SLC6A3 and major depressive disorder: The association between depression and the subsequent risk of developing PD is well described.8 23 The possibility that LOD is a prodromal feature of PD or DLB is further strengthened by this study which shows that the clinical features of motor and non-motor dysfunction seen in PD were more commonly present in those patients with LOD with an abnormal dopamine transporter scan than in those with a normal scan.