Polymorphisms (SNPs) in clock genes have been associated with the development of anxiety disorders, depression, and sleep disorders, and it has been found that circadian clock genes have a wide range of physiological effects on cognition, mood, and sleep behavior and that mutations in them can lead to mood disorders, imbalances in the sleep–wake cycle, and changes in the organism’s metabolic levels (23–25). This evidence concerns the gene CLOCK and depressive symptom measurement.