PER2 and sleep disorder: The CLOCK, PER2, and RORA genes of 748 mental workers (374 of whom were randomly selected from the sleep disorder group and 374 of whom were randomly selected from the normal sleep group) were genotyped by imLDRTM genotyping technology, and the relationship between CLOCK, PER2, and RORA gene polymorphisms and their interactions with sleep disorders were analyzed.