Finally, several SNPs in genes of the circadian rhythm unexplored with cognition previously were evaluated in cancer patients: rs1801260 in CLOCK (Circadian Locomotor Output Cycles Kaput), rs934945 in PER2 (Period circadian regulator 2), and rs10838524 CRY2 (Cryptochrome circadian regulator 2). Here, PER2 is linked to cancer.