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Is melatonin properly produced in daytime sleep in full darkness? Or does it require only nighttime sleep?

Additionally, what other biological implications are there, if any, to daytime sleeping? Melatonin production is the only biological implication I could find so far.

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I think this question is answered by the answer I gave to another question.…. – rg255 Sep 23 '13 at 7:59
Thank you, but the main part of my question remains unanswered - is night required for melatonin production, or does it only require full darkness (such as in a dark room, blindfold, etc)? – UriP Sep 23 '13 at 22:45
"It is released by the pineal gland and production starts when the light fades, as it's production is inhibited by light stimulation of the retina, the onset of the production is called dim-light melatonin onset." – rg255 Sep 24 '13 at 5:59

The immediate thought came to my mind was relation between Melatonin and Serotonin. Because both hormones have sleep related function. I read that both are light sensitive. Melatonin is produced by pineal gland in brain whereas Serotonin is at gut and CNS.

Light dependence(Wikipedia) of Melatonin is explained here where they say blue light produces more Melatonin and wavelength of light <530nm will have effect on Melatonin production. If the light intensity is more then Melatonin will not be produced. So what they say is if there is darkness(artificial) or dim light environment then this hormone will be produced and induces sleep. Almost everywhere they explain Melatonin whose production is sensitive to light.

(But even in the afternoon when there is bright light some of us feel sleepy which is mainly due to Serotonin released after heavy meal which is produced from tryptophan. This will again effect the sleep. It is obvious that without food we can not sleep at night. So Serotonin and Melatonin are interrelated as explained here Link1 and Link2).

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Thank you for the detailed answer. However one part relevant to my question is still unanswered: is Melatonin also dependent on time, hour, day\night? If I am to stay in darkness during daytime, will Melatonin be produced as well as in the same darkness at night? – UriP Oct 2 '13 at 1:11
@UriP: This one might be interesting for you as it explains melatonin production with respect to light:… – Pradeep S Oct 8 '13 at 13:06

It certainly does not require full darkness. I've often slept quite restfully with the reading lamp left on all night, and children who are afraid of the dark do this habitually. However, full darkness may PROMOTE melatonin release.

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I see, thank you for your clarification. However, the main focus of my question is: Can melatonin also be released in daytime (in partial\full darkness), or only at night? – UriP Sep 27 '13 at 1:02

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