SNCA and major depressive disorder: In summary, we have found, using a mixture of ELISAs and immunohistochemistry, no evidence that later-life depression is associated with an increase in insoluble Aβ or α-synuclein in the OFC or DLPFC, or increased immunolabelling of Aβ or hyperphosphorylated tau in the OFC, DLPFC or medial temporal lobe.