Phase shifting the human circadian clock using melatonin

Alfred J. Lewy, Saeeduddin Ahmed, Robert L. Sack

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


Melatonin is produced only during nighttime darkness. Its onset during the evening is a useful marker for circadian phase position, when melatonin levels are sampled frequenly and under conditions of dim light or darkness. This marker is termed the dim light melatonin onset (DLMO). Recently, we have described a phase response curve (PRC) to melatonin in humans that is about 12 h out of phase with the PRC to light. Exogenous melatonin administration and bright light exposure can be used to shift circadian rhythms according to their respective PRCs. These phase-resetting agents can be used alone or together to treat circadian phase disorders, which include advanced and delayed sleep phase syndrome, shift work maladaptation, jet lag and winter depression. Endogenous melatonin may function to augment entrainment of circadian rhythms by the light-dark cycle.

Original languageEnglish (US)
Pages (from-to)131-134
Number of pages4
JournalBehavioural Brain Research
Issue number1-2
StatePublished - Dec 15 1995


  • Circadian phase sleep disorder
  • Circadian rhythm
  • Jet lag
  • Light
  • Melatonin
  • Phase response curve (PRC)
  • Serotonin
  • Shift work
  • Winter depression

ASJC Scopus subject areas

  • Behavioral Neuroscience


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