PER2 and major depressive disorder: Inaddition, many of the selection variants in the PER1, PER2,PER3 genes appear to regulate biological processes that are associatedwith major modern diseases including obesity, cancer,metabolic syndrome, bipolar personality disorder, depression,rheumatoid arthritis, diabetes mellitus, lupus erythematosus,stroke and Alzheimer’s disease, making them extremely interestingtargets for further research aimed at identifying causalvariants of human diseases, including cardiometabolic andpsychiatric disorders, as well as cancer.