Melatonin phase shifts human circadian rhythms in a placebo-controlled simulated night-work study

Am J Physiol Regul Integr Comp Physiol. 2002 Feb;282(2):R454-63. doi: 10.1152/ajpregu.00135.2001.


There has been scant evidence for a phase-shifting effect of melatonin in shift-work or jet-lag protocols. This study tested whether melatonin can facilitate phase shifts in a simulated night-work protocol. Subjects (n = 32) slept in the afternoons/evenings before night work (a 7-h advance of the sleep schedule). They took melatonin (0.5 mg or 3.0 mg) or placebo before the first four of eight afternoon/evening sleep episodes at a time when melatonin has been shown to phase advance the circadian clock. Melatonin produced larger phase advances than placebo in the circadian rhythms of melatonin and temperature. Average phase advances (+/-SD) of the dim light melatonin onset were 1.7 +/- 1.2 h (placebo), 3.0 +/- 1.1 h (0.5 mg), and 3.9 +/- 0.5 h (3.0 mg). A measure of circadian adaptation, shifting the temperature minimum enough to occur within afternoon/evening sleep, showed that only subjects given melatonin achieved this goal (73% with 3.0 mg, 56% with 0.5 mg, and 0% with placebo). Melatonin could be used to promote adaptation to night work and jet travel.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adjuvants, Immunologic / administration & dosage*
  • Adult
  • Affect / drug effects
  • Body Temperature
  • Circadian Rhythm / drug effects*
  • Female
  • Humans
  • Jet Lag Syndrome / drug therapy
  • Male
  • Melatonin / administration & dosage*
  • Sleep / drug effects
  • Sleep Disorders, Circadian Rhythm / drug therapy*
  • Sleep Stages / drug effects
  • Work Schedule Tolerance


  • Adjuvants, Immunologic
  • Melatonin