Faustino PR, Duarte GS, Chendo I, et al. - A systematic review and meta-analysis were performed to evaluate the correlation of bipolar disorder (BD) with a later diagnosis of idiopathic Parkinson disease (PD). Researchers included seven studies involving a total of 4,374,211 individuals. They conducted an electronic literature search of Cochrane Controlled Register of Trials, MEDLINE, Embase, and PsycINFO from database inception to May 2019 using the terms Parkinson disease, bipolar disorder, and mania, with no constraints used. In comparison with the general population, individuals with BD have a significantly increased risk of developing PD. Subgroup analyses implied a possible overestimation in the magnitude of the correlations. It was indicated that the probability that BD may be linked with later development of PD and the importance of the differential diagnosis of parkinsonism features in people with BD.