National Sleep Foundation

Chapter 5: Circadian Rhythm Sleep Disorders

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.1-2

Advanced and delayed sleep phase 3

Fig 5.1 Advanced and delayed sleep phase


  1. American Academy of Sleep Medicine. The international classification of sleep disorders: diagnostic and coding manual. 2nd ed. Westchester, Ill: American Academy of Sleep Medicine; 2005.
  2. Weitzman ED, Czeisler CA, Coleman RM, et al. Delayed sleep phase syndrome: a chronobiological disorder with sleep onset insomnia. Arch Gen Psychiatry. 1981;38:737-746.
  3. Reid KJ and Zee PC. Circadian disorders of the sleep-wake cycle. In: Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 4th ed. Philadelphia, Pa: Elsevier Saunders; 2005:693.Pelayo RP, Thorpy M, Glovinsky P. Prevalence of delayed sleep phase syndrome among adolescents. J Sleep Res. 1988;17:392.