Joaquim Ferreira, MD, PhD, University of Lisbon, Lisbon, Portugal, reviews the learning points clinical trials have taught us about Parkinson's disease, from the etiology, pathogenesis, and progression. Usually, clinical trials are performed to evaluate the safety and efficacy of a novel treatment. However, clinical studies can provide great insights into aspects of the disease that are not related to the efficacy and safety of the evaluated drug. Particularly in Parkinson's disease, it is surprising how trials have shown that dyskinesias occur early with levodopa use and are probably not very disabling in the first 5 to 6 years. The methodology of clinical trials helps the field to have a systematic look, document, and report observations that could contribute to the progress of science. This interview took place at the European Academy of Neurology (EAN) 2022 Congress in Vienna, Austria.
