Low, but not high, doses of melatonin entrained a free-running blind person with a long circadian period

@article{Lewy2002LowBN,
  title={Low, but not high, doses of melatonin entrained a free-running blind person with a long circadian period},
  author={Alfred J. Lewy and Jonathan S. Emens and Robert Sack and Brant P. Hasler and Rebecca A. Bernert},
  journal={Chronobiology International},
  year={2002},
  volume={19},
  pages={649 - 658}
}
In a previous report, we were unable to entrain one out of seven totally blind people with free-running endogenous melatonin rhythms to 10 mg of exogenous melatonin. This person had the longest circadian period (24.9 h) of the group. We now find that this person can be entrained to 0.5 mg of melatonin, but not to 20 mg. These results are consistent with the idea that too much melatonin may spill over onto the wrong zone of the melatonin phase–response curve. 
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