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Role of the Endocannabinoid System in Parkinson’s Disease
Endocannabinoid levels and CB receptors decrease with age and menopause [20]. Less cannabinoid signaling may mean less neuroprotection for dopamine cells, less ability to break down Lewy bodies, and other issues. No mutations in genes that regulate the endocannabinoid system have been identified in Parkinson’s disease; however, it likely that researchers have not pursued that as a possible mechanism of Parkinson’s disease yet. [19].
Clinical Research on Cannabis and Parkinson’s Disease
Both CBD and cannabis containing THC have been found to relieve symptoms of Parkinson’s disease. While only 4.3% of Parkinson’s patients used cannabis in one survey study, it was found to be among the most effective complementary and alternative medicine (CAM) treatments used [21]. Another survey of Parkinson’s patients using cannabis found 46% found some benefit; 45% had improvement of bradykinesia, 31% had improvement of resting
tremor, and 14% had improvement in levodopa-induced dyskinesia [22]. One clinical study found smoking cannabis with THC in it improved motor symptoms, tremor, brady-
kinesia, sleep, and pain in patients with Parkinson’s disease [23]. In a rodent model of Parkinson’s disease, the cannabinoid THCV reduced motor impairment and neurodegeneration [24].
A pilot study being conducted at University of Colorado School of Medicine by Dr. Maureen Leehey found Epidiolex (CBD from GW Pharmaceuticals) significantly improved Total Movement Disorder Society (MDS) and Motor MDS scores in Parkinson’s patients, but not rest tremor [25]. One clinical study found 300 mg of CBD a day improved quality of life but not motor symptoms in Parkinson’s patients, possibly due to it being in the lowest range necessary to see improvements in Parkinson’s patients [26]. Another study found CBD treatment decreased symptoms of rapid eye movement (REM) sleep behavior disorder in Parkinson’s patients [27]. Finally, psychosis in Parkinson’s disease is also treated by 150 mg of CBD a day for 4 weeks [28].
More research needs to be done on different dosages, ratios, and routes of administration of THC and CBD in Parkinson’s patients. Currently Michael J. Fox Foundation for Parkinson’s Research funds research on marijuana and Parkinson’s in Israel and supports the use of the compound in patients.