Parkinson’s Disease is most associated with compromised motor function after the loss of 60-80% of dopamine-producing neurons. As dopaminergic neurons become damaged or die and the brain is less able to produce adequate amounts of dopamine, patients may experience any one or combination of these classic PD motor symptoms: tremor of the hands, arms, legs or jaw; muscle rigidity or stiffness of the limbs and trunk; slowness of movement (bradykinesia); and /or impaired balance and coordination (postural instability).
Additional symptoms include decreased facial expressions, dementia or confusion, fatigue, sleep disturbances, depression, constipation, cognitive changes, fear, anxiety, and urinary problems. Pesticide exposure and traumatic brain injury are linked to increased risk for PD. Paraquat, an herbicide sprayed by the DEA in anti-marijuana defoliant operations in the United States and other countries, resembles a toxicant MPTP [methyl-phenyl-tetrahydropyridien], which is used to simulate animal models of Parkinson’s for research purposes.(2)
Within the PD brain there are an inordinate number of Lewy bodies - intracellular aggregates of difficult to break down protein clusters - that cause dysfunction and demise of neurons.(3) This pathological process results in difficulties with thinking, movement, mood and behavior. The excessive presence of Lewy bodies, coupled with the deterioration of dopaminergic neurons, are considered to be hallmarks of Parkinson’s. But mounting evidence suggests that these aberrations are actually advanced-stage manifestations of a slowly evolving pathology.
It appears that non-motor symptoms occur for years before the disease progresses to the brain, and that PD is actually a multi-system disorder, not just a neurological ailment, which develops over a long period of time. According to the National Parkinson’s Foundation, motor symptoms of PD only begin to manifest when most of the brain’s dopamine-producing cells are already damaged.
Patients whose PD is diagnosed at an early stage have a better chance of slowing disease progression. The most common approach to treating PD is with oral intake of L-dopa, the chemical precursor to dopamine. But in some patients, long-term use of L-dopa will exacerbate PD symptoms. Unfortunately, there is no cure – yet.
Defined as “the collection of all the microorganisms living in association with the human body,” the microbiome consists of “a variety of microorganisms including eukaryotes, archaea, bacteria and viruses.” Bacteria, both good and bad, influence mood, gut motility, and brain health. There is a strong connection between the microbiome and the endocannabinoid system: Gut microbiota modulate intestinal endocannabinoid tone, and endocannabinoid signaling mediates communication between the central and the enteric nervous systems, which comprise the gut-brain axis.What causes Parkinson’s? One theory that is gaining favor among medical scientists traces the earliest signs of PD to the enteric nervous system (the gut), the medulla (the brainstem), and the olfactory bulb in the brain, which controls one’s sense of smell. New research shows that the quality of bacteria in the gut – the microbiome – is strongly implicated in the advancement of Parkinson’s, the severity of symptoms, and related mitochondrial dysfunction.
Viewed as “the second brain,” the enteric nervous system consists of a mesh-like web of neurons that covers the lining of the digestive tract – from mouth to anus and everything in between. The enteric nervous system generates neurotransmitters and nutrients, sends signals to the brain, and regulates gastrointestinal activity. It also plays a major role in inflammation.
The mix of microorganisms that inhabit the gut and the integrity of the gut lining are fundamental to overall health and the ability of the gut-brain axis to function properly. If the lining of the gut is weak or unhealthy, it becomes more permeable and allows things to get into the blood supply that should not be there, negatively impacting the immune system. This is referred to as “leaky gut.” Factor in an overgrowth of harmful bacteria and a paucity of beneficial bacteria and you have a recipe for a health disaster.
The importance of a beneficial bacteria in the gut and a well-balanced microbiome cannot be overstated. Bacterial overgrowth in the small intestine, for example, has been associated with worsening PD motor function. In a 2017 article in the European Journal of Pharmacology, titled “The gut-brain axis in Parkinson’s disease: Possibilities for food-based therapies,” Peres-Pardo et al examine the interplay between gut dysbiosis and Parkinson’s. The authors note that “PD pathogenesis may be caused or exacerbated by dysbiotic microbiota-induced inflammatory responses … in the intestine and the brain.”(4)
Mitochondria, microbiota and marijuana
The microbiome also plays an important role in the health of our mitochondria, which are present in every cell in the brain and body (except red blood cells). Mitochondria function not only as the cell’s power plant; they also are involved in regulating cell repair and cell death. Dysfunction of the mitochondria, resulting in high levels of oxidative stress, is intrinsic to PD neurodegeneration. Microbes produce inflammatory chemicals in the gut that seep into the bloodstream and damage mitochondria, contributing to disease pathogenesis not only in PD but many neurological and metabolic disorders, including obesity, type-2 diabetes, and Alzheimer’s.
The evidence that gut dysbiosis can foster the development of PD raises the possibility that those with the disease could benefit by manipulating their intestinal bacteria and improving their microbiome. Enhancing one’s diet with fermented foods and probiotic supplements may improve gut health and relieve constipation, while also reducing anxiety, depression and memory problems that afflict PD patients.
Cannabis therapeutics may also help to manage PD symptoms and slow the progression of the disease. Acclaimed neurologist Sir William Gowers was the first to mention cannabis as a treatment for tremors in 1888. In his Manual of Diseases of the Nervous System, Grower noted that oral consumption of an “Indian hemp” extract quieted tremors temporarily, and after a year of chronic use the patient’s tremors nearly ceased.
Modern scientific research supports the notion that cannabis could be beneficial in reducing inflammation and assuaging symptoms of PD, as well as mitigating disease progression to a degree. Federally-funded preclinical probes have documented the robust antioxidant and neuroprotective properties of CBD and THC with “particular application … in the treatment of neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease and HIV dementia.” Published in 1998, these findings formed the basis of a U.S. government patent on cannabinoids as antioxidants and neuroprotectants.