Getting up earlier than usual or sleeping a couple of hours late can have a significant effect on your mood, according to research published in 1997. When the body’s internal clock, or circadian (生理节奏的) rhythm, gets (67) of accord with your sleep-wake (68) , you can be left (69) out of sorts.
Researchers have long known that moods vary along (70) fluctuations in functions regulated by the body’s (71) 24-hour cycle rhythm, such as body temperature and hormone levels. The (72) of time a person has been awake is also known to (73) mood. To tease apart the two effects, U.S. and U.K. researchers (74) 24 healthy volunteers to live in (75) chambers for approximately three to five weeks and (76) their sleep-wake cycles to (77) a 30-hour or a 28-hour day, (78) than the 24-hour schedule (79) by the rotation of the Earth. Circadian rhythms, which are innate, remained (80) . While the subjects were awake, their mood was assessed (81) regular intervals.
The volunteers reported the (82) moods when their circadian rhythms were most out of line with their sleeping cycle. This (83) roughly to a schedule of sleeping during the day, from 2 P.M. to 10 P.M. Scores for mood were highest when the volunteers wake (84) between 6 A.M. and 2 P.M. The research may help explain the anxiety and (85) often reported by people who work night (86) and may suggest ways to manipulate mood.