The results of association between the Per3 gene and BD in our sample may bring additional evidence to the former findings of association between the Per3 gene and BD.
Several circadian genes have been found to be associated with bipolar disorders: at least three studies have reported positive associations for each of CLOCK, NPAS2, ARNTL1, NR1D1, PER3, RORB and CSNK1epsilon.
Analysis of clock gene variants revealed that PER3 and RORA genotype predicted period lengthening by Li, whereas GSK3β genotype predicted rhythm effects of Li, specifically among BD cases.
Such connections to circadian genes such as CLOCK, ARNTL1, NPAS2, PER3 and NR1D1 have been repeatedly demonstrated for bipolar disorders, and to a lesser extent for recurrent depressive disorders and seasonal affective disorders.
We have assessed evidence for linkage and association involving polymorphisms in 10 circadian clock genes (ARNTL, CLOCK, CRY2, CSNK1epsilon, DBP, GSK3beta, NPAS2, PER1, PER2, and PER3) to BPAD.