Additional blood-based PD therapeutic targets that lithium may engage include serum brain-derived neurotrophic factor (BDNF), plasma alpha-synuclein and the inhibited form of glycogen synthase kinases-3β phosphorylated at serine 9 (pS9-GSK3β), in PBMCs (Li et al., 2007; Leyhe et al., 2009; Lin et al., 2017). This evidence concerns the gene BDNF and Parkinson disease.