By Dr. L.Tennant
Parkinson’s Disease (PD) is a chronic neurodegenerative disorder that affects over 100,000 Canadians today, with around 6,600 new cases being reported each year. The hallmark symptoms of the disease are tremors, rigidity, bradykinesia and postural instability. In the brain, the disease is characterized by the degradation of a specific type of cell, the nigrostriatal dopamine neurones, which causes in a deficiency in dopamine and leads to the motor, cognitive and neuropsychological impairments associated with the disease.
Current medications aim to restore the balance in dopamine levels to provide relief of motor symptoms, but they do not address the cause or the progression of the disease. For many patients, these medications produce side effects such as dyskinesia (abnormal involuntary movements) which needs to be controlled with further medication.
Medical cannabis and some of the active molecules derived from the Cannabis sativa plant are being investigated as potential therapies for PD both for the alleviation of motor and non-motor symptoms and for the potential to slow the progression of the disease. In this article we highlight some of the key findings in the clinical and experimental research of medical marijuana in PD, that was reported in a scientific article last year. To read the complete article click here.
Cannabis contains over 500 components and is one of the most studied plants chemically. Although many of the plants components can be found in other species, a group of chemicals called the phytocannabinoid compounds are unique. Of the phytocannabinoids, the most deeply studied and most abundant are delta-9Tetrahydrocannabinol (delta-9 THC) and cannabidiol (CBD). Delta-9 THC is a psychoactive and is the compound that is primarily responsible for the ´high’ of marijuana, it is also a potent analgesic and muscle relaxant. CBD works differently, it is not psychoactive, rather it seems to counteract delta-9 THC activity and reduce side effects of anxiety, tachycardia and hunger. At the cellular level, we know that the effects of phytocannabinoids are brought about by their interactions with the family of cannabinoid receptors and that these receptors orchestrate a wide number of cellular processes throughout the body. Relevant to PD, we now know that components of the cannabinoid system (the collective name for the endogenous cannabinoid compounds and their receptors) are abundant in the brain and are involved in regulating dopamine activity and motor functions. In PD the normal pathways of the endocannabinoid system are disrupted. Given the similarities between human (endogenous) and plant derived cannabinoids, it comes as no surprise that the phytocannabinoids have been proposed as potential therapies thanks to their ability to mediate the pathways involved in PD.
Using Cannabis for the treatment of the motor symptoms of PD is not new. In fact, the first reported case of successful treatment of PD patients with a Cannabis tincture was reported in 1888 by Dr William Gowers in his book ‘A Manual of Diseases of the Nervous System’. In the last decade a number of clinical studies have evaluated the effectiveness of medical marijuana and cannabinoids for the treatment of PD motor symptoms. For example, in 2004, a clinical study carried out in 339 patients with PD showed that 46% of patients that used marijuana experienced improvements in general PD related symptoms and in specific symptoms including resting tremor (31%), rigidity (38%), reduced bradykinesia (45%) and alleviated dyskinesia (14%). Symptomatic improvement was directly related to the concentration of THC metabolites in the urine. These findings have been seen in additional studies, where improvements in sleep and reduction in pain were also recorded. Follow this link to read the study reports.
While these studies focussed on motor symptoms, research has shown that medical marijuana can improve the quality of life of PD patients through the relief of non-motor symptoms including:
- Pain, the analgesic properties of cannabinoids are clinically well documented
- Depression, moderate use of cannabis can provide relief from depression
- Sleep disorders, the majority of PD patients suffer from sleep disorders and this negatively impacts their quality of life. Sleep problems can be caused by several factors including neurodegeneration and medication side effects.
Finally, research in-vitro and in mouse models of PD are examining the ability of cannabinoids to slow disease progression. Cannabinoids appear to have neuroprotective effects due to anti-inflammatory and anti-oxidative activity and their ability to suppress exitotoxicity (a process that causes nerve cell damage). As we understand more about the intricate mechanics of the endocannabinoid system in humans and how these are disrupted in PD, phytocannabinoids could offer much needed new therapeutic options for patients.