Figure 4.

Delayed Sleep Phase (DSP). Delayed sleep phase is the most common wakefulness-sleep challenge in adolescents and may lead to a DSP circadian sleep disorder. Individuals with DSP report difficulty falling asleep and difficulty awakening at the times required by school/work schedules. The phase delay in circadian timing, as indicated in this schematic by the later melatonin rhythm, may be related to biological (circadian physiology) and behavioral (e.g., social activities, increased light exposure in the evening, earlier school start times) changes that occur during adolescence. DSP combined with early school start times is thought to contribute to poor school performance and reduced sleep leading to chronic sleep loss during the week (open box).