First, a set of molecular studies in fresh lymphocytes will examine the expression levels in target genes (namely BCL2, BAX, p53, SAT1) and protein (BDNF), and the activity of Complex I (all biological measures already known to be up-/down- regulated by lithium) at T0 and T1. These biological measures will serve as an assay sensitivity. We expect them to be regulated by in vivo lithium treatment and consequently to be significantly different between T0 and T1 in fresh lymphocytes.