Some time ago one of our clinic's doctors - Dr. Glick - reviewed what is known about the connection between cannabis and Parkinson's disease.
In terms of understanding the activity of cannabis or preparations with cannabinoid activity on the brain, and in particular on the brain of a Parkinson's patient, an improvement in the parkinsonian symptoms is not expected, but perhaps even a worsening. At the same time, there may actually be an improvement in the dyskinesias that result from the drugs.

The connection between cannabis and Parkinson's has been tested and documented several times in the medical literature:
Over 20 years ago, after a Parkinson's patient who suffered from a severe and resistant tremor reported that smoking marijuana was very helpful. Following the report, a small cannabis study was conducted on 5 patients with Parkinson's disease accompanied by severe tremors. The study even found that one of the patients did not experience relief from tremors or other parkinsonian symptoms, despite the appearance of a feeling of sleepiness and euphoria.
In 2001, a randomized controlled trial was conducted that tested the effect of a dose of the cannabinoid agonist nabilone. The results in the seven patients who completed the study showed that nabilone is effective as a treatment for dyskinesias resulting from treatment with levodopa preparations, but does not improve parkinsonian symptoms or symptoms in response to levodopa.

In 2004, another randomized controlled study was published in which they tested the effect of the cannabinoid preparation cannador on dyskinesias as a result of treatment with levodopa. 17 patients completed the study but no beneficial effect on dyskinesias was observed. At the same time, no worsening of the parkinsonian syndrome was observed under treatment with this preparation, nor was there a decrease in the antiparkinsonian effect of levodopa.

Several years ago, after public exposure in the Czech media, Parkinson's patients in the Czech Republic started taking cannabis. An anonymous questionnaire study was then conducted, which were sent to a group of Parkinson's patients from a certain clinic. Out of 630 questionnaires sent, 339 were returned and 85 patients reported having used edible cannabis leaves. About half of them reported an improvement in their disease symptoms in general, about a third reported an improvement in tremors, almost half an improvement in bradykinesia, a third reported an improvement in rigidity, and a sixth reported an improvement in dyskinesias as a result of levodopa treatment. A small percentage reported that cannabis worsened their condition. Interestingly, the improvement most often occurred after almost two months of cannabis use on average. The criticism of the study was that it is not possible to separate the effect on the symptoms of the disease from a euphorogenic effect (good mood) and a general relaxing effect of the cannabis.
As of today, there is no recommendation for Parkinson's patients to take cannabis. There can be a variety of side effects that patients should be warned about, such as: sleepiness, memory loss, confusion, mental fogginess, and possibly hallucinations; There can also be a social price; The considerations are here and there and the patient must discuss all aspects with the attending neurologist.

Dr. Sharon Hassin, Director of the Parkinson's and Movement Disorders Clinic, Sheba Tel Hashomer Medical Center (from the Doctors Forum, the old website)