Just as solar cycle influences when we sleep, a new analysis finds that lunar cycles have some effect too. In the few days before and after a full moon, volunteers of this study took an average of 5 extra minutes to fall asleep, slept 20 minutes less per night, their delta activity (a measure of how deeply they were sleeping) was 30% lower than at other times, their level of melatonin, a sleep-related hormone, was reduced, and they reported, subjectively, that they had not slept as well as usual.
The study involved 33 volunteers who were completely isolated from daylight (and thus moonlight too). Thus, this effect must not be because of the direct effect of moonlight but instead it may be an endogenous cycle that evolution has learnt over millions of years.
Reference: C. Cajochen et al. Current Biology 2013
Further reading and Image credit: The Economist