What is Delayed Sleep Phase Disorder?
Delayed sleep phase disorder (DSPD), officially called circadian rhythm sleep disorder, delayed sleep phase type, is an inability to fall asleep at a desired, conventional clock time and awaken at a socially acceptable morning time. When allowed to choose their preferred sleep schedule, patients exhibit sleep of normal quality and duration for their age and maintain a stable but delayed relationship of entrainment to the 24-hour, sleep-wake pattern.
Information provided by the National Sleep Foundation: