and dystonia may be alleviated by both CBD and THC. On the other hand, symptoms such as sleep quality, behavioural and neuropsychiatric indices could be more attributable to CBD, given the cannabinoid’s anxiolytic, neuroprotective, antioxidant, and anti-convulsant properties.
The current evidence warrants the expansion of research in this area, with the authors recommending large scale, randomised, clinical trials to further progress our understanding of the potential of cannabis for the treatment of movement disorders, including Huntington’s disease.