Lee KY, Song JY, Kim SH, Kim SC, Joo EJ, Ahn YM, Kim YS. Prog Neuropsychopharmacol Biol Psychiatry. 2010 Oct; 34 (7): 1196–1201.
A study of 610 Koreans was performed to determine whether circadian preferences and bipolar disorder can be influenced by genetics. It found a significant positive association between the rs1801260 SNP in the clock gene and bipolar disorder. The authors also discovered a trending but not significant relationship between this SNP and extreme morning or evening chronotype as measured by the Composite Scale of Morningness questionnaire.
rs1801260 in clock