These factors can lead to a conflict between the body's sleep cues and the demands of society. Scientists are just beginning to understand how the circadian system works and what can be done to improve our ability to cope with these problems. For most, sleepiness begins in the early afternoon and results in an early bed time. Some people find that they are not able to fall asleep until 2 or 3am, and that they then have trouble waking up in time for work or school. This problem can interfere with both daily performance at work and school.
Some people seem to have a nonexistent or weakened circadian cycle.
They become sleepy after being awake only a few hours and then nap for a few hours. These napping sessions occur randomly throughout the day. The constant napping often ends up substituting for a full night's sleep. An abnormal circadian rhythm can be a symptom of depression or of poor sleep habits. In these cases, a sleep specialist should be consulted.