Detailed analysis of selected pathological conditions and effects of cannabis and its derivatives with weaker clinical evidence and a strong theoretical basis favoring effectiveness. With reference to Parkinson’s disease.
A short quote from the .pdf (a link to the detailed analysis is at the end of this post).
” Parkinson’s disease
This disease, whose symptoms especially include a decrease in the number of dopaminergic neurons in the basal ganglia (“BG”), is, due to its high prevalence (especially among older patients) and simultaneous existence of endocannabinoid receptors in the BG system, often cited as a potential aim of therapy with cannabis [61, 62]. It is also known that oftentimes patients themselves experiment with cannabis for treatment – e.g. in an anonymous questionnaire from the Movement Disorders Center of the Clinic of Neurology of the 1st Medical Faculty and General Teaching Hospital, Charles University in Prague, up to 25% patients mentioned experimenting with cannabis, and nearly half of them stated a subjective improvement of their condition . However, there exist relatively few clinical trials on the given topic and they exhibited mixed results. A well known study from 2004 did not prove for levodopa-induced dyskinesia in 17 Parkinson’s disease patients any statistically significant improvement in consequence of using an oral extract from cannabis ; on the contrary, a new study 10 years more recent of 22 patients  identified significant improvement in the Unified Parkinson’s Disease Rating Scale 30 minutes after smoking cannabis, and it found statistically significant improvement also among specific motor symptoms of the type – tremor, rigidity, bradykinesia and others, and moreover without serious side effects. Chagas et al. experimented for Parkinson’s disease with pure CBD; their most thoroughly elaborated study on 22 patients did not find by objective measuring any statistically significant differences between the placebo group, the group with the dose of 75 mg and 350 mg daily; such differences however were found in perceiving quality of life . Though there exists a theoretical basis supporting the effectiveness of cannabis and/or substances derived from it for alleviating symptoms of Parkinson’s disease, there still exist few quality clinical trials with a sufficient number of patients, which would reliably verify such effectiveness. According to Barnes & Barnes (2016), it is possible to consider as merely limited the clinical evidence supporting the effectiveness of cannabis and its derivatives for treating Parkinson’s disease and/or its symptoms. Trials with pure CBD need not be completely relevant as the entourage effect (see Discussion) is not reflected in their designs.”