CLOCK and bipolar disorder: Our current findings add to earlier gene expression studies in blood that have reported a number of potential peripheral biomarkers for bipolar disorder [50], [51], and earlier gene expression findings in brain indicating that clock genes are implicated in a model of bipolar disorder, the first report being [52], followed by [53] for CRY2. Circadian genes with a polymorphism previously reported to be associated to human bipolar disorder include CLOCK[54], and NR1D1, ARNTL and PER3[55]–[57].