Differential association of circadian genes with mood disorders: CRY1 and NPAS2 are associated with unipolar major depression and CLOCK and VIP with bipolar disorder.
Polymorphisms in the CLOCK, BMAL1, Per3 and TIMELESS genes have been associated with susceptibility to mood disorder, and single nucleotide polymorphisms and haplotypes in several circadian genes have been observed among those displaying certain circadian phenotypes, including worse mood in the evening, insomnia in mania and early, middle or late insomnia in depression.