Besides gene expression studies, LCLs have also been used to investigate the effect of lithium on protein levels in BD subjects. The study from Tseng et al. (2008) revealed that basal BDNF protein levels are decreased in LCLs from lithium responsive BD patients when compared with both their unaffected relatives and with healthy control participants. Interestingly, in vitro treatment with lithium of the LCLs decreased BDNF levels in all participants, but the difference between BD patients and healthy controls remained.