SLC6A3 and depressive disorder: Several studies have found that IRBD patients display clinical (e.g., hyposmia [20], depression [21], autonomic dysfunction [21]) and neuroimaging (e.g., decreased dopamine transporter binding in the striatum [22], substantia nigra hypechogenicity [22], increased mean diffusivity in the pons [23]) abnormalities which are characteristic features of the synucleinopathies.