Are cannabinoids effective for Parkinson's disease?

It is postulated cannabinoids may have benefits in Parkinson's disease. However, its actual clinical effectiveness is still discussed. To answer this question, we used Epistemonikos, the largest database of systematic reviews in health, which is maintained by screening multiple information sources, including MEDLINE, EMBASE, Cochrane, among others. We identified six systematic reviews including eight studies overall, of which four were randomized trials relevant for the question of interest. We extracted data from the systematic reviews, reanalyzed data of primary studies included in these reviews, conducted a meta-analysis and generated a summary of findings table using the GRADE approach. We concluded cannabinoids probably do not decrease symptoms in Parkinson's disease or dyskinesia, and probably are associated to frequent adverse effects in patients with Parkinson's disease.