Psychiatric disorders often result from dysregulation in cellular and molecular mechanisms at the level of the brain. Unable to directly study brain tissues in patients affected by psychiatric conditions, researchers have created alternative experimental models that use different and easy to collect tissues. The underlying assumption is that by studying these "proxy" tissues, it is possible to obtain information on biological mechanisms that is a good approximation of what would be detected in the brain. One of the most established experimental models are lymphoblastoid cell lines derived from B-lymphocytes. Lymphocytes are present in the peripheral blood and can be easily collected and stored virtually forever after undergoing a special laboratory procedure that immortalize them. These cell lines have proved to be very useful in genetic and pharmacogenetic research and, using these, the investigators want to investigate the cellular effects of a mood stabilizing drug called lithium on this specific procedure that makes them virtually immortal. Two main reasons lead us to study this drug: 1) it is the most effective treatment in bipolar disorder, where approximately 30% of patients achieve complete illness remission with prevention of episode recurrence; 2) it has well established regulatory effects on the expression of specific target genes and proteins. The investigators can take advantage of these well-established properties of lithium in regulating the expression of genes, proteins, and enzymes in a stable manner. Conversely, these biological measures could be used as markers for the effects of lithium on the gene expression.