In a genetic association study with 19 circadian genes in the Spanish population, Soria et al. [21] reported that nine circadian genes (ADCYAP1, ARNTL, ARNTL2, CLOCK, CRY1, NPAS2, PER3, VIP, and VIPR2) exhibited nominal significance for major depressive disorder (MDD), whereas 3 genes (BHLHB3, CSNK1E, and RORA) were significantly associated with BD. Here, CLOCK is linked to major depressive disorder.