The time that we go to bed and wake up is generally determined by our work, study and social commitments. So, for the majority of people who work or study on a 9 a.m. to 5 p.m. pattern, a ‘normal’ sleep schedule would probably involve going to bed between 10 p.m. and midnight, and getting up between 6 a.m. and 8 a.m. in the morning. However, sufferers of circadian rhythm sleep disorders have circadian clocks that are not synchronised with such a ‘normal’ sleep schedule; instead their body clock is telling them to go to sleep and wake up at very different times. The relationship between their circadian clock and local time (local light/dark cycles) is abnormal.
