This review is dedicated to research on cannabinoids and Parkinson’s disease. It summarizes some research results and what we know so far about cannabis and Parkinson’s disease.
Parkinson’s disease is a progressive neurodegenerative disease, which is characterized by slow movement, rigidity of muscles, tremor at rest and loss of postural reflexes. It is a result of loss of neurons. While in 90-95% of the patients the cause of the disease is unknown, in 5-10% of the cases it is family-inherited disease.
Let’s start with a bit of a history: Tincture of Cannabis indica and belladona alkaloids were prescribed for Parkinson’s disease in 18th century.
Survey sent via email to patients with Parkinson’s (339 participants) showed that 25% of them use cannabis leaves orally and only 1 patient smoked cannabis. Patients have used cannabis at least 3 months. After starting to use cannabis, 39 patients (45.9 %) reported mild or substantial alleviation of their PD symptoms in general, 26 (30.6 %) improvement of tremor, 38 (44.7 %) alleviation of bradykinesia, 32 (37.7 %) alleviation of muscle rigidity. Four patients (4.7 %) claimed that cannabis actually worsened their symptoms.
There are other small size clinical trials, which aimed to examine the effect of cannabis on patients with Parkinson’s disease but their results are inconclusive. 
The discovery of the endocannabinoid system showed that endocannabinoids are involved in the control of movement. This was confirmed when endocannabinoid receptors (CB1 and CB2) were discovered in basal ganglia and cerebellum, which control movements.
Further research in animal models (mice) have shown that in Parkinson’s disease the endocannabinoids are overactivated in the basal ganglia. Application of synthetic AEA and THC and synthetic cannabinoids inhibit motor activity and produce catalepsy. 
While there is a need of more research, recently discovered mechanisms in endocannabinoid system suggests that cannabinoids may play important role in Parkinson’s disease.