Plymouth, United Kingdom: Short-term use of oral THC does not mitigate symptoms of dyskinesia (impairment of voluntary movement) in patients with Parkinson's Disease (PD), according to clinical trial data published in the journal Neurology.
Nineteen volunteers participated in the randomized, double-blind, placebo-controlled crossover trial. Patients were administered oral THC for a period of four weeks.
"Cannabis was well tolerated, [but] had no pro- or antiparkinsonian action," authors concluded, though they acknowledged that prior clinical and animal model data "support the view that modulation of cannabinoid function may exert an antidyskinetic effect."
One possible explanation for the study's outcome may be that patients enrolled in the trial did not use THC for a long enough duration to experience objective relief. According to survey data published last month in the journal Movement Disorders, PD patients who said they used cannabis for at least two months "reported significantly more often a mild or substantial alleviation of their PD symptoms in general" than those who had only used cannabis short-term.
"The late onset of cannabis action is noteworthy," authors of the survey wrote. "Because most patients reported that improvement occurred approximately two months after the first use of cannabis, it is very unlikely that it could be attributed to a placebo reaction."
Clinical studies of patients with other neurodegenerative disorders such as Multiple Sclerosis have also suggested that cannabis may provide more significant relief if used over longer periods of time. Most recently, a 52-week follow up trial of more than 500 multiple sclerosis patients found that participants gained significantly greater relief of disabling symptoms after one year of cannabinoid therapy than they did after 15 weeks. "In the short-term study, there was some evidence of cannabinoids alleviating symptoms of multiple sclerosis; in the longer term there is a suggestion of a more useful beneficial effect, which was not clear at the initial stage," the study's author noted.
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