Sleep is essential for life. A good night's sleep is pleasurable and sleep deprivation is stressful. Prolonged sleep loss impairs temperature control, metabolism, immunity, and ultimately leads to death. Extensive observational and epidemiological evidence indicates that optimal sleep duration of 8 hours is associated with the maintenance of good health. In our society, however, most people only get 6.5 - 7 hours. Suboptimal sleep duration has a strong association with mortality and morbidity. Lack of sleep has been linked to cardiovascular diseases, obesity, hypertension, type 2 diabetes, and other health/cognition conditions. It is clear that the biological need for sleep varies dramatically among humans. Sleep and circadian disorders can include Familial Advanced Sleep Phase (FASP), Delayed Sleep Phase (DSP), Advanced Sleep Phase (ASP), Natural Short Sleepers (NSS) or Long Sleeping. In example, Natural Short Sleepers (NSS) have a lifelong tendency to... (for more see dbGaP study page.)