Individuals with PD were enrolled ifthey were within 2 years of diagnosis, Hoehn and Yahr (H&Y) stage 1–2, not on PDmedications at the time of enrollment, and had an abnormal dopamine transporter(DAT) imaging scan with single-photon-emission computed tomography (SPECT).Inclusion criteria for the genetic PD cohort were the same, except for PDmedications, and diagnosis within 7 years were allowed. The gene discussed is SLC6A3; the disease is Parkinson disease.