Parkinson’s plant therapies show promise—but cannabis falls short

Levodopa remains the cornerstone of Parkinson's disease (PD) treatment; however, long-term use is associated with motor complications, including fluctuations and dyskinesia. Non-motor symptoms also worsen over time, reflecting both disease progression and treatment-related effects. These limitations have prompted interest in plant-derived therapies as potential adjunctive options, although clinical evidence remains unclear. To systematically review clinical evidence on plant-derived therapies in PD, focusing on motor symptoms, non-motor symptoms, and motor complications. PubMed, Scopus, and ScienceDirect were searched to identify eligible studies assessing plant-derived therapies for PD. Risk of bias and evidence classification were assessed using established methods. The review followed PRISMA 2020 guidelines and was registered in PROSPERO (CRD420261276805). Twenty-three included studies evaluated six plant-derived therapies. Mucuna pruriens was supported by Grade A evidence for motor improvement, with benefits comparable to levodopa and increased ON time without worsening dyskinesia. It also reduced dyskinesia (Grade B). Apium graveolens improved motor symptoms, sleep, and quality of life (Grade B). Curcuma longa improved autonomic and non-motor symptoms (Grade C). Bacopa monnieri improved emotional symptoms (Grade B). Glycine max increased ON time and reduced dyskinesia (Grade C). Cannabis sativa showed no motor benefit (Grade A), with inconclusive non-motor outcomes. Selected plant-derived therapies may offer symptom-specific benefits in PD. However, the available evidence is limited, and grading reflects study hierarchy rather than the certainty of clinical effect. Therefore, interpretation of this information should be cautious. Larger, well-designed randomised trials are required to confirm efficacy and safety.