Project Description

Definition

parkinsons-disease (1)Parkinson’s disease (PD, also known as idiopathic or primary parkinsonism, hypokinetic rigid syndrome/HRS, or paralysis agitans) is a degenerative disorder of the central nervous system. The motor symptoms of Parkinson’s disease result from the death of dopamine-generating cells in the substantia nigra, a region of the midbrain; the cause of this cell death is unknown. Early in the course of the disease, the most obvious symptoms are movement-related; these include shaking, rigidity, slowness of movement and difficulty with walking and gait. Later, thinking and behavioral problems may arise, with dementia commonly occurring in the advanced stages of the disease, whereas depression is the most common psychiatric symptom. Other symptoms include sensory, sleep and emotional problems. Parkinson’s disease is more common in older people, with most cases occurring after the age of 50.

The main motor symptoms are collectively called parkinsonism, or a “parkinsonian syndrome”. Parkinson’s disease is often defined as a parkinsonian syndrome that is idiopathic (having no known cause), although some atypical cases have a genetic origin. Many risk and protective factors have been investigated: the clearest evidence is for an increased risk of PD in people exposed to certain pesticides and a reduced risk in tobacco smokers. The pathology of the disease is characterized by the accumulation of a protein called alpha-synuclein into inclusions called Lewy bodies in neurons, and from insufficient formation and activity of dopamine produced in certain neurons within parts of the midbrain. Lewy bodies are the pathological hallmark of the idiopathic disorder, and the distribution of the Lewy bodies throughout the Parkinsonian brain varies from one individual to another. The anatomical distribution of the Lewy bodies is often directly related to the expression and degree of the clinical symptoms of each individual. Diagnosis of typical cases is mainly based on symptoms, with tests such as neuroimaging being used for confirmation.

Medical Marijuana Efficacy

According to a recent study published in Clinical Neuropharmacology, participants using smoked medical cannabis had significant improvements in motor disability and impairment. These results were found in addition to reported decreases in tremor (repetitive shaking), rigidity (stiffness or inflexibility), and dyskinesia (difficulty in performing voluntary movements), and improvements in pain and sleep disturbance. This study was flawed in that it included only 22 participants, there was no blinding to treatment (i.e. both the participants and researchers knew that they were using cannabis, which means that the results were potentially a result of “expectancy effects”), and they used a “within-subjects” design, which has well-documented weaknesses. Still, these results show that further study is appropriate and warranted.

In a study published in the Journal of Psychopharmacology in September 2014 found that treatment with 300 mg/day of the cannabinoid cannabidiol (CBD) in patients with Parkinson’s Disease, without dementia or comorbid psychiatric conditions (i.e. those occurring at the same time as the primary disease), increased well-being and quality of life compared to patients who had received the placebo (an inactive treatment used to attempt to control for “expectancy effects”).

However, there was no improvement in measures of motor (i.e. movement) and general symptoms, and no evidence for possible neuroprotective effects, and the sample size was small, with only 21 participants split into 3 groups (placebo, 75 mg/day CBD, and 300 mg/day CBD). In spite of the lack of significance in certain measures and the small sample size, these results are impressive, especially given that the increase in well-being and quality of life resulted from use of a non-psychoactive cannabinoid.

Research into the relationship between THCV and tremors associated with Parkinson’s has suggested a significant reduction in erratic, uncontrolled movement.

Official Research Reports

Survey on cannabis use in Parkinson’s disease: subjective improvement of motor symptoms. (Venderová K, Růzicka E, Vorísek V, Visnovský P, 2004)

Cannabis for dyskinesia in Parkinson disease: a randomized double-blind crossover study. (Carroll CB, Bain PG, Teare L, Liu X, Joint C, Wroath C, Parkin SG, Fox P, Wright D, Hobart J, Zajicek JP, 2004)

Cannabinoids reduce levodopa-induced dyskinesia in Parkinson’s disease: a pilot study. (Sieradzan KA, Fox SH, Hill M, Dick JP, Crossman AR, Brotchie JM, 2001)

The effects of the cannabinoid receptor agonist nabilone on L-DOPA induced dyskinesia in patients with idiopathic Parkinson’s disease (PD). (Sieradzan KA, Fox SH, Dick J, Brotchie JM, 1998)

Marijuana for parkinsonian tremor. (J P Frankel, A Hughes, A J Lees, G M Stern, 1990)

Open label evaluation of cannabidiol in dystonic movement disorders. (Consroe P, Sandyk R, Snider SR, 1986)

Beneficial and adverse effects of cannabidiol in a Parkinson patient with sinemet-induced dystonic dyskinesia. (Snider SR, Consroe P, 1985)

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