Pathophysiology of Circadian Rhythm Delayed Sleep Wake Phase Disorder

Participants will arrive approximately 8 hours before participant's scheduled bedtime to practice ability to think testing and a 9-hour sleep study. Participants will live in the laboratory for approximately 66 hours (2.75 days). Upon awakening in the morning, participants will start a routine of up to 39 hours of wakefulness, under bedrest conditions. Saliva will be sampled frequently and blood will be drawn 3 times. Reaction time, ability to think, and subjective rating tests will be performed frequently. Participants will be provided scheduled bathroom breaks when participants will use a commode next to the bed. Outside these scheduled bathroom breaks, participants will be provided a bedpan to use to go to the bathroom. At the end of the research procedures for Visit 4 participants will be given a recovery sleep opportunity and be discharged from the lab in the morning near participant's typical waketime.

Participants will arrive in the afternoon to practice ability to think testing and a 9-hour sleep study. Participants will live in the laboratory for approximately 48 hours (2 days). Upon awakening in the morning, participants will be exposed to dim candlelight and then later in the day alternating intensities of dim and room light when we keep participants awake for up to 23 hours (We will ask participants to remain in bed seated for \~12.5 hours). Saliva will be sampled frequently. Reaction time, ability to think, and subjective rating tests will be performed frequently. Participants will then have a second 9-hour sleep opportunity.